SMART MODE:

NORMAL GENOMIC

• Wynshaw-Boris A, Gambello MJ
• LIS1 and dynein motor function in neuronal migration and development.
• Genes Dev. 2001; 15: 639-51

• Kini AR, Collins CA
• Modulation of cytoplasmic dynein ATPase activity by the accessory subunits.
• Cell Motil Cytoskeleton. 2001; 48: 52-60
• Display abstract

• The microtubule-based motor molecule cytoplasmic dynein has been proposed to be regulated by a variety of mechanisms, including phosphorylation and specific interaction with the organelle-associated complex, dynactin. In this study, we examined whether the intermediate chain subunits of cytoplasmic dynein are involved in modulation of ATP hydrolysis, and thereby affect motility. Treatment of testis cytoplasmic dynein under hypertonic salt conditions resulted in separation of the intermediate chains from the remainder of the dynein molecule, and led to a 4-fold enhancement of ATP hydrolysis. This result suggests that the accessory subunits act as negative regulators of dynein heavy chain activity. Comparison of ATPase activities of dyneins with differing intermediate chain isoforms showed significant differences in basal ATP hydrolysis rates, with testis dynein 7-fold more active than dynein from brain. Removal of the intermediate chain subunits led to an equalization of ATPase activity between brain and testis dyneins, suggesting that the accessory subunits are responsible for the observed differences in tissue activity. Finally, our preparative procedures have allowed for the identification and purification of a 1:1 complex of dynein with dynactin. As this interaction is presumed to be mediated by the dynein intermediate chain subunits, we now have defined experimental conditions for further exploration of dynein enzymatic and motility regulation.

• Lopez JC
• A smoother path to LIS1.
• Nat Rev Neurosci. 2000; 1: 157-157

• Allan V
• Dynactin.
• Curr Biol. 2000; 10: 432-432

• Adames NR, Cooper JA
• Microtubule interactions with the cell cortex causing nuclear movements in Saccharomyces cerevisiae.
• J Cell Biol. 2000; 149: 863-74
• Display abstract

• During mitosis in budding yeast the nucleus first moves to the mother-bud neck and then into the neck. Both movements depend on interactions of cytoplasmic microtubules with the cortex. We investigated the mechanism of these movements in living cells using video analysis of GFP-labeled microtubules in wild-type cells and in EB1 and Arp1 mutants, which are defective in the first and second steps, respectively. We found that nuclear movement to the neck is largely mediated by the capture of microtubule ends at one cortical region at the incipient bud site or bud tip, followed by microtubule depolymerization. Efficient microtubule interactions with the capture site require that microtubules be sufficiently long and dynamic to probe the cortex. In contrast, spindle movement into the neck is mediated by microtubule sliding along the bud cortex, which requires dynein and dynactin. Free microtubules can also slide along the cortex of both bud and mother. Capture/shrinkage of microtubule ends also contributes to nuclear movement into the neck and can serve as a backup mechanism to move the nucleus into the neck when microtubule sliding is impaired. Conversely, microtubule sliding can move the nucleus into the neck even when capture/shrinkage is impaired.

• Tromans A
• Neurobiology. Convoluted communications.
• Nature. 2000; 407: 953-953

• Minke PF, Lee IH, Tinsley JH, Plamann M
• A Neurospora crassa Arp1 mutation affecting cytoplasmic dynein and dynactin localization.
• Mol Gen Genet. 2000; 264: 433-40
• Display abstract

• Of the actin-related proteins, Arp1 is the most similar to conventional actin, and functions solely as a component of the multisubunit complex dynactin. Dynactin has been identified as an activator of the microtubule-associated motor cytoplasmic dynein. The role of Arp1 within dynactin is two-fold: (1) it serves as a structural scaffold protein for other dynactin subunits; and (2) it has been proposed to link dynactin, and thereby dynein, with membranous cargo via interaction with spectrin. Using the filamentous fungus Neurospora crassa, we have identified genes encoding subunits of cytoplasmic dynein and dynactin. In this study, we describe a genetic screen for N. crassa Arp1 (ro-4) mutants that are defective for dynactin function. We report that the ro-4(E8) mutant is unusual in that it shows alterations in the localization of cytoplasmic dynein and dynactin and in microtubule organization. In the mutant, dynein/dynactin complexes co-localize with bundled microtubules at hyphal tips. Given that dynein transports membranous cargo from hyphal tips to distal regions, the cytoplasmic dynein and dynactin complexes that accumulate along microtubule tracts at hyphal tips in the ro-4(E8) mutant may have either reduced motor activity or be delayed for activation of motor activity following cargo binding.

• Niethammer M et al.
• NUDEL is a novel Cdk5 substrate that associates with LIS1 and cytoplasmic dynein.
• Neuron. 2000; 28: 697-711
• Display abstract

• Disruption of one allele of the LIS1 gene causes a severe developmental brain abnormality, type I lissencephaly. In Aspergillus nidulans, the LIS1 homolog, NUDF, and cytoplasmic dynein are genetically linked and regulate nuclear movements during hyphal growth. Recently, we demonstrated that mammalian LIS1 regulates dynein functions. Here we characterize NUDEL, a novel LIS1-interacting protein with sequence homology to gene products also implicated in nuclear distribution in fungi. Like LIS1, NUDEL is robustly expressed in brain, enriched at centrosomes and neuronal growth cones, and interacts with cytoplasmic dynein. Furthermore, NUDEL is a substrate of Cdk5, a kinase known to be critical during neuronal migration. Inhibition of Cdk5 modifies NUDEL distribution in neurons and affects neuritic morphology. Our findings point to cross-talk between two prominent pathways that regulate neuronal migration.

• King SJ, Schroer TA
• Dynactin increases the processivity of the cytoplasmic dynein motor.
• Nat Cell Biol. 2000; 2: 20-4
• Display abstract

• Cytoplasmic dynein supports long-range intracellular movements of cargo in vivo but does not appear to be a processive motor protein by itself. We show here that the dynein activator, dynactin, binds microtubules and increases the average length of cytoplasmic-dynein-driven movements without affecting the velocity or microtubule-stimulated ATPase kinetics of cytoplasmic dynein. Enhancement of microtubule binding and motility by dynactin are both inhibited by an antibody to dynactin's microtubule-binding domain. These results indicate that dynactin acts as a processivity factor for cytoplasmic-dynein-based motility and provide the first evidence that cytoskeletal motor processivity can be affected by extrinsic factors.

• Shah JV, Flanagan LA, Janmey PA, Leterrier JF
• Bidirectional translocation of neurofilaments along microtubules mediated in part by dynein/dynactin.
• Mol Biol Cell. 2000; 11: 3495-508
• Display abstract

• Neuronal cytoskeletal elements such as neurofilaments, F-actin, and microtubules are actively translocated by an as yet unidentified mechanism. This report describes a novel interaction between neurofilaments and microtubule motor proteins that mediates the translocation of neurofilaments along microtubules in vitro. Native neurofilaments purified from spinal cord are transported along microtubules at rates of 100-1000 nm/s to both plus and minus ends. This motion requires ATP and is partially inhibited by vanadate, consistent with the activity of neurofilament-bound molecular motors. Motility is in part mediated by the dynein/dynactin motor complex and several kinesin-like proteins. This reconstituted motile system suggests how slow net movement of cytoskeletal polymers may be achieved by alternating activities of fast microtubule motors.

• Kumar S, Lee IH, Plamann M
• Cytoplasmic dynein ATPase activity is regulated by dynactin-dependent phosphorylation.
• J Biol Chem. 2000; 275: 31798-804
• Display abstract

• Cytoplasmic dynein is a microtubule-associated motor that utilizes ATP hydrolysis to conduct minus-end directed transport of various organelles. Dynactin is a multisubunit complex that has been proposed to both link dynein with cargo and activate dynein motor function. The mechanisms by which dynactin regulates dynein activity are not clear. In this study, we examine the role of dynactin in regulating dynein ATPase activity. We show that dynein-microtubule binding and ATP-dependent release of dynein from microtubules are reduced in dynactin null mutants, Deltaro-3 (p150(Glued)) and Deltaro-4 (Arp1), relative to wild-type. The dynein-microtubule binding activity, but not the ATP-dependent release of dynein from microtubules, is restored by in vitro mixing of extracts from dynein and dynactin mutants. Dynein produced in a Deltaro-3 mutant has approximately 8-fold reduced ATPase activity relative to dynein isolated from wild-type. However, dynein ATPase activity from wild-type is not reduced when dynactin is separated from dynein, suggesting that dynein produced in a dynactin mutant is inactivated. Treatment of dynein isolated from the Deltaro-3 mutant with lambda protein phosphatase restores the ATPase activity to near wild-type levels. The reduced dynein ATPase activity observed in dynactin null mutants is mainly due to altered affinity for ATP. Radiolabeling experiments revealed that low molecular mass proteins, particularly 20- and 8-kDa proteins, that immunoprecipitate with dynein heavy chain are hyperphosphorylated in the dynactin mutant and dephosphorylated upon lambda protein phosphatase treatment. The results suggest that cytoplasmic dynein ATPase activity is regulated by dynactin-dependent phosphorylation of dynein light chains.

• Vallee RB, Faulkner NE, Tai CY
• The role of cytoplasmic dynein in the human brain developmental disease lissencephaly.
• Biochim Biophys Acta. 2000; 1496: 89-98
• Display abstract

• Lissencephaly is a brain developmental disorder characterized by disorganization of the cortical regions resulting from defects in neuronal migration. Recent evidence has implicated the human LIS-1 gene in Miller-Dieker lissencephaly and isolated lissencephaly sequence. LIS-1 is homologous to the fungal genes NudF and PAC1, which are involved in cytoplasmic dynein mediated nuclear transport, but it is also almost identical to a subunit of PAF acetylhydrolase, an enzyme which inactivates the lipid mediator platelet activating factor. Recent evidence from our laboratory has revealed that cytoplasmic dynein coimmunoprecipitates with LIS-1 in bovine brain cytosol, supporting a role in the dynein pathway in vertebrates. Overexpression of LIS-1 interferes with cell division, with noteworthy effects on chromosome attachment to the mitotic spindle and on the interaction of astral microtubules with the cell cortex. Other aspects of dynein function, such as the organization of the Golgi apparatus, are not affected. Together, these results suggest a role for LIS-1 in cytoplasmic dynein functions involving microtubule plus-ends. Furthermore, they suggest that mutations in LIS-1 may produce a lissencephalic phenotype either by interfering with the movement of neuronal nuclei within extending processes, or by interference with the division cycle of neuronal progenitor cells in the ventricular and subventricular zones of the developing nervous system.

• Heald R
• A dynamic duo of microtubule modulators.
• Nat Cell Biol. 2000; 2: 112-112

• Caspi M, Atlas R, Kantor A, Sapir T, Reiner O
• Interaction between LIS1 and doublecortin, two lissencephaly gene products.
• Hum Mol Genet. 2000; 9: 2205-13
• Display abstract

• Mutations in either LIS1 or DCX are the most common cause for type I lissencephaly. Here we report that LIS1 and DCX interact physically both in vitro and in vivo. Epitope-tagged DCX transiently expressed in COS cells can be co-immunoprecipitated with endogenous LIS1. Furthermore, endogenous DCX could be co-immunoprecipitated with endogenous LIS1 in embryonic brain extracts, demonstrating an in vivo association. The two protein products also co-localize in transfected cells and in primary neuronal cells. In addition, we demonstrate homodimerization of DCX in vitro. Using fragments of both LIS1 and DCX, the domains of interaction were mapped. LIS1 and DCX interact with tubulin and microtubules. Our results suggest that addition of DCX and LIS1 to tubulin enhances polymerization in an additive fashion. In in vitro competition assays, when LIS1 is added first, DCX competes with LIS1 in its binding to microtubules, but when DCX is added prior to the addition of LIS1 it enhances the binding of LIS1 to microtubules. We conclude that LIS1 and DCX cross-talk is important to microtubule function in the developing cerebral cortex.

• Ahmad FJ, Hughey J, Wittmann T, Hyman A, Greaser M, Baas PW
• Motor proteins regulate force interactions between microtubules and microfilaments in the axon.
• Nat Cell Biol. 2000; 2: 276-80
• Display abstract

• It has long been known that microtubule depletion causes axons to retract in a microfilament-dependent manner, although it was not known whether these effects are the result of motor-generated forces on these cytoskeletal elements. Here we show that inhibition of the motor activity of cytoplasmic dynein causes the axon to retract in the presence of microtubules. This response is obliterated if microfilaments are depleted or if myosin motors are inhibited. We conclude that axonal retraction results from myosin-mediated forces on the microfilament array, and that these forces are counterbalanced or attenuated by dynein-mediated forces between the microfilament and microtubule arrays.

• Bloecher A, Venturi GM, Tatchell K
• Anaphase spindle position is monitored by the BUB2 checkpoint.
• Nat Cell Biol. 2000; 2: 556-8

• Sasaki S et al.
• A LIS1/NUDEL/cytoplasmic dynein heavy chain complex in the developing and adult nervous system.
• Neuron. 2000; 28: 681-96
• Display abstract

• Mutations in mammalian Lis1 (Pafah1b1) result in neuronal migration defects. Several lines of evidence suggest that LIS1 participates in pathways regulating microtubule function, but the molecular mechanisms are unknown. Here, we demonstrate that LIS1 directly interacts with the cytoplasmic dynein heavy chain (CDHC) and NUDEL, a murine homolog of the Aspergillus nidulans nuclear migration mutant NudE. LIS1 and NUDEL colocalize predominantly at the centrosome in early neuroblasts but redistribute to axons in association with retrograde dynein motor proteins. NUDEL is phosphorylated by Cdk5/p35, a complex essential for neuronal migration. NUDEL and LIS1 regulate the distribution of CDHC along microtubules, and establish a direct functional link between LIS1, NUDEL, and microtubule motors. These results suggest that LIS1 and NUDEL regulate CDHC activity during neuronal migration and axonal retrograde transport in a Cdk5/p35-dependent fashion.

• Liu Z, Steward R, Luo L
• Drosophila Lis1 is required for neuroblast proliferation, dendritic elaboration and axonal transport.
• Nat Cell Biol. 2000; 2: 776-83
• Display abstract

• Haplo-insufficiency of human Lis1 causes lissencephaly. Reduced Lis1 activity in both humans and mice results in a neuronal migration defect. Here we show that Drosophila Lis1 is highly expressed in the nervous system. Lis1 is essential for neuroblast proliferation and axonal transport, as shown by a mosaic analysis using a Lis1 null mutation. Moreover, it is cell-autonomously required for dendritic growth, branching and maturation. Analogous mosaic analysis shows that neurons containing a mutated cytoplasmic-dynein heavy chain (Dhc64C) exhibit phenotypes similar to Lis1 mutants. These results implicate Lis1 as a regulator of the microtubule cytoskeleton and show that it is important for diverse physiological functions in the nervous system.

• Smith DS et al.
• Regulation of cytoplasmic dynein behaviour and microtubule organization by mammalian Lis1.
• Nat Cell Biol. 2000; 2: 767-75
• Display abstract

• Whereas total loss of Lis1 is lethal, disruption of one allele of the Lis1 gene results in brain abnormalities, indicating that developing neurons are particularly sensitive to a reduction in Lis1 dosage. Here we show that Lis1 is enriched in neurons relative to levels in other cell types, and that Lis1 interacts with the microtubule motor cytoplasmic dynein. Production of more Lis1 in non-neuronal cells increases retrograde movement of cytoplasmic dynein and leads to peripheral accumulation of microtubules. These changes may reflect neuron-like dynein behaviours induced by abundant Lis1. Lis1 deficiency produces the opposite phenotype. Our results indicate that abundance of Lis1 in neurons may stimulate specific dynein functions that function in neuronal migration and axon growth.

• Karki S, Holzbaur EL
• Cytoplasmic dynein and dynactin in cell division and intracellular transport.
• Curr Opin Cell Biol. 1999; 11: 45-53
• Display abstract

• Since the initial discovery of cytoplasmic dynein, it has become apparent that this microtubule-based motor is involved in several cellular functions including cell division and intracellular transport. Another multisubunit complex, dynactin, may be required for most, if not all, cytoplasmic dynein-driven activities and may provide clues to dynein's functional diversity. Recent genetic and biochemical findings have illuminated the cellular roles of dynein and dynactin and provided insight into the functional mechanism of this complex motor.

• Bingham JB, King SJ, Schroer TA
• Purification of dynactin and dynein from brain tissue.
• Methods Enzymol. 1998; 298: 171-84

• Ahmad FJ, Echeverri CJ, Vallee RB, Baas PW
• Cytoplasmic dynein and dynactin are required for the transport of microtubules into the axon.
• J Cell Biol. 1998; 140: 391-401
• Display abstract

• Previous work from our laboratory suggested that microtubules are released from the neuronal centrosome and then transported into the axon (Ahmad, F.J., and P.W. Baas. 1995. J. Cell Sci. 108: 2761-2769). In these studies, cultured sympathetic neurons were treated with nocodazole to depolymerize most of their microtubule polymer, rinsed free of the drug for a few minutes to permit a burst of microtubule assembly from the centrosome, and then exposed to nanomolar levels of vinblastine to suppress further microtubule assembly from occurring. Over time, the microtubules appeared first near the centrosome, then dispersed throughout the cytoplasm, and finally concentrated beneath the periphery of the cell body and within developing axons. In the present study, we microinjected fluorescent tubulin into the neurons at the time of the vinblastine treatment. Fluorescent tubulin was not detected in the microtubules over the time frame of the experiment, confirming that the redistribution of microtubules observed with the experimental regime reflects microtubule transport rather than microtubule assembly. To determine whether cytoplasmic dynein is the motor protein that drives this transport, we experimentally increased the levels of the dynamitin subunit of dynactin within the neurons. Dynactin, a complex of proteins that mediates the interaction of cytoplasmic dynein and its cargo, dissociates under these conditions, resulting in a cessation of all functions of the motor tested to date (Echeverri, C.J., B.M. Paschal, K.T. Vaughan, and R.B. Vallee. 1996. J. Cell Biol. 132: 617-633). In the presence of excess dynamitin, the microtubules did not show the outward progression but instead remained near the centrosome or dispersed throughout the cytoplasm. On the basis of these results, we conclude that cytoplasmic dynein and dynactin are essential for the transport of microtubules from the centrosome into the axon.

• Merdes A, Cleveland DW
• Pathways of spindle pole formation: different mechanisms; conserved components.
• J Cell Biol. 1997; 138: 953-6

• Ulitzur N, Humbert M, Pfeffer SR
• Mapmodulin: a possible modulator of the interaction of microtubule-associated proteins with microtubules.
• Proc Natl Acad Sci U S A. 1997; 94: 5084-9
• Display abstract

• We have purified and characterized a 31-kDa protein named mapmodulin that binds to the microtubule-associated proteins (MAPs) MAP2, MAP4, and tau. Mapmodulin binds free MAPs in strong preference to microtubule-associated MAPs, and appears to do so via the MAP's tubulin-binding domain. Mapmodulin inhibits the initial rate of MAP2 binding to microtubules, a property that may allow mapmodulin to displace MAPs from the path of organelles translocating along microtubules. In support of this possibility, mapmodulin stimulates the microtubule- and dynein-dependent localization of Golgi complexes in semi-intact CHO cells. To our knowledge, mapmodulin represents the first example of a protein that can bind and potentially regulate multiple MAP proteins.

• Allan V
• Motor proteins: a dynamic duo.
• Curr Biol. 1996; 6: 630-3
• Display abstract

• The interactions between the microtubule motor cytoplasmic dynein and its putative regulator dynactin have been shown to be dynamic and complex.

• Toyoshima H
• [Control of cell cycle by the p27 Cdk-inhibitor]
• Tanpakushitsu Kakusan Koso. 1996; 41: 1732-6

• Dillman JF 3rd, Pfister KK
• Differential phosphorylation in vivo of cytoplasmic dynein in anterograde and whole cell compartments.
• Biophys J. 1995; 68: 226-226

• Asai DJ
• Multi-dynein hypothesis.
• Cell Motil Cytoskeleton. 1995; 32: 129-32
• Display abstract

• Axonemal dyneins and cytoplasmic dynein have evolved separate strategies to perform their tasks. The multi-dynein hypothesis accurately describes the highly specialized axonemal isoforms; each isoform is encoded by a separate gene, is located in a precise place, produces specific forces which contribute to the overall generation of propagated bending, and is not functionally interchangeable with other isoforms. In contrast, cytoplasmic dynein, although carrying many different cargoes, appears to be one isoform. An intriguing question is to determine whether there are additional cytoplasmic dyneins, heretofore uncharacterized, which, like their axonemal counterparts, are customized to perform specific tasks.

• McGrail M, Gepner J, Silvanovich A, Ludmann S, Serr M, Hays TS
• Regulation of cytoplasmic dynein function in vivo by the Drosophila Glued complex.
• J Cell Biol. 1995; 131: 411-25
• Display abstract

• The Drosophila Glued gene product shares sequence homology with the p150 component of vertebrate dynactin. Dynactin is a multiprotein complex that stimulates cytoplasmic dynein-mediated vesicle motility in vitro. In this report, we present biochemical, cytological, and genetic evidence that demonstrates a functional similarity between the Drosophila Glued complex and vertebrate dynactin. We show that, similar to the vertebrate homologues in dynactin, the Glued polypeptides are components of a 20S complex. Our biochemical studies further reveal differential expression of the Glued polypeptides, all of which copurify as microtubule-associated proteins. In our analysis of the Glued polypeptides encoded by the dominant mutation, Glued, we identify a truncated polypeptide that fails to assemble into the wild-type 20S complex, but retains the ability to copurify with microtubules. The spatial and temporal distribution of the Glued complex during oogenesis is shown by immunocytochemistry methods to be identical to the pattern previously described for cytoplasmic dynein. Significantly, the pattern of Glued distribution in oogenesis is dependent on dynein function, as well as several other gene products known to be required for proper dynein localization. In genetic complementation studies, we find that certain mutations in the cytoplasmic dynein heavy chain gene Dhc64C act as dominant suppressors or enhancers of the rough eye phenotype of the dominant Glued mutation. Furthermore, we show that a mutation that was previously isolated as a suppressor of the Glued mutation is an allele of Dhc64C. Together with the observed dependency of Glued localization on dynein function, these genetic interactions demonstrate a functional association between the Drosophila dynein motor and Glued complexes.

• Hagiwara H, Yorifuji H, Sato-Yoshitake R, Hirokawa N
• Competition between motor molecules (kinesin and cytoplasmic dynein) and fibrous microtubule-associated proteins in binding to microtubules.
• J Biol Chem. 1994; 269: 3581-9
• Display abstract

• In neuronal cells, microtubule-associated proteins (MAPs) can be classified into two distinct groups. One consists of force-producing MAPs, the main components of which are kinesin and cytoplasmic dynein. The other is composed of fibrous MAPs, which include tau and MAP2. Many studies have been performed on the respective groups to understand their structures and functions. However, the problem of how the groups interact with each other on microtubules is still unresolved. To elucidate the interaction between kinesin or cytoplasmic dynein and tau or MAP2, we performed three experiments: competition, motility assay, and cosedimentation. To distinguish whether the binding competition is caused by steric hindrance of the projection domains of MAPs or by the competition of the binding sites on microtubules, we used microtubule binding domains of tau and MAP2 as well as native proteins. Our results revealed that kinesin or cytoplasmic dynein and tau or MAP2 complete for almost the same binding domains located on the carboxyl-terminal side of alpha- and the amino-terminal side of beta-tubulin from the site of subtilisin cleavage. Furthermore, the projection of tau, and probably of MAP2, might inhibit the binding of kinesin or cytoplasmic dynein to microtubules by steric hindrance. These findings will provide a useful step toward understanding the regulation system of intracellular organelle transport.

• Murofushi H
• [Microtubule-associated proteins]
• Seikagaku. 1993; 65: 1321-7

• Holzbaur EL, Hammarback JA, Paschal BM, Kravit NG, Pfister KK, Vallee RB
• Homology of a 150K cytoplasmic dynein-associated polypeptide with the Drosophila gene Glued.
• Nature. 1992; 360: 695-695

• Wiche G, Oberkanins C, Himmler A
• Molecular structure and function of microtubule-associated proteins.
• Int Rev Cytol. 1991; 124: 217-73

• Olmsted JB
• Non-motor microtubule-associated proteins.
• Curr Opin Cell Biol. 1991; 3: 52-8
• Display abstract

• Cloning of primary sequences has generated information on the structures of the non-motor microtubule-associated proteins and their relationship to one another. Questions about how classes of microtubule-associated proteins interact are starting to be addressed in vitro and, in vivo, tests of function are being pursued using a variety of cellular and molecular biological strategies.

• Cleveland DW, Joshi HC, Murphy DB
• Tubulin site interpretation.
• Nature. 1990; 344: 389-389

• Leterrier JF, Linden M, Nelson BD
• How do microtubules interact in vitro with purified subcellular organelles?
• Biochem J. 1990; 269: 556-8

• Lewis SA, Cowan N
• Microtubule bundling.
• Nature. 1990; 345: 674-674

• Sorochinskii BV, Prokhnevskii AI, Grodzinskii DM
• [Modification by taxol of the assembly of irradiated microtubules]
• Dokl Akad Nauk SSSR. 1990; 310: 735-7

• Rodionov VI, Gyoeva FK, Kashina AS, Kuznetsov SA, Gelfand VI
• Microtubule-associated proteins and microtubule-based translocators have different binding sites on tubulin molecule.
• J Biol Chem. 1990; 265: 5702-7
• Display abstract

• It has been previously shown that a class of microtubule proteins, the so-called microtubule-associated proteins (MAPs), binds to the C-terminal part of tubulin subunits. We show here that microtubules composed of tubulin whose 4-kDa C-terminal domain was cleaved by subtilisin (S-microtubules) are unable to bind MAPs but can still bind the anterograde translocator protein kinesin and the retrograde translocator dynein. Binding of both motors to S-microtubules, like their binding to normal microtubules, was ATP-dependent. In addition, direct competition experiments showed that binding sites for kiensin and MAPs on the microtubule surface lattice do not overlap. Furthermore, S-microtubules stimulated the ATPase activity of kinesin at least 8-fold, and the affinities of kinesin for control and S-microtubules were identical. S-microtubules were able to glide along kinesin-coated coverslips at a rate of 0.2 microns/s, the same rate as control microtubules. We conclude, that unlike MAPs, kinesin and cytoplasmic dynein bind to the tubulin molecule outside the C-terminal region.

• Eyer J, White D, Gagnon C
• Presence of a new microtubule cold-stabilizing factor in bull sperm dynein preparations.
• Biochem J. 1990; 270: 821-4
• Display abstract

• Brain tubulin polymerized with dynein isolated from bull spermatozoa forms cold-stable microtubules, in contrast with microtubules made of brain tubulin polymerized by brain microtubule-associated proteins (MAPs). The level of cold-stable microtubules depends on the concentration of dynein used. Addition of dynein to cold-unstable microtubules renders these microtubules stable to cold. Although ATP and a non-hydrolysable ATP analogue increase the formation of microtubules made of tubulin and dynein, these nucleotides have no effect on dynein cold-stabilizing properties. The data suggests that a new factor, not involving the dynein ATPase active site and present in bull sperm dynein preparations, confers cold-stability to microtubules.

• Vallee RB, Shpetner HS, Paschal BM
• Potential roles of microtubule-associated motor molecules in cell division.
• Ann N Y Acad Sci. 1990; 582: 99-107

• Rendon A, Jung D, Jancsik V
• Interaction of microtubules and microtubule-associated proteins (MAPs) with rat brain mitochondria.
• Biochem J. 1990; 269: 555-6

• Cleveland DW
• Microtubule MAPping.
• Cell. 1990; 60: 701-2

• Vallee RB, Shpetner HS, Paschal BM
• The role of dynein and other microtubule-activated ATPases in mitosis.
• Prog Clin Biol Res. 1989; 318: 205-15

• Paschal BM, Obar RA, Vallee RB
• Interaction of brain cytoplasmic dynein and MAP2 with a common sequence at the C terminus of tubulin.
• Nature. 1989; 342: 569-72
• Display abstract

• Two main types of microtubule-associated proteins (MAPs) have been identified in neuronal cells. The fibrous MAPs, including MAP2 and tau, serve to organize and regulate the assembly of microtubules. A second distinct class of force-producing MAPs, including kinesin, dynein and dynamin, are involved in microtubule-based movement. These proteins are mechanochemical ATPases which seem to be responsible for the bidirectional transport of organelles and perhaps also the movement of chromosomes. Here we report that MAP2 inhibits microtubule gliding on dynein-coated coverslips, as well as the microtubule-activated ATPase of dynein, indicating that MAP2 and other fibrous MAPs could be important modulators of microtubule-based motility in vivo. By proteolytic modification of tubulin, we found that dynein interacts with microtubules at the C termini of alpha- and beta-tubulin, the regions previously reported to be the sites for the interaction of MAP2. The use of site-directed antibodies implicates a small region of alpha- and beta-tubulin, containing the sequence Glu-Gly-Glu-Glu, as the site of the interaction of dynein and MAP2 with the microtubule.

• Matus A
• Microtubule-associated proteins: their potential role in determining neuronal morphology.
• Annu Rev Neurosci. 1988; 11: 29-44

• Vallee RB, Wall JS, Paschal BM, Shpetner HS
• Microtubule-associated protein 1C from brain is a two-headed cytosolic dynein.
• Nature. 1988; 332: 561-3
• Display abstract

• Dynein, an ATPase, is the force-generating protein in cilia and flagella. It has long been speculated that cytoplasmic microtubules contain a related enzyme involved in cell division or in intracellular organelle transport. A 'cytoplasmic dynein' has been described in sea urchin eggs, but because the egg stockpiles precursors for both cytoplasmic and ciliary microtubules, the role of this enzyme in the cell has remained unresolved. We recently found that the microtubule-associated protein (MAP) 1C (ref. 6) from brain is a microtubule-activated ATPase that produces force in the direction corresponding to retrograde organelle transport in the cell. MAP 1C has several similar properties to ciliary and flagellar dynein. Here we show directly, using scanning transmission electron microscopy, that MAP 1C is structurally equivalent to the ciliary and flagellar enzyme and is the long-sought cytoplasmic analogue of this enzyme.

• Paschal BM, Shpetner HS, Vallee RB
• MAP 1C is a microtubule-activated ATPase which translocates microtubules in vitro and has dynein-like properties.
• J Cell Biol. 1987; 105: 1273-82
• Display abstract

• We observe that one of the high molecular mass microtubule-associated proteins (MAPs) from brain exhibits nucleotide-dependent binding to microtubules. We identify the protein as MAP IC, which was previously described in this laboratory as a minor component of standard microtubule preparations (Bloom, G.S., T. Schoenfeld, and R.B. Vallee, 1984, J. Cell Biol., 98:320-330). We find that MAP 1C is enriched in microtubules prepared in the absence of nucleotide. Kinesin is also found in these preparations, but can be specifically extracted with GTP. A fraction highly enriched in MAP 1C can be prepared by subsequent extraction of the microtubules with ATP. Two activities cofractionate with MAP 1C upon further purification, a microtubule-activated ATPase activity and a microtubule-translocating activity. These activities indicate a role for the protein in cytoplasmic motility. MAP 1C coelectrophoreses with the beta heavy chain of Chlamydomonas flagellar dynein, and has a sedimentation coefficient of 20S. Exposure to ultraviolet light in the presence of vanadate and ATP results in the production of two large fragments of MAP 1C. These characteristics suggest that MAP 1C may be a cytoplasmic analogue of axonemal dynein.

• Solomon F
• Direct identification of microtubule-associated proteins by selective extraction of cultured cells.
• Methods Enzymol. 1986; 134: 139-47

• Asai DJ, Leslie RJ, Wilson L
• Dynein-like cytoplasmic microtubule translocators.
• Ann N Y Acad Sci. 1986; 466: 275-91
• Display abstract

• The eukaryotic flagellum presents an excellent predictive model of microtubule-mediated motility: movement is caused by microtubule translocators, called dyneins, which actively slide outer doublet microtubules against each other. Cytoplasmic movements, such as certain aspects of mitotic motion, may also be powered by dynein-like molecules. It is important, then, to carefully assess potential cytoplasmic dynein-like translocators by applying criteria defined by the properties of axonemal dynein. A cytoplasmic microtubule translocator may be only partially homologous to axonemal dynein; a modular construction may provide the translocator with domains that are shared with dynein, and with other domains that give it functional specificity. Finally, it is important to consider the possibility that a dynein-like enzyme that is found in the cytoplasm may not function in the cytoplasm but rather is awaiting incorporation into an axoneme.

• Satir P, Avolio J
• Dynein as a microtubule-associated protein.
• Ann N Y Acad Sci. 1986; 466: 269-74

• Hameroff SR, Smith SA, Watt RC
• Automaton model of dynamic organization in microtubules.
• Ann N Y Acad Sci. 1986; 466: 949-52

• Olmsted JB
• Microtubule-associated proteins.
• Annu Rev Cell Biol. 1986; 2: 421-57

• Murphy DB, Hiebsch RR, Wallis KT
• Identity and Origin of the ATPase activity associated with neuronal microtubules. I. The ATPase activity is associated with membrane vesicles.
• J Cell Biol. 1983; 96: 1298-305
• Display abstract

• Microtubule protein purified from brain tissue by cycles of in vitro assembly-disassembly contains ATPase activity that has been postulated to be associated with microtubule-associated proteins (MAPs) and therefore significant for studies of microtubule-dependent motility. In this paper we demonstrate that greater than 90% of the ATPase activity is particulate in nature and may be derived from contaminating membrane vesicles. We also show that the MAPs (MAP-1, MAP-2, and tau factors) and other high molecular weight polypeptides do not contain significant amounts of ATPase activity. These findings do not support the concept of "brain dynein" or of MAPs with ATPase activity.

• Haimo LT, Rosenbaum JL
• Dynein binding to microtubules containing microtubule-associated proteins.
• Cell Motil. 1981; 1: 499-516
• Display abstract

• Microtubule-associated proteins (MAPs), isolated from brain tubulin, bound to and saturated outer fibers of Chlamydomonas flagella. MAPs present on these microtubules prevented the subsequent recombination of dynein. MAPs also bound to intact axonemes and thus did not specifically bind to the dynein binding sites on the A subfiber. A molar ratio of 1 mole MAP2 per 27 moles tubulin dimers at saturation of the outer fibers with MAP2 suggested that MAPs could effectively interfere with dynein recombination only if the MAPs were near the dynein binding sites to sterically prevent binding. However, electron microscopic observations indicated that MAPs were not localized but, instead, were dispersed around the outer fibers. In addition, MAP2 present at saturating amounts on in vitro assembled brain microtubules had no significant effect on dynein binding. Dynein-decorated microtubules contained clusters of arms suggesting that there may be cooperative interaction between the arms during dynein binding. Because the A subfiber of axonemes contains sites to which dynein preferentially attaches, MAPs may prevent recombination by interfering with cooperative binding to these specific sites. Dynein presumably binds with equal affinity to any protofilament on in vitro assembled microtubules, and, therefore, the MAPs may not be capable of effectively interfering with cooperative binding of dynein to these microtubules.

• Haimo LT, Rosenbaum JL
• Cilia, flagella, and microtubules.
• J Cell Biol. 1981; 91: 125130-125130

• Pollard TD
• Which organelles are necessary for fast neuronal transport?
• Neurosci Res Program Bull. 1981; 20: 92-7

© 2021 EMBL | Privacy Policy