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Yoshimura A, Fujii R, Watanabe Y, Okabe S, Fukui K, Takumi T. Myosin-Va facilitates the accumulation of mRNA/protein complex in dendritic spines. Curr Biol 2007; 16:2345-51. [PMID: 17141617 DOI: 10.1016/j.cub.2006.10.024] [Citation(s) in RCA: 142] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2006] [Revised: 09/17/2006] [Accepted: 10/05/2006] [Indexed: 11/15/2022]
Abstract
mRNA localization has an essential role in localizing cytoplasmic determinants, controlling the direction of protein secretion, and allowing the local control of protein synthesis in neurons. In neuronal dendrites, the localization and translocation of mRNA is considered as one of the molecular bases of synaptic plasticity. Recent imaging and functional studies revealed that several RNA-binding proteins form a large messenger ribonucleoprotein (mRNP) complex that is involved in transport and translation of mRNA in dendrites. However, the mechanism of mRNA translocation into dendritic spines is unknown. Here, we show that an actin-based motor, myosin-Va, plays a significant role in mRNP transport in neuronal dendrites and spines. Myosin-Va was Ca2+-dependently associated with TLS, an RNA-binding protein, and its target RNA Nd1-L, an actin stabilizer. A dominant-negative mutant or RNAi of myosin-Va in neurons suppressed TLS accumulation in spines and further impaired TLS dynamics upon activation of mGluRs. The TLS translocation into spines was impeded also in neurons prepared from myosin-Va-null dilute-lethal (dl) mice, which exhibit neurological defects. Our results demonstrate that myosin-Va facilitates the transport of TLS-containing mRNP complexes in spines and may function in synaptic plasticity through Ca2+ signaling.
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52
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Dürrwang U, Fujita-Becker S, Erent M, Kull FJ, Tsiavaliaris G, Geeves MA, Manstein DJ. Dictyostelium myosin-IE is a fast molecular motor involved in phagocytosis. J Cell Sci 2006; 119:550-8. [PMID: 16443752 DOI: 10.1242/jcs.02774] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Class I myosins are single-headed motor proteins, implicated in various motile processes including organelle translocation, ion-channel gating, and cytoskeleton reorganization. Here we describe the cellular localization of myosin-IE and its role in the phagocytic uptake of solid particles and cells. A complete analysis of the kinetic and motor properties of Dictyostelium discoideum myosin-IE was achieved by the use of motor domain constructs with artificial lever arms. Class I myosins belonging to subclass IC like myosin-IE are thought to be tuned for tension maintenance or stress sensing. In contrast to this prediction, our results show myosin-IE to be a fast motor. Myosin-IE motor activity is regulated by myosin heavy chain phosphorylation, which increases the coupling efficiency between the actin and nucleotide binding sites tenfold and the motile activity more than fivefold. Changes in the level of free Mg(2+) ions, which are within the physiological range, are shown to modulate the motor activity of myosin-IE by inhibiting the release of adenosine diphosphate.
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Affiliation(s)
- Ulrike Dürrwang
- Abteilung Biophysik, Max-Planck Institut für medizinische Forschung, Jahnstr. 29, 69120 Heidelberg, Germany
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53
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Abstract
Myosin-V is a linear molecular motor that hydrolyzes ATP to move processively toward the plus end of actin filaments. Motion of this motor under low forces has been studied recently in various single-molecule assays. In this paper we show that myosin-V reacts to high forces as a mechanical ratchet. High backward loads can induce rapid and processive backward steps along the actin filament. This motion is completely independent of ATP binding and hydrolysis. In contrast, forward forces cannot induce ATP-independent forward steps. We can explain this pronounced mechanical asymmetry by a model in which the strength of actin binding of a motor head is modulated by the lever arm conformation. Knowledge of the complete force-velocity dependence of molecular motors is important to understand their function in the cellular environment.
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Affiliation(s)
- J. Christof M. Gebhardt
- Physics Department E22, Technical University of Munich, James-Franck-Strasse, D-85748 Garching, Germany
| | - Anabel E.-M. Clemen
- Physics Department E22, Technical University of Munich, James-Franck-Strasse, D-85748 Garching, Germany
| | - Johann Jaud
- Physics Department E22, Technical University of Munich, James-Franck-Strasse, D-85748 Garching, Germany
| | - Matthias Rief
- Physics Department E22, Technical University of Munich, James-Franck-Strasse, D-85748 Garching, Germany
- *To whom correspondence should be addressed. E-mail:
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54
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Guydosh NR, Block SM. Backsteps induced by nucleotide analogs suggest the front head of kinesin is gated by strain. Proc Natl Acad Sci U S A 2006; 103:8054-9. [PMID: 16698928 PMCID: PMC1472428 DOI: 10.1073/pnas.0600931103] [Citation(s) in RCA: 118] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The two-headed kinesin motor harnesses the energy of ATP hydrolysis to take 8-nm steps, walking processively along a microtubule, alternately stepping with each of its catalytic heads in a hand-over-hand fashion. Two persistent challenges for models of kinesin motility are to explain how the two heads are coordinated ("gated") and when the translocation step occurs relative to other events in the mechanochemical reaction cycle. To investigate these questions, we used a precision optical trap to measure the single-molecule kinetics of kinesin in the presence of substrate analogs beryllium fluoride or adenylyl-imidodiphosphate. We found that normal stepping patterns were interspersed with long pauses induced by analog binding, and that these pauses were interrupted by short-lived backsteps. After a pause, processive stepping could only resume once the kinesin molecule took an obligatory, terminal backstep, exchanging the positions of its front and rear heads, presumably to allow release of the bound analog from the new front head. Preferential release from the front head implies that the kinetics of the two heads are differentially affected when both are bound to the microtubule, presumably by internal strain that is responsible for the gating. Furthermore, we found that ATP binding was required to reinitiate processive stepping after the terminal backstep. Together, our results support stepping models in which ATP binding triggers the mechanical step and the front head is gated by strain.
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Affiliation(s)
| | - Steven M. Block
- Biological Sciences and
- Applied Physics, Stanford University, Stanford, CA 94305
- To whom correspondence should be addressed. E-mail:
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55
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Abstract
The cytoplasm of cells is teaming with vesicles and other cargo that are moving along tracks of microtubules or actin filaments, powered by myosins, kinesins and dyneins. Myosin V has been implicated in several types of intracellular transport. The mechanism by which myosin V moves processively along actin filaments has been the subject of many biophysical and biochemical studies and a consensus is starting to emerge about how this minute molecular motor operates.
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Affiliation(s)
- James R Sellers
- Laboratory of Molecular Physiology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892-1762, USA.
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56
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Sun M, Oakes JL, Ananthanarayanan SK, Hawley KH, Tsien RY, Adams SR, Yengo CM. Dynamics of the upper 50-kDa domain of myosin V examined with fluorescence resonance energy transfer. J Biol Chem 2005; 281:5711-7. [PMID: 16377637 DOI: 10.1074/jbc.m508103200] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The upper 50-kDa region of myosin may be critical for coupling between the nucleotide- and actin-binding regions. We introduced a tetracysteine motif in the upper 50-kDa domain (residues 292-297) of myosin V containing a single IQ domain (MV 1IQ), allowing us to label this site with the fluorescein biarscenical hairpin-binding dye (FlAsH) (MV 1IQ FlAsH). The enzymatic properties of MV 1IQ FlAsH were similar to those of unlabeled MV 1IQ except for a 3-fold reduced ADP-release rate. MV 1IQ FlAsH was also capable of moving actin filaments in the in vitro motility assay. To examine rotation of the upper 50-kDa region, we determined the difference in the degree of energy transfer from N-methylanthraniloyl (mant)-labeled nucleotides to FlAsH in both steady-state and transient kinetic experiments. The energy transfer efficiency was higher with mant-ATP (0.65 +/- 0.02) compared with mant-ADP (0.55 +/- 0.02) in the absence of actin. Stopped-flow measurements suggested that the energy transfer efficiency decreased with phosphate release (0.04 s(-1)) in the absence of actin. In contrast, upon mixing MV 1IQ FlAsH in the ADP.P(i) state with actin, a decrease in the energy transfer signal was observed at a rate of 13 s(-1), similar to the ADP release rate. Our results demonstrate there was no change in the energy transfer signal upon actin-activated phosphate release and suggest that actin binding alters the dynamics of the upper 50-kDa region, which may be critical for the ability of myosin to bind tightly to both ADP and actin.
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Affiliation(s)
- Mingxuan Sun
- Department of Biology, University of North Carolina, Charlotte, NC 28223, USA
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57
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Nyitrai M, Rossi R, Adamek N, Pellegrino MA, Bottinelli R, Geeves MA. What limits the velocity of fast-skeletal muscle contraction in mammals? J Mol Biol 2005; 355:432-42. [PMID: 16325202 DOI: 10.1016/j.jmb.2005.10.063] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2005] [Revised: 10/17/2005] [Accepted: 10/24/2005] [Indexed: 10/25/2022]
Abstract
In rat skeletal muscle the unloaded shortening velocity (Vo) is defined by the myosin isoform expressed in the muscle fibre. In 2001 we suggested that ADP release from actomyosin in solution (controlled by k(-AD)) was of the right size to limit Vo. However, to compare mechanical and solution kinetic data required a series of corrections to compensate for the differences in experimental conditions (0.5 M KCl, 22 degrees C for kinetic assays of myosin, 200 mM ionic strength, 12 degrees C to measure Vo). Here, a method was developed to prepare heavy meromyosin (HMM) from pure myosin isoforms isolated from single muscle fibres and to study k(-AD) (determined from the affinity of the acto-myosin complex for ADP, KAD) and the rate of ATP-induced acto-HMM dissociation (controlled by K1k+2) under the same experimental condition used to measure Vo). In fast-muscle myosin isolated from a wide range of mammalian muscles, k(-AD) was found to be too fast to limit Vo, whereas K1k+2 was of the right magnitude for ATP-induced dissociation of the cross-bridge to limit shortening velocity. The result was unexpected and prompted further experiments using the stopped-flow approach on myosin subfragment-1 (S1) and HMM obtained from bulk preparations of rabbit and rat muscle. These confirmed that the rate of cross-bridge dissociation by ATP limits the velocity of contraction for fast myosin II isoforms at 12 degrees C, while k(-AD) limits the velocity of slow myosin II isoforms. Extrapolating our data to 37 degrees C suggests that at physiological temperature the rate of ADP dissociation may limit Vo for both isoforms.
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Affiliation(s)
- Miklós Nyitrai
- Department of Biophysics, University of Pécs, Pecs, Hungary
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58
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Affiliation(s)
- Adrian O Olivares
- Department of Molecular Biophysics and Biochemistry, Yale University, P.O. Box 208114, New Haven, CT 06520-8114, USA
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59
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Purcell TJ, Sweeney HL, Spudich JA. A force-dependent state controls the coordination of processive myosin V. Proc Natl Acad Sci U S A 2005; 102:13873-8. [PMID: 16150709 PMCID: PMC1236568 DOI: 10.1073/pnas.0506441102] [Citation(s) in RCA: 145] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Myosin V is an efficient processive molecular motor. Recent experiments have shown how the structure and kinetics of myosin V are specialized to produce a highly processive motor capable of taking multiple 36-nm steps on an actin filament track. Here, we examine how two identical heads coordinate their activity to produce efficient hand-over-hand stepping. We have used a modified laser-trap microscope to apply a approximately 2-pN forward or backward force on a single-headed myosin V molecule, hypothesized to simulate forces experienced by the rear or lead head, respectively. We found that pulling forward produces only a small change in the kinetics, whereas pulling backward induces a large reduction in the cycling of the head. These results support a model in which the coordination of myosin V stepping is mediated by strain-generated inhibition of the lead head.
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Affiliation(s)
- Thomas J Purcell
- Department of Biochemistry, Stanford University Medical Center, Stanford, CA 94305, USA
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Ménétrey J, Bahloul A, Wells A, Yengo C, Morris C, Sweeney HL, Houdusse A. The structure of the myosin VI motor reveals the mechanism of directionality reversal. Nature 2005; 435:779-85. [PMID: 15944696 PMCID: PMC2762700 DOI: 10.1038/nature03592] [Citation(s) in RCA: 165] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2005] [Accepted: 04/01/2005] [Indexed: 11/09/2022]
Abstract
Here we solve a 2.4-A structure of a truncated version of the reverse-direction myosin motor, myosin VI, that contains the motor domain and binding sites for two calmodulin molecules. The structure reveals only minor differences in the motor domain from that in plus-end directed myosins, with the exception of two unique inserts. The first is near the nucleotide-binding pocket and alters the rates of nucleotide association and dissociation. The second unique insert forms an integral part of the myosin VI converter domain along with a calmodulin bound to a novel target motif within the insert. This serves to redirect the effective 'lever arm' of myosin VI, which includes a second calmodulin bound to an 'IQ motif', towards the pointed (minus) end of the actin filament. This repositioning largely accounts for the reverse directionality of this class of myosin motors. We propose a model incorporating a kinesin-like uncoupling/docking mechanism to provide a full explanation of the movements of myosin VI.
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Affiliation(s)
- Julie Ménétrey
- Structural Motility, Institut Curie CNRS, UMR144, 26 rue d’Ulm, 75248 Paris cedex 05, France
| | - Amel Bahloul
- Structural Motility, Institut Curie CNRS, UMR144, 26 rue d’Ulm, 75248 Paris cedex 05, France
| | - Amber Wells
- Department of Physiology, University of Pennsylvania School of Medicine, 3700 Hamilton Walk, Philadelphia, PA 19104-6085 USA
| | - Christopher Yengo
- Department of Physiology, University of Pennsylvania School of Medicine, 3700 Hamilton Walk, Philadelphia, PA 19104-6085 USA
| | - Carl Morris
- Department of Physiology, University of Pennsylvania School of Medicine, 3700 Hamilton Walk, Philadelphia, PA 19104-6085 USA
| | - H. Lee Sweeney
- Department of Physiology, University of Pennsylvania School of Medicine, 3700 Hamilton Walk, Philadelphia, PA 19104-6085 USA
| | - Anne Houdusse
- Structural Motility, Institut Curie CNRS, UMR144, 26 rue d’Ulm, 75248 Paris cedex 05, France
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61
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Geeves MA, Holmes KC. The Molecular Mechanism of Muscle Contraction. ADVANCES IN PROTEIN CHEMISTRY 2005; 71:161-93. [PMID: 16230112 DOI: 10.1016/s0065-3233(04)71005-0] [Citation(s) in RCA: 272] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Affiliation(s)
- Michael A Geeves
- Department of Biosciences, University of Kent, Canterbury, Kent CT2 7NJ, United Kingdom
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