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2. The Antiparallel Coiled-Coil Domain Allows Multiple Forward Step Sizes of Myosin X

Author

Nguyen, Quang Quan, Zhou, Yangbo, Cheng, Man Sze, Qin, Xianan, Cheng, Harry Chun Man, Liu, Xiaoyan, Sweeney, H. Lee, Park, Hyo Keun, Nguyen, Quang Quan, Zhou, Yangbo, Cheng, Man Sze, Qin, Xianan, Cheng, Harry Chun Man, Liu, Xiaoyan, Sweeney, H. Lee, and Park, Hyo Keun

Abstract

Myosin X forms an antiparallel dimer and moves processively on actin bundles. How the antiparallel dimer affects the stepping mechanism of myosin X remains elusive. Here, we generated several chimeras using domains of myosin V and X and performed single-molecule motility assays. We found that the chimera containing the motor domain from myosin V and the lever arm and antiparallel coiled-coil domain from myosin X has multiple forward step sizes and moves processively, similar to full-length myosin X. The chimera containing the motor domain and lever arm from myosin X and the parallel coiled-coil from myosin V takes steps of ∼40 nm at lower ATP concentrations but was nonprocessive at higher ATP concentrations. Furthermore, mutant myosin X with four mutations in the antiparallel coiled-coil domain failed to dimerize and was nonprocessive. These results imply that the antiparallel coiled-coil domain is necessary for multiple forward step sizes of myosin X.

Published
2023

4. Simultaneous tracking of two motor domains reveals near simultaneous steps and stutter steps of myosin 10 on actin filament bundles

Author

Qin, Xianan, Yoo, Hanna, Cheng, Harry Chun Man, Nguyen, Quang Quan, Li, Jing, Liu, Xiaoyan, Prunetti, Laurence, Chen, Xingxiang, Liu, Teng, Sweeney, H. Lee, Park, Hyo Keun, Qin, Xianan, Yoo, Hanna, Cheng, Harry Chun Man, Nguyen, Quang Quan, Li, Jing, Liu, Xiaoyan, Prunetti, Laurence, Chen, Xingxiang, Liu, Teng, Sweeney, H. Lee, and Park, Hyo Keun

Abstract

Myosin X (Myo10) has several unique design features including dimerization via an anti-parallel coiled coil and a long lever arm, which allow it to preferentially move on actin bundles. To understand the stepping behavior of single Myo10 on actin bundles, we labeled two heads of Myo10 dimers with different fluorophores. Unlike previously described for myosin V (Myo5) and VI (Myo6), which display alternating hand-over-hand stepping, Myo10 frequently took near simultaneous steps of both heads, and less frequently, 2–3 steps of one head before the other head stepped. We suggest that this behavior results from the unusual kinetic features of Myo10, in conjunction with the structural properties of the motor domain/lever arm, which will favor movement on actin bundles rather than on single filaments. © 2020 Elsevier Inc.

Published
2020

6. Satellite cell expansion is mediated by P-eIF2α-dependent Tacc3 translation.

Author

Fujita R, Jamet S, Lean G, Cheng HCM, Hébert S, Kleinman CL, and Crist C

Subjects
Animals, Cell Differentiation genetics, Cell Proliferation, Cell Self Renewal, Cells, Cultured, Down-Regulation genetics, Mice, Inbred C57BL, PAX7 Transcription Factor metabolism, Phosphorylation, Proteome metabolism, RNA, Messenger genetics, RNA, Messenger metabolism, Regeneration, Transcriptome genetics, Up-Regulation genetics, Mice, Eukaryotic Initiation Factor-2 metabolism, Fetal Proteins metabolism, Microtubule-Associated Proteins metabolism, Protein Biosynthesis, Satellite Cells, Skeletal Muscle cytology, Satellite Cells, Skeletal Muscle metabolism
Abstract

Translational control of gene expression is an important regulator of adult stem cell quiescence, activation and self-renewal. In skeletal muscle, quiescent satellite cells maintain low levels of protein synthesis, mediated in part through the phosphorylation of eIF2α (P-eIF2α). Pharmacological inhibition of the eIF2α phosphatase with the small molecule sal003 maintains P-eIF2α and permits the expansion of satellite cells ex vivo Paradoxically, P-eIF2α also increases the translation of specific mRNAs, which is mediated by P-eIF2α-dependent read-through of inhibitory upstream open reading frames (uORFs). Here, we ask whether P-eIF2α-dependent mRNA translation enables expansion of satellite cells. Using transcriptomic and proteomic analyses, we show a number of genes associated with the assembly of the spindle pole to be upregulated at the level of protein, without corresponding change in mRNA levels, in satellite cells expanded in the presence of sal003. We show that uORFs in the 5' UTR of mRNA for the mitotic spindle stability gene Tacc3 direct P-eIF2α-dependent translation. Satellite cells deficient for TACC3 exhibit defects in expansion, self-renewal and regeneration of skeletal muscle., Competing Interests: Competing interestsThe authors declare no competing or financial interests., (© 2021. Published by The Company of Biologists Ltd.)

Published
2021
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