1
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Behbehani R, Johnson C, Holmes AJ, Gratian MJ, Mulvihill DP, Buss F. The two C. elegans class VI myosins, SPE-15/HUM-3 and HUM-8, share similar motor properties, but have distinct developmental and tissue expression patterns. Front Physiol 2024; 15:1368054. [PMID: 38660538 PMCID: PMC11040104 DOI: 10.3389/fphys.2024.1368054] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2024] [Accepted: 03/22/2024] [Indexed: 04/26/2024] Open
Abstract
Myosins of class VI move toward the minus-end of actin filaments and play vital roles in cellular processes such as endocytosis, autophagy, protein secretion, and the regulation of actin filament dynamics. In contrast to the majority of metazoan organisms examined to date which contain a single MYO6 gene, C. elegans, possesses two MYO6 homologues, SPE-15/HUM-3 and HUM-8. Through a combination of in vitro biochemical/biophysical analysis and cellular assays, we confirmed that both SPE-15/HUM-3 and HUM-8 exhibit reverse directionality, velocities, and ATPase activity similar to human MYO6. Our characterization also revealed that unlike SPE-15/HUM-3, HUM-8 is expressed as two distinct splice isoforms, one with an additional unique 14 amino acid insert in the cargo-binding domain. While lipid and adaptor binding sites are conserved in SPE-15/HUM-3 and HUM-8, this conservation does not enable recruitment to endosomes in mammalian cells. Finally, we performed super-resolution confocal imaging on transgenic worms expressing either mNeonGreen SPE-15/HUM-3 or wrmScarlet HUM-8. Our results show a clear distinction in tissue distribution between SPE-15/HUM-3 and HUM-8. While SPE-15/HUM-3 exhibited specific expression in the gonads and neuronal tissue in the head, HUM-8 was exclusively localized in the intestinal epithelium. Overall, these findings align with the established tissue distributions and localizations of human MYO6.
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Affiliation(s)
- Ranya Behbehani
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom
| | - Chloe Johnson
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom
| | - Alexander J. Holmes
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom
| | - Matthew J. Gratian
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom
| | | | - Folma Buss
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom
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2
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dos Santos Á, Fili N, Hari-Gupta Y, Gough RE, Wang L, Martin-Fernandez M, Aaron J, Wait E, Chew TL, Toseland CP. Binding partners regulate unfolding of myosin VI to activate the molecular motor. Biochem J 2022; 479:1409-1428. [PMID: 35722941 PMCID: PMC9342898 DOI: 10.1042/bcj20220025] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Revised: 06/15/2022] [Accepted: 06/20/2022] [Indexed: 11/22/2022]
Abstract
Myosin VI is the only minus-end actin motor and it is coupled to various cellular processes ranging from endocytosis to transcription. This multi-potent nature is achieved through alternative isoform splicing and interactions with a network of binding partners. There is a complex interplay between isoforms and binding partners to regulate myosin VI. Here, we have compared the regulation of two myosin VI splice isoforms by two different binding partners. By combining biochemical and single-molecule approaches, we propose that myosin VI regulation follows a generic mechanism, independently of the spliced isoform and the binding partner involved. We describe how myosin VI adopts an autoinhibited backfolded state which is released by binding partners. This unfolding activates the motor, enhances actin binding and can subsequently trigger dimerization. We have further expanded our study by using single-molecule imaging to investigate the impact of binding partners upon myosin VI molecular organization and dynamics.
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Affiliation(s)
- Ália dos Santos
- Department of Oncology and Metabolism, University of Sheffield, Sheffield S10 2RX, U.K
| | - Natalia Fili
- Department of Oncology and Metabolism, University of Sheffield, Sheffield S10 2RX, U.K
| | - Yukti Hari-Gupta
- School of Biosciences, University of Kent, Canterbury CT2 7NJ, U.K
| | - Rosemarie E. Gough
- Department of Oncology and Metabolism, University of Sheffield, Sheffield S10 2RX, U.K
| | - Lin Wang
- Central Laser Facility, Research Complex at Harwell, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell, Didcot, Oxford OX11 0QX, U.K
| | - Marisa Martin-Fernandez
- Central Laser Facility, Research Complex at Harwell, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell, Didcot, Oxford OX11 0QX, U.K
| | - Jesse Aaron
- Advanced Imaging Center, HHMI Janelia Research Campus, Ashburn, U.S.A
| | - Eric Wait
- Advanced Imaging Center, HHMI Janelia Research Campus, Ashburn, U.S.A
| | - Teng-Leong Chew
- Advanced Imaging Center, HHMI Janelia Research Campus, Ashburn, U.S.A
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3
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Zhu W, Duan Y, Chen J, Merzendorfer H, Zou X, Yang Q. SERCA interacts with chitin synthase and participates in cuticular chitin biogenesis in Drosophila. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2022; 145:103783. [PMID: 35525402 DOI: 10.1016/j.ibmb.2022.103783] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Revised: 03/30/2022] [Accepted: 04/29/2022] [Indexed: 06/14/2023]
Abstract
The biogenesis of chitin, a major structural polysaccharide found in the cuticle and peritrophic matrix, is crucial for insect growth and development. Chitin synthase, a membrane-integral β-glycosyltransferase, has been identified as the core of the chitin biogenesis machinery. However, a yet unknown number of auxiliary proteins appear to assist in chitin biosynthesis, whose precise function remains elusive. Here, we identified a sarco/endoplasmic reticulum Ca2+-ATPase (SERCA), in the fruit fly Drosophila melanogaster, as a chitin biogenesis-associated protein. The physical interaction between DmSERCA and epidermal chitin synthase (Krotzkopf verkehrt, Kkv) was demonstrated and analyzed using split-ubiquitin membrane yeast two-hybrid, bimolecular fluorescent complementation, pull-down, and immunoprecipitation assays. The interaction involves N-terminal regions (aa 48-81 and aa 247-33) and C-terminal regions (aa 743-783 and aa 824-859) of DmSERCA and two N-terminal regions (aa 121-179 and aa 369-539) of Kkv, all of which are predicted be transmembrane helices. While tissue-specific knock-down of DmSERCA in the epidermis caused larval and pupal lethality, the knock-down of DmSERCA in wings resulted in smaller and crinkled wings, a significant decrease in chitin deposition, and the loss of chitin lamellar structure. Although DmSERCA is well-known for its role in muscular contraction, this study reveals a novel role in chitin synthesis, contributing to our knowledge on the machinery of chitin biogenesis.
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Affiliation(s)
- Weixing Zhu
- School of Bioengineering, Dalian University of Technology, No. 2, Linggong Road, Dalian, 116024, China
| | - Yanwei Duan
- School of Bioengineering, Dalian University of Technology, No. 2, Linggong Road, Dalian, 116024, China
| | - Jiqiang Chen
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, No. 2 West Yuanmingyuan Road, Beijing, 100193, China
| | - Hans Merzendorfer
- Institute of Biology, University of Siegen, Adolf-Reichwein-Strasse 2, Siegen, 57068, Germany
| | - Xu Zou
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, No. 2 West Yuanmingyuan Road, Beijing, 100193, China
| | - Qing Yang
- School of Bioengineering, Dalian University of Technology, No. 2, Linggong Road, Dalian, 116024, China; State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, No. 2 West Yuanmingyuan Road, Beijing, 100193, China; Shenzhen Branch, Guangdong Laboratory of Lingnan Modern Agriculture, Genome Analysis Laboratory of the Ministry of Agriculture and Rural Affairs, Agricultural Genomics Institute at Shenzhen, Chinese Academy of Agricultural Sciences, No 7 Pengfei Road, Shenzhen, 518120, China.
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4
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Duan Y, Zhu W, Zhao X, Merzendorfer H, Chen J, Zou X, Yang Q. Choline transporter-like protein 2 interacts with chitin synthase 1 and is involved in insect cuticle development. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2022; 141:103718. [PMID: 34982980 DOI: 10.1016/j.ibmb.2021.103718] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Revised: 12/29/2021] [Accepted: 12/29/2021] [Indexed: 06/14/2023]
Abstract
Chitin is an aminopolysaccharide present in insects as a major structural component of the cuticle. However, current knowledge on the chitin biosynthetic machinery, especially its constituents and mechanism, is limited. Using three independent binding assays, including co-immunoprecipitation, split-ubiquitin membrane yeast two-hybrid assay, and pull-down assay, we demonstrate that choline transporter-like protein 2 (Ctl2) interacts with krotzkopf verkehrt (kkv) in Drosophila melanogaster. The global knockdown of Ctl2 by RNA interference (RNAi) induced lethality at the larval stage. Tissue-specific RNAi to silence Ctl2 in the tracheal system and in the epidermis of the flies resulted in lethality at the first larval instar. The knockdown of Ctl2 in wings led to shrunken wings containing accumulated fluid. Calcofluor White staining demonstrated reduced chitin content in the first longitudinal vein of Ctl2 knockdown wings. The pro-cuticle, which was thinner compared to wildtype, exhibited a reduced number of chitin laminar layers. Phylogenetic analyses revealed orthologues of Ctl2 in different insect orders with highly conserved domains. Our findings provide new insights into cuticle formation, wherein Ctl2 plays an important role as a chitin-synthase interacting protein.
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Affiliation(s)
- Yanwei Duan
- School of Bioengineering, Dalian University of Technology, No. 2, Linggong Road, Dalian, 116024, China
| | - Weixing Zhu
- School of Bioengineering, Dalian University of Technology, No. 2, Linggong Road, Dalian, 116024, China
| | - Xiaoming Zhao
- Institute of Applied Biology, Shanxi University, Taiyuan, Shanxi, 030006, China
| | - Hans Merzendorfer
- Institute of Biology, University of Siegen, Adolf-Reichwein-Strasse 2, Siegen, 57068, Germany
| | - Jiqiang Chen
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, No. 2 West Yuanmingyuan Road, Beijing, 100193, China
| | - Xu Zou
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, No. 2 West Yuanmingyuan Road, Beijing, 100193, China
| | - Qing Yang
- School of Bioengineering, Dalian University of Technology, No. 2, Linggong Road, Dalian, 116024, China; State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, No. 2 West Yuanmingyuan Road, Beijing, 100193, China; Shenzhen Branch, Guangdong Laboratory of Lingnan Modern Agriculture, Genome Analysis Laboratory of the Ministry of Agriculture and Rural Affairs, Agricultural Genomics Institute at Shenzhen, Chinese Academy of Agricultural Sciences, No 7 Pengfei Road, Shenzhen, 518120, China.
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5
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Kneussel M, Sánchez-Rodríguez N, Mischak M, Heisler FF. Dynein and muskelin control myosin VI delivery towards the neuronal nucleus. iScience 2021; 24:102416. [PMID: 33997696 PMCID: PMC8099778 DOI: 10.1016/j.isci.2021.102416] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Revised: 02/15/2021] [Accepted: 04/07/2021] [Indexed: 11/30/2022] Open
Abstract
Protein transport toward the nucleus is important for translating molecular signals into gene expression changes. Interestingly, the unconventional motor protein myosin VI regulates RNA polymerase II-dependent gene transcription. Whether actin-filament-dependent myosins are actively transported to nuclear compartments remains unknown. Here, we report that neurons also contain myosin VI inside their nucleus. Notably, nuclear appearance of this actin-dependent motor depends on functional cytoplasmic dynein, a minus end-directed microtubule motor. We find that the trafficking factor muskelin assists in the formation of dynein-myosin VI interactions and further localizes to nuclear foci, enriched in the myosin. Impairment of dynein, but not myosin VI function, reduces nuclear muskelin levels. In turn, muskelin represents a critical determinant in regulating myosin VI nuclear targeting. Our data reveal that minus end-directed microtubule transport determines myosin VI subcellular localization. They suggest a pathway of cytoplasm-to-nucleus trafficking that requires muskelin and is based on dynein-myosin cross talk.
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Affiliation(s)
- Matthias Kneussel
- Department of Molecular Neurogenetics, Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, Falkenried 94, 20251 Hamburg, Germany
| | - Noelia Sánchez-Rodríguez
- Department of Molecular Neurogenetics, Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, Falkenried 94, 20251 Hamburg, Germany
| | - Michaela Mischak
- Department of Molecular Neurogenetics, Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, Falkenried 94, 20251 Hamburg, Germany
| | - Frank F. Heisler
- Department of Molecular Neurogenetics, Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, Falkenried 94, 20251 Hamburg, Germany
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6
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Myomics: myosin VI structural and functional plasticity. Curr Opin Struct Biol 2020; 67:33-40. [PMID: 33053464 DOI: 10.1016/j.sbi.2020.09.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Revised: 09/02/2020] [Accepted: 09/07/2020] [Indexed: 11/21/2022]
Abstract
Myosin VI is a minus end-directed actin motor protein that fulfils several roles in the cell. The interaction of myosin VI with its cellular cargoes is dictated by the presence of binding domains at the C-terminus of the protein. In this review, we describe how alternative splicing and structural and conformational changes modulate the plasticity of the myosin VI interactome. Recent findings highlight how the various partners can cooperate or compete for binding to allow a precise temporal and spatial regulation of myosin VI recruitment to different cellular compartments, where its motor or anchor function is needed.
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7
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O'Loughlin T, Kendrick-Jones J, Buss F. Approaches to Identify and Characterise MYO6-Cargo Interactions. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2020; 1239:355-380. [PMID: 32451866 DOI: 10.1007/978-3-030-38062-5_15] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Given the prevalence and importance of the actin cytoskeleton and the host of associated myosin motors, it comes as no surprise to find that they are linked to a plethora of cellular functions and pathologies. Although our understanding of the biophysical properties of myosin motors has been aided by the high levels of conservation in their motor domains and the extensive work on myosin in skeletal muscle contraction, our understanding of how the nonmuscle myosins participate in such a wide variety of cellular processes is less clear. It is now well established that the highly variable myosin tails are responsible for targeting these myosins to distinct cellular sites for specific functions, and although a number of adaptor proteins have been identified, our current understanding of the cellular processes involved is rather limited. Furthermore, as more adaptor proteins, cargoes and complexes are identified, the importance of elucidating the regulatory mechanisms involved is essential. Ca2+, and now phosphorylation and ubiquitination, are emerging as important regulators of cargo binding, and it is likely that other post-translational modifications are also involved. In the case of myosin VI (MYO6), a number of immediate binding partners have been identified using traditional approaches such as yeast two-hybrid screens and affinity-based pull-downs. However, these methods have only been successful in identifying the cargo adaptors, but not the cargoes themselves, which may often comprise multi-protein complexes. Furthermore, motor-adaptor-cargo interactions are dynamic by nature and often weak, transient and highly regulated and therefore difficult to capture using traditional affinity-based methods. In this chapter we will discuss the various approaches including functional proteomics that have been used to uncover and characterise novel MYO6-associated proteins and complexes and how this work contributes to a fuller understanding of the targeting and function(s) of this unique myosin motor.
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Affiliation(s)
- Thomas O'Loughlin
- Cambridge Institute for Medical Research, University of Cambridge, The Keith Peters Building, Cambridge, UK
| | | | - Folma Buss
- Cambridge Institute for Medical Research, University of Cambridge, The Keith Peters Building, Cambridge, UK.
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8
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de Jonge JJ, Batters C, O'Loughlin T, Arden SD, Buss F. The MYO6 interactome: selective motor-cargo complexes for diverse cellular processes. FEBS Lett 2019; 593:1494-1507. [PMID: 31206648 DOI: 10.1002/1873-3468.13486] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2019] [Revised: 06/07/2019] [Accepted: 06/10/2019] [Indexed: 12/16/2022]
Abstract
Myosins of class VI (MYO6) are unique actin-based motor proteins that move cargo towards the minus ends of actin filaments. As the sole myosin with this directionality, it is critically important in a number of biological processes. Indeed, loss or overexpression of MYO6 in humans is linked to a variety of pathologies including deafness, cardiomyopathy, neurodegenerative diseases as well as cancer. This myosin interacts with a wide variety of direct binding partners such as for example the selective autophagy receptors optineurin, TAX1BP1 and NDP52 and also Dab2, GIPC, TOM1 and LMTK2, which mediate distinct functions of different MYO6 isoforms along the endocytic pathway. Functional proteomics has recently been used to identify the wider MYO6 interactome including several large functionally distinct multi-protein complexes, which highlight the importance of this myosin in regulating the actin and septin cytoskeleton. Interestingly, adaptor-binding not only triggers cargo attachment, but also controls the inactive folded conformation and dimerisation of MYO6. Thus, the C-terminal tail domain mediates cargo recognition and binding, but is also crucial for modulating motor activity and regulating cytoskeletal track dynamics.
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Affiliation(s)
| | | | - Thomas O'Loughlin
- Cambridge Institute for Medical Research, University of Cambridge, UK
| | - Susan D Arden
- Cambridge Institute for Medical Research, University of Cambridge, UK
| | - Folma Buss
- Cambridge Institute for Medical Research, University of Cambridge, UK
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9
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Luo J, Shen P, Chen J. A modular toolset of phiC31-based fluorescent protein tagging vectors for Drosophila. Fly (Austin) 2019; 13:29-41. [PMID: 30885036 DOI: 10.1080/19336934.2019.1595999] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
Abstract
The Drosophila transgenic technology and fluorescent protein fusions are powerful tools to analyze protein expression patterns, subcellular localization and protein dynamics. Recently, the Drosophila transgenic technology has been improved by the highly efficient phiC31 site-specific integration system. Many new and improved fluorescent proteins with desirable advantages have been developed. However, the phiC31 system and the newly developed fluorescent proteins have not been systematically applied in Drosophila transgenic vectors. Here, we have constructed a modular toolset of C-terminal fluorescent protein fusion vectors based on phiC31 site-specific integration system for the generation of transgenic Drosophila lines. These cloning vectors contain a variety of fluorescent tags, including blue, cyan, green or red fluorescent proteins, photoactivatable or photoswitchable fluorescent proteins, fluorescent timers, photosensitizers and bimolecular fluorescence complementation tags. These vectors provide a range of transcriptional regulation options including UAST, UASP, UASC, LexAop, QUAS, Ubi, αTub67C and αTub84B promoters, and two screening marker options including white and vermilion gene. The vectors have been tested in vivo and can produce fluorescent chimeric proteins that are functional.
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Affiliation(s)
- Jun Luo
- State Key Laboratory of Pharmaceutical Biotechnology and MOE Key Laboratory of Model Animals for Disease Study, Model Animal Research Center, Nanjing University, Nanjing, China
| | - Pingping Shen
- State Key Laboratory of Pharmaceutical Biotechnology and MOE Key Laboratory of Model Animals for Disease Study, Model Animal Research Center, Nanjing University, Nanjing, China.,State Key Laboratory of Pharmaceutical Biotechnology, School of life Sciences, Nanjing University, Nanjing, China
| | - Jiong Chen
- State Key Laboratory of Pharmaceutical Biotechnology and MOE Key Laboratory of Model Animals for Disease Study, Model Animal Research Center, Nanjing University, Nanjing, China
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10
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Ryan TA, Tumbarello DA. Optineurin: A Coordinator of Membrane-Associated Cargo Trafficking and Autophagy. Front Immunol 2018; 9:1024. [PMID: 29867991 PMCID: PMC5962687 DOI: 10.3389/fimmu.2018.01024] [Citation(s) in RCA: 77] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Accepted: 04/24/2018] [Indexed: 12/13/2022] Open
Abstract
Optineurin is a multifunctional adaptor protein intimately involved in various vesicular trafficking pathways. Through interactions with an array of proteins, such as myosin VI, huntingtin, Rab8, and Tank-binding kinase 1, as well as via its oligomerisation, optineurin has the ability to act as an adaptor, scaffold, or signal regulator to coordinate many cellular processes associated with the trafficking of membrane-delivered cargo. Due to its diverse interactions and its distinct functions, optineurin is an essential component in a number of homeostatic pathways, such as protein trafficking and organelle maintenance. Through the binding of polyubiquitinated cargoes via its ubiquitin-binding domain, optineurin also serves as a selective autophagic receptor for the removal of a wide range of substrates. Alternatively, it can act in an ubiquitin-independent manner to mediate the clearance of protein aggregates. Regarding its disease associations, mutations in the optineurin gene are associated with glaucoma and have more recently been found to correlate with Paget’s disease of bone and amyotrophic lateral sclerosis (ALS). Indeed, ALS-associated mutations in optineurin result in defects in neuronal vesicular localisation, autophagosome–lysosome fusion, and secretory pathway function. More recent molecular and functional analysis has shown that it also plays a role in mitophagy, thus linking it to a number of other neurodegenerative conditions, such as Parkinson’s. Here, we review the role of optineurin in intracellular membrane trafficking, with a focus on autophagy, and describe how upstream signalling cascades are critical to its regulation. Current data and contradicting reports would suggest that optineurin is an important and selective autophagy receptor under specific conditions, whereby interplay, synergy, and functional redundancy with other receptors occurs. We will also discuss how dysfunction in optineurin-mediated pathways may lead to perturbation of critical cellular processes, which can drive the pathologies of number of diseases. Therefore, further understanding of optineurin function, its target specificity, and its mechanism of action will be critical in fully delineating its role in human disease.
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Affiliation(s)
- Thomas A Ryan
- Biological Sciences, University of Southampton, Southampton, United Kingdom
| | - David A Tumbarello
- Biological Sciences, University of Southampton, Southampton, United Kingdom
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11
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He F, Wollscheid HP, Nowicka U, Biancospino M, Valentini E, Ehlinger A, Acconcia F, Magistrati E, Polo S, Walters KJ. Myosin VI Contains a Compact Structural Motif that Binds to Ubiquitin Chains. Cell Rep 2016; 14:2683-94. [PMID: 26971995 DOI: 10.1016/j.celrep.2016.01.079] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2015] [Revised: 11/24/2015] [Accepted: 01/27/2016] [Indexed: 12/13/2022] Open
Abstract
Myosin VI is critical for cargo trafficking and sorting during early endocytosis and autophagosome maturation, and abnormalities in these processes are linked to cancers, neurodegeneration, deafness, and hypertropic cardiomyopathy. We identify a structured domain in myosin VI, myosin VI ubiquitin-binding domain (MyUb), that binds to ubiquitin chains, especially those linked via K63, K11, and K29. Herein, we solve the solution structure of MyUb and MyUb:K63-linked diubiquitin. MyUb folds as a compact helix-turn-helix-like motif and nestles between the ubiquitins of K63-linked diubiquitin, interacting with distinct surfaces of each. A nine-amino-acid extension at the C-terminal helix (Helix2) of MyUb is required for myosin VI interaction with endocytic and autophagic adaptors. Structure-guided mutations revealed that a functional MyUb is necessary for optineurin interaction. In addition, we found that an isoform-specific helix restricts MyUb binding to ubiquitin chains. This work provides fundamental insights into myosin VI interaction with ubiquitinated cargo and functional adaptors.
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Affiliation(s)
- Fahu He
- Protein Processing Section, Structural Biophysics Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702, USA
| | - Hans-Peter Wollscheid
- IFOM, Fondazione Istituto FIRC di Oncologia Molecolare, Via Adamello 16, 20139 Milano, Italy
| | - Urszula Nowicka
- Protein Processing Section, Structural Biophysics Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702, USA
| | - Matteo Biancospino
- IFOM, Fondazione Istituto FIRC di Oncologia Molecolare, Via Adamello 16, 20139 Milano, Italy
| | - Eleonora Valentini
- IFOM, Fondazione Istituto FIRC di Oncologia Molecolare, Via Adamello 16, 20139 Milano, Italy
| | - Aaron Ehlinger
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA
| | - Filippo Acconcia
- IFOM, Fondazione Istituto FIRC di Oncologia Molecolare, Via Adamello 16, 20139 Milano, Italy
| | - Elisa Magistrati
- IFOM, Fondazione Istituto FIRC di Oncologia Molecolare, Via Adamello 16, 20139 Milano, Italy
| | - Simona Polo
- IFOM, Fondazione Istituto FIRC di Oncologia Molecolare, Via Adamello 16, 20139 Milano, Italy; DIPO, Dipartimento di Oncologia ed Emato-oncologia, Università degli Studi di Milano, Via di Rudinì 8, 20122 Milan, Italy.
| | - Kylie J Walters
- Protein Processing Section, Structural Biophysics Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702, USA.
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12
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Manor U, Bartholomew S, Golani G, Christenson E, Kozlov M, Higgs H, Spudich J, Lippincott-Schwartz J. A mitochondria-anchored isoform of the actin-nucleating spire protein regulates mitochondrial division. eLife 2015; 4:e08828. [PMID: 26305500 PMCID: PMC4574297 DOI: 10.7554/elife.08828] [Citation(s) in RCA: 221] [Impact Index Per Article: 24.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2015] [Accepted: 08/24/2015] [Indexed: 12/18/2022] Open
Abstract
Mitochondrial division, essential for survival in mammals, is enhanced by an inter-organellar process involving ER tubules encircling and constricting mitochondria. The force for constriction is thought to involve actin polymerization by the ER-anchored isoform of the formin protein inverted formin 2 (INF2). Unknown is the mechanism triggering INF2-mediated actin polymerization at ER-mitochondria intersections. We show that a novel isoform of the formin-binding, actin-nucleating protein Spire, Spire1C, localizes to mitochondria and directly links mitochondria to the actin cytoskeleton and the ER. Spire1C binds INF2 and promotes actin assembly on mitochondrial surfaces. Disrupting either Spire1C actin- or formin-binding activities reduces mitochondrial constriction and division. We propose Spire1C cooperates with INF2 to regulate actin assembly at ER-mitochondrial contacts. Simulations support this model's feasibility and demonstrate polymerizing actin filaments can induce mitochondrial constriction. Thus, Spire1C is optimally positioned to serve as a molecular hub that links mitochondria to actin and the ER for regulation of mitochondrial division.
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Affiliation(s)
- Uri Manor
- Cell Biology and Metabolism Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, United States
| | - Sadie Bartholomew
- Department of Biochemistry, Stanford University School of Medicine, Stanford, United States
| | - Gonen Golani
- Department of Physiology and Pharmacology, Tel Aviv University, Tel Aviv, Israel
| | - Eric Christenson
- Unit on Structural and Chemical Biology of Membrane Proteins, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, United States
| | - Michael Kozlov
- Department of Physiology and Pharmacology, Tel Aviv University, Tel Aviv, Israel
| | - Henry Higgs
- Department of Biochemistry, Geisel School of Medicine, Hanover, United States
| | - James Spudich
- Department of Biochemistry, Stanford University School of Medicine, Stanford, United States
| | - Jennifer Lippincott-Schwartz
- Cell Biology and Metabolism Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, United States
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Beaven R, Dzhindzhev NS, Qu Y, Hahn I, Dajas-Bailador F, Ohkura H, Prokop A. Drosophila CLIP-190 and mammalian CLIP-170 display reduced microtubule plus end association in the nervous system. Mol Biol Cell 2015; 26:1491-508. [PMID: 25694447 PMCID: PMC4395129 DOI: 10.1091/mbc.e14-06-1083] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2014] [Accepted: 02/10/2015] [Indexed: 11/11/2022] Open
Abstract
Usually, CLIPs promote microtubule growth by binding their plus ends. However, in neurons, mouse CLIP-170 and fly CLIP-190 are weak end binders, instead forming actin/myosin VI–dependent patches in the center of growth cones. Total CLIP-190 loss, even together with four other plus end binders, reveals no role in neuronal MT regulation. Axons act like cables, electrically wiring the nervous system. Polar bundles of microtubules (MTs) form their backbones and drive their growth. Plus end–tracking proteins (+TIPs) regulate MT growth dynamics and directionality at their plus ends. However, current knowledge about +TIP functions, mostly derived from work in vitro and in nonneuronal cells, may not necessarily apply to the very different context of axonal MTs. For example, the CLIP family of +TIPs are known MT polymerization promoters in nonneuronal cells. However, we show here that neither Drosophila CLIP-190 nor mammalian CLIP-170 is a prominent MT plus end tracker in neurons, which we propose is due to low plus end affinity of the CAP-Gly domain–containing N-terminus and intramolecular inhibition through the C-terminus. Instead, both CLIP-190 and CLIP-170 form F-actin–dependent patches in growth cones, mediated by binding of the coiled-coil domain to myosin-VI. Because our loss-of-function analyses in vivo and in culture failed to reveal axonal roles for CLIP-190, even in double-mutant combinations with four other +TIPs, we propose that CLIP-190 and -170 are not essential axon extension regulators. Our findings demonstrate that +TIP functions known from nonneuronal cells do not necessarily apply to the regulation of the very distinct MT networks in axons.
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Affiliation(s)
- Robin Beaven
- Faculty of Life Sciences, The University of Manchester, Manchester M13 9PT, United Kingdom
| | - Nikola S Dzhindzhev
- Wellcome Trust Centre for Cell Biology, Institute of Cell Biology, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JR, United Kingdom
| | - Yue Qu
- Faculty of Life Sciences, The University of Manchester, Manchester M13 9PT, United Kingdom
| | - Ines Hahn
- Faculty of Life Sciences, The University of Manchester, Manchester M13 9PT, United Kingdom
| | | | - Hiroyuki Ohkura
- Wellcome Trust Centre for Cell Biology, Institute of Cell Biology, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JR, United Kingdom
| | - Andreas Prokop
- Faculty of Life Sciences, The University of Manchester, Manchester M13 9PT, United Kingdom
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14
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Kisiel M, McKenzie K, Stewart B. Localization and mobility of synaptic vesicles in Myosin VI mutants of Drosophila. PLoS One 2014; 9:e102988. [PMID: 25062032 PMCID: PMC4111356 DOI: 10.1371/journal.pone.0102988] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2013] [Accepted: 06/26/2014] [Indexed: 11/25/2022] Open
Abstract
Background At the Drosophila neuromuscular junction (NMJ), synaptic vesicles are mobile; however, the mechanisms that regulate vesicle traffic at the nerve terminal are not fully understood. Myosin VI has been shown to be important for proper synaptic physiology and morphology at the NMJ, likely by functioning as a vesicle tether. Here we investigate vesicle dynamics in Myosin VI mutants of Drosophila. Results In Drosophila, Myosin VI is encoded by the gene, jaguar (jar). To visualize active vesicle cycling we used FM dye loading and compared loss of function alleles of jar with controls. These studies revealed a differential distribution of vesicles at the jar mutant nerve terminal, with the newly endocytosed vesicles observed throughout the mutant boutons in contrast to the peripheral localization visualized at control NMJs. This finding is consistent with a role for Myosin VI in restraining vesicle mobility at the synapse to ensure proper localization. To further investigate regulation of vesicle dynamics by Myosin VI, FRAP analysis was used to analyze movement of GFP-labeled synaptic vesicles within individual boutons. FRAP revealed that synaptic vesicles are moving more freely in the jar mutant boutons, indicated by changes in initial bleach depth and rapid recovery of fluorescence following photobleaching. Conclusion This data provides insights into the role for Myosin VI in mediating synaptic vesicle dynamics at the nerve terminal. We observed mislocalization of actively cycling vesicles and an apparent increase in vesicle mobility when Myosin VI levels are reduced. These observations support the notion that a major function of Myosin VI in the nerve terminal is tethering synaptic vesicles to proper sub-cellular location within the bouton.
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Affiliation(s)
- Marta Kisiel
- Department of Biology, University of Toronto Mississauga, Mississauga, Canada
| | - Kristopher McKenzie
- Department of Biology, University of Toronto Mississauga, Mississauga, Canada
| | - Bryan Stewart
- Department of Biology, University of Toronto Mississauga, Mississauga, Canada
- Department of Cell and Systems Biology, University of Toronto, Toronto, Canada
- * E-mail:
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Tumbarello DA, Kendrick-Jones J, Buss F. Myosin VI and its cargo adaptors - linking endocytosis and autophagy. J Cell Sci 2013; 126:2561-70. [PMID: 23781020 DOI: 10.1242/jcs.095554] [Citation(s) in RCA: 94] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The coordinated trafficking and tethering of membrane cargo within cells relies on the function of distinct cytoskeletal motors that are targeted to specific subcellular compartments through interactions with protein adaptors and phospholipids. The unique actin motor myosin VI functions at distinct steps during clathrin-mediated endocytosis and the early endocytic pathway - both of which are involved in cargo trafficking and sorting - through interactions with Dab2, GIPC, Tom1 and LMTK2. This multifunctional ability of myosin VI can be attributed to its cargo-binding tail region that contains two protein-protein interaction interfaces, a ubiquitin-binding motif and a phospholipid binding domain. In addition, myosin VI has been shown to be a regulator of the autophagy pathway, because of its ability to link the endocytic and autophagic pathways through interactions with the ESCRT-0 protein Tom1 and the autophagy adaptor proteins T6BP, NDP52 and optineurin. This function has been attributed to facilitating autophagosome maturation and subsequent fusion with the lysosome. Therefore, in this Commentary, we discuss the relationship between myosin VI and the different myosin VI adaptor proteins, particularly with regards to the spatial and temporal regulation that is required for the sorting of cargo at the early endosome, and their impact on autophagy.
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Affiliation(s)
- David A Tumbarello
- Cambridge Institute for Medical Research, University of Cambridge, Hills Road, Cambridge CB2 0XY, UK
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Affiliation(s)
- M Amanda Hartman
- Department of Biochemistry, Stanford University, Stanford, CA 94305, USA
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17
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Myosin VI in skeletal muscle: its localization in the sarcoplasmic reticulum, neuromuscular junction and muscle nuclei. Histochem Cell Biol 2012; 139:873-85. [PMID: 23275125 PMCID: PMC3656228 DOI: 10.1007/s00418-012-1070-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/10/2012] [Indexed: 01/19/2023]
Abstract
Myosin VI (MVI) is a unique unconventional motor moving backwards on actin filaments. In non-muscle cells, it is involved in cell migration, endocytosis and intracellular trafficking, actin cytoskeleton dynamics, and possibly in gene transcription. An important role for MVI in striated muscle functioning was suggested in a report showing that a point mutation (H236R) within the MVI gene was associated with cardiomyopathy (Mohiddin et al., J Med Genet 41:309–314, 2004). Here, we have addressed MVI function in striated muscle by examining its expression and distribution in rat hindlimb skeletal muscle. We found that MVI was present predominantly at the muscle fiber periphery, and it was also localized within muscle nuclei. Analysis of both the hindlimb and cardiac muscle longitudinal sections revealed ~3 μm striation pattern, corresponding to the sarcoplasmic reticulum. Moreover, MVI was detected in the sarcoplasmic reticulum fractions isolated from skeletal and cardiac muscle. The protein also localized to the postsynaptic region of the neuromuscular junction. In denervated muscle, the defined MVI distribution pattern was abolished and accompanied by significant increase in its amount in the muscle fibers. In addition, we have identified several novel potential MVI-binding partners, which seem to aid our observations that in striated muscle MVI could be involved in postsynaptic trafficking as well as in maintenance of and/or transport within the sarcoplasmic reticulum and non-sarcomeric cytoskeleton.
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Mu Y, Huang H, Liu S, Cai P, Gao Y. Molecular characterization and ligand binding specificity of the PDZ domain-containing protein GIPC3 from Schistosoma japonicum. Parasit Vectors 2012; 5:227. [PMID: 23050840 PMCID: PMC3504512 DOI: 10.1186/1756-3305-5-227] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2012] [Accepted: 10/05/2012] [Indexed: 01/09/2023] Open
Abstract
Background Schistosomiasis is a serious global health problem that afflicts more than 230 million people in 77 countries. Long-term mass treatments with the only available drug, praziquantel, have caused growing concerns about drug resistance. PSD-95/Dlg/ZO-1 (PDZ) domain-containing proteins are recognized as potential targets for the next generation of drug development. However, the PDZ domain-containing protein family in parasites has largely been unexplored. Methods We present the molecular characteristics of a PDZ domain-containing protein, GIPC3, from Schistosoma japonicum (SjGIPC3) according to bioinformatics analysis and experimental approaches. The ligand binding specificity of the PDZ domain of SjGIPC3 was confirmed by screening an arbitrary peptide library in yeast two-hybrid (Y2H) assays. The native ligand candidates were predicted by Tailfit software based on the C-terminal binding specificity, and further validated by Y2H assays. Results SjGIPC3 is a single PDZ domain-containing protein comprised of 328 amino acid residues. Structural prediction revealed that a conserved PDZ domain was presented in the middle region of the protein. Phylogenetic analysis revealed that SjGIPC3 and other trematode orthologues clustered into a well-defined cluster but were distinguishable from those of other phyla. Transcriptional analysis by quantitative RT-PCR revealed that the SjGIPC3 gene was relatively highly expressed in the stages within the host, especially in male adult worms. By using Y2H assays to screen an arbitrary peptide library, we confirmed the C-terminal binding specificity of the SjGIPC3-PDZ domain, which could be deduced as a consensus sequence, -[SDEC]-[STIL]-[HSNQDE]-[VIL]*. Furthermore, six proteins were predicted to be native ligand candidates of SjGIPC3 based on the C-terminal binding properties and other biological information; four of these were confirmed to be potential ligands using the Y2H system. Conclusions In this study, we first characterized a PDZ domain-containing protein GIPC3 in S. japonicum. The SjGIPC3-PDZ domain is able to bind both type I and II ligand C-terminal motifs. The identification of native ligand will help reveal the potential biological function of SjGIPC3. These data will facilitate the identification of novel drug targets against S. japonicum infections.
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Affiliation(s)
- Yi Mu
- National Key Laboratory of Medical Molecular Biology, Dept, of Physiology and Pathophysiology, School of Basic Medicine, Peking Union Medical College, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences, Beijing 100005, P,R, China
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19
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Zhang Y, Liao JC. Identifying Highly Conserved and Unique Structural Elements in Myosin VI. Cell Mol Bioeng 2012. [DOI: 10.1007/s12195-012-0254-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
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20
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Tumbarello DA, Waxse BJ, Arden SD, Bright NA, Kendrick-Jones J, Buss F. Autophagy receptors link myosin VI to autophagosomes to mediate Tom1-dependent autophagosome maturation and fusion with the lysosome. Nat Cell Biol 2012; 14:1024-35. [PMID: 23023224 PMCID: PMC3472162 DOI: 10.1038/ncb2589] [Citation(s) in RCA: 222] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2012] [Accepted: 08/23/2012] [Indexed: 02/06/2023]
Abstract
Autophagy targets pathogens, damaged organelles and protein aggregates for lysosomal degradation. These ubiquitylated cargoes are recognized by specific autophagy receptors, which recruit LC3-positive membranes to form autophagosomes. Subsequently, autophagosomes fuse with endosomes and lysosomes, thus facilitating degradation of their content; however, the machinery that targets and mediates fusion of these organelles with autophagosomes remains to be established. Here we demonstrate that myosin VI, in concert with its adaptor proteins NDP52, optineurin, T6BP and Tom1, plays a crucial role in autophagy. We identify Tom1 as a myosin VI binding partner on endosomes, and demonstrate that loss of myosin VI and Tom1 reduces autophagosomal delivery of endocytic cargo and causes a block in autophagosome-lysosome fusion. We propose that myosin VI delivers endosomal membranes containing Tom1 to autophagosomes by docking to NDP52, T6BP and optineurin, thereby promoting autophagosome maturation and thus driving fusion with lysosomes.
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Affiliation(s)
- David A. Tumbarello
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge, CB2 0XY, UK
| | - Bennett J. Waxse
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge, CB2 0XY, UK
| | - Susan D. Arden
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge, CB2 0XY, UK
| | - Nicholas A. Bright
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge, CB2 0XY, UK
| | | | - Folma Buss
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge, CB2 0XY, UK
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Structure of androcam supports specialized interactions with myosin VI. Proc Natl Acad Sci U S A 2012; 109:13290-5. [PMID: 22851764 DOI: 10.1073/pnas.1209730109] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Androcam replaces calmodulin as a tissue-specific myosin VI light chain on the actin cones that mediate D. melanogaster spermatid individualization. We show that the androcam structure and its binding to the myosin VI structural (Insert 2) and regulatory (IQ) light chain sites are distinct from those of calmodulin and provide a basis for specialized myosin VI function. The androcam N lobe noncanonically binds a single Ca(2+) and is locked in a "closed" conformation, causing androcam to contact the Insert 2 site with its C lobe only. Androcam replacing calmodulin at Insert 2 will increase myosin VI lever arm flexibility, which may favor the compact monomeric form of myosin VI that functions on the actin cones by facilitating the collapse of the C-terminal region onto the motor domain. The tethered androcam N lobe could stabilize the monomer through contacts with C-terminal portions of the motor or recruit other components to the actin cones. Androcam binds the IQ site at all calcium levels, constitutively mimicking a conformation adopted by calmodulin only at intermediate calcium levels. Thus, androcam replacing calmodulin at IQ will abolish a Ca(2+)-regulated, calmodulin-mediated myosin VI structural change. We propose that the N lobe prevents androcam from interfering with other calmodulin-mediated Ca(2+) signaling events. We discuss how gene duplication and mutations that selectively stabilize one of the many conformations available to calmodulin support the molecular evolution of structurally and functionally distinct calmodulin-like proteins.
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Llinas P, Pylypenko O, Isabet T, Mukherjea M, Sweeney HL, Houdusse AM. How myosin motors power cellular functions: an exciting journey from structure to function: based on a lecture delivered at the 34th FEBS Congress in Prague, Czech Republic, July 2009. FEBS J 2012; 279:551-62. [PMID: 22171985 PMCID: PMC3269445 DOI: 10.1111/j.1742-4658.2011.08449.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Molecular motors such as myosins are allosteric enzymes that power essential motility functions in the cell. Structural biology is an important tool for deciphering how these motors work. Myosins produce force upon the actin-driven conformational changes controlling the sequential release of the hydrolysis products of ATP (Pi followed by ADP). These conformational changes are amplified by a 'lever arm', which includes the region of the motor known as the converter and the adjacent elongated light chain binding region. Analysis of four structural states of the motor provides a detailed understanding of the rearrangements and pathways of communication in the motor that are necessary for detachment from the actin track and repriming of the motor. However, the important part of the cycle in which force is produced remains enigmatic and awaits new high-resolution structures. The value of a structural approach is particularly evident from clues provided by the structural states of the reverse myosin VI motor. Crystallographic structures have revealed that rearrangements within the converter subdomain occur, which explains why this myosin can produce a large stroke in the opposite direction to all other myosins, despite a very short lever arm. By providing a detailed understanding of the motor rearrangements, structural biology will continue to reveal essential information and help solve current enigma, such as how actin promotes force production, how motors are tuned for specific cellular roles or how motor/cargo interactions regulate the function of myosin in the cell.
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Affiliation(s)
- Paola Llinas
- Structural Motility, Institut Curie CNRS, UMR144, 26 rue d’Ulm, 75248 Paris cedex 05, France
| | - Olena Pylypenko
- Structural Motility, Institut Curie CNRS, UMR144, 26 rue d’Ulm, 75248 Paris cedex 05, France
| | - Tatiana Isabet
- Structural Motility, Institut Curie CNRS, UMR144, 26 rue d’Ulm, 75248 Paris cedex 05, France
| | - Monalisa Mukherjea
- 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 M. Houdusse
- Structural Motility, Institut Curie CNRS, UMR144, 26 rue d’Ulm, 75248 Paris cedex 05, France
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Abstract
A mere forty years ago it was unclear what motor molecules exist in cells that could be responsible for the variety of nonmuscle cell movements, including the "saltatory cytoplasmic particle movements" apparent by light microscopy. One wondered whether nonmuscle cells might have a myosin-like molecule, well known to investigators of muscle. Now we know that there are more than a hundred different molecular motors in eukaryotic cells that drive numerous biological processes and organize the cell's dynamic city plan. Furthermore, in vitro motility assays, taken to the single-molecule level using techniques of physics, have allowed detailed characterization of the processes by which motor molecules transduce the chemical energy of ATP hydrolysis into mechanical movement. Molecular motor research is now at an exciting threshold of being able to enter into the realm of clinical applications.
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Isaji M, Lenartowska M, Noguchi T, Frank DJ, Miller KG. Myosin VI regulates actin structure specialization through conserved cargo-binding domain sites. PLoS One 2011; 6:e22755. [PMID: 21853045 PMCID: PMC3154908 DOI: 10.1371/journal.pone.0022755] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2011] [Accepted: 06/30/2011] [Indexed: 11/18/2022] Open
Abstract
Actin structures are often stable, remaining unchanged in organization for the lifetime of a differentiated cell. Little is known about stable actin structure formation, organization, or maintenance. During Drosophila spermatid individualization, long-lived actin cones mediate cellular remodeling. Myosin VI is necessary for building the dense meshwork at the cones' fronts. We test several ideas for myosin VI's mechanism of action using domain deletions or site-specific mutations of myosin VI. The head (motor) and globular tail (cargo-binding) domains were both needed for localization at the cone front and dense meshwork formation. Several conserved partner-binding sites in the globular tail previously identified in vertebrate myosin VI were critical for function in cones. Localization and promotion of proper actin organization were separable properties of myosin VI. A vertebrate myosin VI was able to localize and function, indicating that functional properties are conserved. Our data eliminate several models for myosin VI's mechanism of action and suggest its role is controlling organization and action of actin assembly regulators through interactions at conserved sites. The Drosophila orthologues of interaction partners previously identified for vertebrate myosin VI are likely not required, indicating novel partners mediate this effect. These data demonstrate that generating an organized and functional actin structure in this cell requires multiple activities coordinated by myosin VI.
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Affiliation(s)
- Mamiko Isaji
- Department of Biology, Washington University in St. Louis, St. Louis, Missouri, United States of America
| | - Marta Lenartowska
- Faculty of Biology and Earth Sciences, Institute of General and Molecular Biology, Laboratory of Developmental Biology, Nicolaus Copernicus University, Torun, Poland
| | - Tatsuhiko Noguchi
- Laboratory for Morphogenetic Signaling, Center for Developmental Biology, RIKEN Kobe, Kobe, Japan
| | - Deborah J. Frank
- Department of Biology, Washington University in St. Louis, St. Louis, Missouri, United States of America
| | - Kathryn G. Miller
- Department of Biology, Washington University in St. Louis, St. Louis, Missouri, United States of America
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Hartman MA, Finan D, Sivaramakrishnan S, Spudich JA. Principles of unconventional myosin function and targeting. Annu Rev Cell Dev Biol 2011; 27:133-55. [PMID: 21639800 DOI: 10.1146/annurev-cellbio-100809-151502] [Citation(s) in RCA: 123] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Unconventional myosins are a superfamily of actin-based motors implicated in diverse cellular processes. In recent years, much progress has been made in describing their biophysical properties, and headway has been made into analyzing their cellular functions. Here, we focus on the principles that guide in vivo motor function and targeting to specific cellular locations. Rather than describe each motor comprehensively, we outline the major themes that emerge from research across the superfamily and use specific examples to illustrate each. In presenting the data in this format, we seek to identify open questions in each field as well as to point out commonalities between them. To advance our understanding of myosins' roles in vivo, clearly we must identify their cellular cargoes and the protein complexes that regulate motor attachment to fully appreciate their functions on the cellular and developmental levels.
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Affiliation(s)
- M Amanda Hartman
- Department of Biochemistry, Stanford University, Stanford, California 94305, USA
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