Molecular motors drive key biological processes such as intracellular cargo transport and cell division. Two dimeric motors, kinesin and cytoplasmic dynein, can take many consecutive steps along microtubules to transport cargos over long distances. This continuous movement, termed processivity, requires coordination between the two motor domains to prevent premature release from the microtubule. Detailed structural and mechanistic models exist for kinesin, but the mechanism and coordination of dynein motility remains largely unknown. Dynein's unconventional structure and distinct origin suggest that it has different mechanistic features than other cytoskeletal motors. Dynein forms a large multisubunit complex, the core of which consists of a ring of AAA ATPase domains. Conformational changes driven by ATP hydrolysis within the ring underlie dynein force generation and motion. Recent structural and biochemical studies have identified the major conformational states of monomeric dynein constructs. However, studies of active dynein dimers are lacking. As a result, the molecular basis by which ATP driven structural changes lead to unidirectional motion of a dimer as a whole is unknown. In our preliminary work, we have used S. cerevisiae to express recombinant dynein motors and characterized dynein stepping behavior in vitro. In this proposal, using single-molecule imaging methods, we propose to dissect the coordination between the nucleotide and conformational states of the motor domains in native and engineered dynein constructs. We have three specific aims. First, using multicolor tracking methods, we will directly observe how the AAA ring domains coordinate their nucleotide cycles and move relative to each other. The specific roles of distinct AAA domains will be studied by selectively mutating out the ATPase sites in one ring. Second, we will investigate how ATP-driven conformational states of the motor domain drive the dynein powerstroke and alter microtubule-binding affinity. The ability to perform these measurements as dynein walks will allow us to demonstrate whether the mechanical cycle of one head is gated until the other head completes its forward step. Third, we will establish the structural basis of dynein's minus-end directionality. Together, our proposed research represents a focused investigation of the conformational and chemical states of dynein at a single-molecule level, as active dynein dimers move along surface-immobilized MTs. We hope to significantly advance understanding of dynein's fundamental mechanochemistry and learn how it achieves retrograde transport of intracellular cargos.
Consistent with its fundamental roles in neurobiology and cell development, complete knockouts of dynein stop the entire microtubule transport machinery and inhibit mitosis. Mutations that alter the processivity or velocity of dynein movement lead to pathogenesis of motor neuron degeneration, including the Alzheimer's disease and ALS. Detailed studies of dynein-related diseases require replacement of engineered dynein mutants whose motility properties have been altered in predictable ways. Dissecting the mechanism of dynein motility is a prerequisite of understanding the molecular basis of these diseases.
|Urnavicius, Linas; Lau, Clinton K; Elshenawy, Mohamed M et al. (2018) Cryo-EM shows how dynactin recruits two dyneins for faster movement. Nature 554:202-206|
|Fu, Guo; Bandaria, Jigar N; Le Gall, Anne Valérie et al. (2018) MotAB-like machinery drives the movement of MreB filaments during bacterial gliding motility. Proc Natl Acad Sci U S A 115:2484-2489|
|Belyy, Vladislav; Shih, Sheng-Min; Bandaria, Jigar et al. (2017) PhotoGate microscopy to track single molecules in crowded environments. Nat Commun 8:13978|
|Dagdas, Yavuz S; Chen, Janice S; Sternberg, Samuel H et al. (2017) A conformational checkpoint between DNA binding and cleavage by CRISPR-Cas9. Sci Adv 3:eaao0027|
|Can, Sinan; Yildiz, Ahmet (2017) Measurement of Force-Dependent Release Rates of Cytoskeletal Motors. Methods Mol Biol 1486:469-481|
|Belyy, V; Yildiz, A (2017) Studying the Mechanochemistry of Processive Cytoskeletal Motors With an Optical Trap. Methods Enzymol 582:31-54|
|Chien, Alexander; Shih, Sheng Min; Bower, Raqual et al. (2017) Dynamics of the IFT machinery at the ciliary tip. Elife 6:|
|Chen, Janice S; Dagdas, Yavuz S; Kleinstiver, Benjamin P et al. (2017) Enhanced proofreading governs CRISPR-Cas9 targeting accuracy. Nature 550:407-410|
|Wichner, Sara M; Mann, Victor R; Powers, Alexander S et al. (2017) Covalent Protein Labeling and Improved Single-Molecule Optical Properties of Aqueous CdSe/CdS Quantum Dots. ACS Nano 11:6773-6781|
|Qin, Peiwu; Parlak, Mahmut; Kuscu, Cem et al. (2017) Live cell imaging of low- and non-repetitive chromosome loci using CRISPR-Cas9. Nat Commun 8:14725|
Showing the most recent 10 out of 26 publications