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Horsthemke M, Arnaud CA, Hanley PJ. Are the class 18 myosins Myo18A and Myo18B specialist sarcomeric proteins? Front Physiol 2024; 15:1401717. [PMID: 38784114 PMCID: PMC11112018 DOI: 10.3389/fphys.2024.1401717] [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: 03/15/2024] [Accepted: 04/22/2024] [Indexed: 05/25/2024] Open
Abstract
Initially, the two members of class 18 myosins, Myo18A and Myo18B, appeared to exhibit highly divergent functions, complicating the assignment of class-specific functions. However, the identification of a striated muscle-specific isoform of Myo18A, Myo18Aγ, suggests that class 18 myosins may have evolved to complement the functions of conventional class 2 myosins in sarcomeres. Indeed, both genes, Myo18a and Myo18b, are predominantly expressed in the heart and somites, precursors of skeletal muscle, of developing mouse embryos. Genetic deletion of either gene in mice is embryonic lethal and is associated with the disorganization of cardiac sarcomeres. Moreover, Myo18Aγ and Myo18B localize to sarcomeric A-bands, albeit the motor (head) domains of these unconventional myosins have been both deduced and biochemically demonstrated to exhibit negligible ATPase activity, a hallmark of motor proteins. Instead, Myo18Aγ and Myo18B presumably coassemble with thick filaments and provide structural integrity and/or internal resistance through interactions with F-actin and/or other proteins. In addition, Myo18Aγ and Myo18B may play distinct roles in the assembly of myofibrils, which may arise from actin stress fibers containing the α-isoform of Myo18A, Myo18Aα. The β-isoform of Myo18A, Myo18Aβ, is similar to Myo18Aα, except that it lacks the N-terminal extension, and may serve as a negative regulator through heterodimerization with either Myo18Aα or Myo18Aγ. In this review, we contend that Myo18Aγ and Myo18B are essential for myofibril structure and function in striated muscle cells, while α- and β-isoforms of Myo18A play diverse roles in nonmuscle cells.
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Affiliation(s)
- Markus Horsthemke
- IMM Institute for Molecular Medicine, HMU Health and Medical University Potsdam, Potsdam, Germany
| | - Charles-Adrien Arnaud
- IMM Institute for Molecular Medicine, HMU Health and Medical University Potsdam, Potsdam, Germany
- Department of Medicine, Science Faculty, MSB Medical School Berlin, Berlin, Germany
| | - Peter J. Hanley
- IMM Institute for Molecular Medicine, HMU Health and Medical University Potsdam, Potsdam, Germany
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2
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Wu X, Chu M, Ma X, Pei J, Xiong L, Guo X, Liang C, Yan P. Genome-Wide Identification of RNA Editing Sites Affecting Muscle Development in Yak. Front Vet Sci 2022; 9:871814. [PMID: 35836505 PMCID: PMC9274240 DOI: 10.3389/fvets.2022.871814] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2022] [Accepted: 06/07/2022] [Indexed: 12/24/2022] Open
Abstract
Skeletal muscle growth and development is a complicated process that is regulated at multiple steps and by numerous myogenesis genes. RNA editing represents one of the events at the post-transcriptional level, which contributes to the diversity of transcriptome and proteome by altering the nucleotides of RNAs. However, RNA editing events in the skeletal muscle of yaks are still not well defined. This study conducted whole-genome RNA-editing identification in skeletal muscle of yaks at embryonic stage (ES) and adult stage (AS). We found a total of 11,168 unique RNA editing sites, most of which were detected in the intergenic region. After annotation, we totally identified 2,718 editing sites within coding regions, among which 858 were missense changes. Moreover, totally 322 editing sites in the 3′ untranslated regions (UTR) were also predicted to alter the set of miRNA target sites, indicating that RNA editing may be involved in translational repression or mRNA degradation. We found 838 RNA editing sites (involving 244 common genes) that are edited differentially in ES as compared to AS. According to the KEGG enrichment analysis, these differentially edited genes were mainly involved in pathways highly related to skeletal muscle development and myogenesis, including MAPK, AMPK, Wnt, and PI3K-Akt signaling pathways. Altogether, our work presents the first characterization of RNA editing sites within yak skeletal muscles on a genome-wide scale and enhances our understanding of the mechanism of skeletal muscle development and myogenesis.
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3
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Matozo T, Kogachi L, de Alencar BC. Myosin motors on the pathway of viral infections. Cytoskeleton (Hoboken) 2022; 79:41-63. [PMID: 35842902 DOI: 10.1002/cm.21718] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2022] [Revised: 06/25/2022] [Accepted: 07/07/2022] [Indexed: 01/30/2023]
Abstract
Molecular motors are microscopic machines that use energy from adenosine triphosphate (ATP) hydrolysis to generate movement. While kinesins and dynein are molecular motors associated with microtubule tracks, myosins bind to and move on actin filaments. Mammalian cells express several myosin motors. They power cellular processes such as endo- and exocytosis, intracellular trafficking, transcription, migration, and cytokinesis. As viruses navigate through cells, they may take advantage or be hindered by host components and machinery, including the cytoskeleton. This review delves into myosins' cell roles and compares them to their reported functions in viral infections. In most cases, the previously described myosin functions align with their reported role in viral infections, although not in all cases. This opens the possibility that knowledge obtained from studying myosins in viral infections might shed light on new physiological roles for myosins in cells. However, given the high number of myosins expressed and the variety of viruses investigated in the different studies, it is challenging to infer whether the interactions found are specific to a single virus or can be applied to other viruses with the same characteristics. We conclude that the participation of myosins in viral cycles is still a largely unexplored area, especially concerning unconventional myosins.
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Affiliation(s)
- Tais Matozo
- Departamento de Imunologia, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo, Sao Paulo, Brazil
| | - Leticia Kogachi
- Departamento de Imunologia, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo, Sao Paulo, Brazil
| | - Bruna Cunha de Alencar
- Departamento de Imunologia, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo, Sao Paulo, Brazil
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4
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Hsu NW, Chou KC, Wang YTT, Hung CL, Kuo CF, Tsai SY. Building a model for predicting metabolic syndrome using artificial intelligence based on an investigation of whole-genome sequencing. J Transl Med 2022; 20:190. [PMID: 35484552 PMCID: PMC9052619 DOI: 10.1186/s12967-022-03379-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2022] [Accepted: 04/04/2022] [Indexed: 12/02/2022] Open
Abstract
Background The circadian system is responsible for regulating various physiological activities and behaviors and has been gaining recognition. The circadian rhythm is adjusted in a 24-h cycle and has transcriptional–translational feedback loops. When the circadian rhythm is interrupted, affecting the expression of circadian genes, the phenotypes of diseases could amplify. For example, the importance of maintaining the internal temporal homeostasis conferred by the circadian system is revealed as mutations in genes coding for core components of the clock result in diseases. This study will investigate the association between circadian genes and metabolic syndromes in a Taiwanese population. Methods We performed analysis using whole-genome sequencing, read vcf files and set target circadian genes to determine if there were variants on target genes. In this study, we have investigated genetic contribution of circadian-related diseases using population-based next generation whole genome sequencing. We also used significant SNPs to create a metabolic syndrome prediction model. Logistic regression, random forest, adaboost, and neural network were used to predict metabolic syndrome. In addition, we used random forest model variables importance matrix to select 40 more significant SNPs, which were subsequently incorporated to create new prediction models and to compare with previous models. The data was then utilized for training set and testing set using five-fold cross validation. Each model was evaluated with the following criteria: area under the receiver operating characteristics curve (AUC), precision, F1 score, and average precision (the area under the precision recall curve). Results After searching significant variants, we used Chi-Square tests to find some variants. We found 186 significant SNPs, and four predicting models which used 186 SNPs (logistic regression, random forest, adaboost and neural network), AUC were 0.68, 0.8, 0.82, 0.81 respectively. The F1 scores were 0.412, 0.078, 0.295, 0.552, respectively. The other three models which used the 40 SNPs (logistic regression, adaboost and neural network), AUC were 0.82, 0.81, 0.81 respectively. The F1 scores were 0.584, 0.395, 0.574, respectively. Conclusions Circadian gene defect may also contribute to metabolic syndrome. Our study found several related genes and building a simple model to predict metabolic syndrome. Supplementary Information The online version contains supplementary material available at 10.1186/s12967-022-03379-7.
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Affiliation(s)
- Nai-Wei Hsu
- Department of Medicine, Mackay Medical College, New Taipei City, Taiwan
| | - Kai-Chen Chou
- Department of Laboratory Medicine, MacKay Memorial Hospital, Taipei City, Taiwan
| | - Yu-Ting Tina Wang
- Department of Laboratory Medicine, MacKay Memorial Hospital, Taipei City, Taiwan
| | - Chung-Lieh Hung
- Department of Medicine, Mackay Medical College, New Taipei City, Taiwan.,Institute of Biomedical Sciences, Mackay Medical College, New Taipei City, Taiwan
| | - Chien-Feng Kuo
- Department of Medicine, Mackay Medical College, New Taipei City, Taiwan.,Department of Nursing, MacKay Junior College of Medicine, Nursing and Management, New Taipei City, Taiwan.,Division of Infectious Diseases, Department of Internal Medicine, Mackay Memorial Hospital, Taipei, Taiwan
| | - Shin-Yi Tsai
- Department of Medicine, Mackay Medical College, New Taipei City, Taiwan. .,Department of Laboratory Medicine, MacKay Memorial Hospital, Taipei City, Taiwan. .,Department of Health Policy and Management, Johns Hopkins Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland, 21205, USA. .,Institute of Biomedical Sciences, Mackay Medical College, New Taipei City, Taiwan. .,Institute of Long-Term Care, Mackay Medical College, New Taipei City, Taiwan.
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5
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Latham SL, Weiß N, Schwanke K, Thiel C, Croucher DR, Zweigerdt R, Manstein DJ, Taft MH. Myosin-18B Regulates Higher-Order Organization of the Cardiac Sarcomere through Thin Filament Cross-Linking and Thick Filament Dynamics. Cell Rep 2021; 32:108090. [PMID: 32877672 DOI: 10.1016/j.celrep.2020.108090] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2020] [Revised: 07/07/2020] [Accepted: 08/07/2020] [Indexed: 12/20/2022] Open
Abstract
MYO18B loss-of-function mutations and depletion significantly compromise the structural integrity of striated muscle sarcomeres. The molecular function of the encoded protein, myosin-18B (M18B), within the developing muscle is unknown. Here, we demonstrate that recombinant M18B lacks motor ATPase activity and harbors previously uncharacterized N-terminal actin-binding domains, properties that make M18B an efficient actin cross-linker and molecular brake capable of regulating muscle myosin-2 contractile forces. Spatiotemporal analysis of M18B throughout cardiomyogenesis and myofibrillogenesis reveals that this structural myosin undergoes nuclear-cytoplasmic redistribution during myogenic differentiation, where its incorporation within muscle stress fibers coincides with actin striation onset. Furthermore, this analysis shows that M18B is directly integrated within the muscle myosin thick filament during myofibril maturation. Altogether, our data suggest that M18B has evolved specific biochemical properties that allow it to define and maintain sarcomeric organization from within the thick filament via its dual actin cross-linking and motor modulating capabilities.
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Affiliation(s)
- Sharissa L Latham
- Institute for Biophysical Chemistry, Hannover Medical School, Hannover 30625, Germany; The Kinghorn Cancer Centre, Garvan Institute of Medical Research, Darlinghurst, NSW 2010, Australia; St Vincent's Hospital Clinical School, UNSW Sydney, NSW 2052, Australia
| | - Nadine Weiß
- Institute for Biophysical Chemistry, Hannover Medical School, Hannover 30625, Germany
| | - Kristin Schwanke
- Leibniz Research Laboratories for Biotechnology and Artificial Organs (LEBAO), Department of Cardiac, Thoracic, Transplantation and Vascular Surgery, REBIRTH-Cluster of Excellence, Hannover Medical School, Hannover 30625, Germany
| | - Claudia Thiel
- Institute for Biophysical Chemistry, Hannover Medical School, Hannover 30625, Germany
| | - David R Croucher
- The Kinghorn Cancer Centre, Garvan Institute of Medical Research, Darlinghurst, NSW 2010, Australia; St Vincent's Hospital Clinical School, UNSW Sydney, NSW 2052, Australia
| | - Robert Zweigerdt
- Leibniz Research Laboratories for Biotechnology and Artificial Organs (LEBAO), Department of Cardiac, Thoracic, Transplantation and Vascular Surgery, REBIRTH-Cluster of Excellence, Hannover Medical School, Hannover 30625, Germany
| | - Dietmar J Manstein
- Institute for Biophysical Chemistry, Hannover Medical School, Hannover 30625, Germany
| | - Manuel H Taft
- Institute for Biophysical Chemistry, Hannover Medical School, Hannover 30625, Germany.
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6
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Wang L, Chitano P, Seow CY. Filament evanescence of myosin II and smooth muscle function. J Gen Physiol 2021; 153:211814. [PMID: 33606000 PMCID: PMC7901143 DOI: 10.1085/jgp.202012781] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Accepted: 01/19/2021] [Indexed: 01/02/2023] Open
Abstract
Smooth muscle is an integral part of hollow organs. Many of them are constantly subjected to mechanical forces that alter organ shape and modify the properties of smooth muscle. To understand the molecular mechanisms underlying smooth muscle function in its dynamic mechanical environment, a new paradigm has emerged that depicts evanescence of myosin filaments as a key mechanism for the muscle’s adaptation to external forces in order to maintain optimal contractility. Unlike the bipolar myosin filaments of striated muscle, the side-polar filaments of smooth muscle appear to be less stable, capable of changing their lengths through polymerization and depolymerization (i.e., evanescence). In this review, we summarize accumulated knowledge on the structure and mechanism of filament formation of myosin II and on the influence of ionic strength, pH, ATP, myosin regulatory light chain phosphorylation, and mechanical perturbation on myosin filament stability. We discuss the scenario of intracellular pools of monomeric and filamentous myosin, length distribution of myosin filaments, and the regulatory mechanisms of filament lability in contraction and relaxation of smooth muscle. Based on recent findings, we suggest that filament evanescence is one of the fundamental mechanisms underlying smooth muscle’s ability to adapt to the external environment and maintain optimal function. Finally, we briefly discuss how increased ROCK protein expression in asthma may lead to altered myosin filament stability, which may explain the lack of deep-inspiration–induced bronchodilation and bronchoprotection in asthma.
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Affiliation(s)
- Lu Wang
- Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada.,The Centre for Heart Lung Innovation, University of British Columbia, Vancouver, British Columbia, Canada
| | - Pasquale Chitano
- Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, British Columbia, Canada.,The Centre for Heart Lung Innovation, University of British Columbia, Vancouver, British Columbia, Canada
| | - Chun Y Seow
- Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, British Columbia, Canada.,The Centre for Heart Lung Innovation, University of British Columbia, Vancouver, British Columbia, Canada
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7
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Ouyang Z, Zhao S, Yao S, Wang J, Cui Y, Wei K, Jiu Y. Multifaceted Function of Myosin-18, an Unconventional Class of the Myosin Superfamily. Front Cell Dev Biol 2021; 9:632445. [PMID: 33634131 PMCID: PMC7900500 DOI: 10.3389/fcell.2021.632445] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Accepted: 01/04/2021] [Indexed: 12/11/2022] Open
Abstract
Myosin is a diverse superfamily of motor proteins responsible for actin-based motility and contractility in eukaryotic cells. Myosin-18 family, including myosin-18A and myosin-18B, belongs to an unconventional class of myosin, which lacks ATPase motor activity, and the investigations on their functions and molecular mechanisms in vertebrate development and diseases have just been initiated in recent years. Myosin-18A is ubiquitously expressed in mammalian cells, whereas myosin-18B shows strong enrichment in striated muscles. Myosin-18 family is important for cell motility, sarcomere formation, and mechanosensing, mostly by interacting with other cytoskeletal proteins and cellular apparatus. Myosin-18A participates in several intracellular transport processes, such as Golgi trafficking, and has multiple roles in focal adhesions, stress fibers, and lamellipodia formation. Myosin-18B, on the other hand, participates in actomyosin alignment and sarcomere assembly, thus relating to cell migration and muscle contractility. Mutations of either Myo18a or Myo18b cause cardiac developmental defects in mouse, emphasizing their crucial role in muscle development and cardiac diseases. In this review, we revisit the discovery history of myosin-18s and summarize the evolving understanding of the molecular functions of myosin-18A and myosin-18B, with an emphasis on their separate yet closely related functions in cell motility and contraction. Moreover, we discuss the diseases tightly associated with myosin-18s, especially cardiovascular defects and cancer, as well as highlight the unanswered questions and potential future research perspectives on myosin-18s.
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Affiliation(s)
- Zhaohui Ouyang
- Institute for Regenerative Medicine, Shanghai East Hospital, Shanghai Key Laboratory of Signaling and Disease Research, Frontier Science Center for Stem Cell Research, Ministry of Education of China, School of Life Sciences and Technology, Tongji University, Shanghai, China
| | - Shuangshuang Zhao
- The Joint Program in Infection and Immunity, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangzhou, China.,Institut Pasteur of Shanghai, Chinese Academy of Sciences, Shanghai, China
| | - Su Yao
- Institute for Regenerative Medicine, Shanghai East Hospital, Shanghai Key Laboratory of Signaling and Disease Research, Frontier Science Center for Stem Cell Research, Ministry of Education of China, School of Life Sciences and Technology, Tongji University, Shanghai, China
| | - Jing Wang
- Unit of Cell Biology and Imaging Study of Pathogen Host Interaction, The Center for Microbes, Development and Health, Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Chinese Academy of Sciences, Shanghai, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Yanqin Cui
- The Joint Program in Infection and Immunity, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangzhou, China.,Institut Pasteur of Shanghai, Chinese Academy of Sciences, Shanghai, China
| | - Ke Wei
- Institute for Regenerative Medicine, Shanghai East Hospital, Shanghai Key Laboratory of Signaling and Disease Research, Frontier Science Center for Stem Cell Research, Ministry of Education of China, School of Life Sciences and Technology, Tongji University, Shanghai, China
| | - Yaming Jiu
- The Joint Program in Infection and Immunity, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangzhou, China.,Institut Pasteur of Shanghai, Chinese Academy of Sciences, Shanghai, China.,Unit of Cell Biology and Imaging Study of Pathogen Host Interaction, The Center for Microbes, Development and Health, Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Chinese Academy of Sciences, Shanghai, China.,University of Chinese Academy of Sciences, Beijing, China
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8
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Cao C, Zhang C, Sun Y, Mu Z, Shen Q. Myosin18B predicts favorable prognosis of cutaneous squamous-cell carcinoma. Genes Genomics 2021; 43:371-378. [PMID: 33555505 DOI: 10.1007/s13258-021-01037-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2020] [Accepted: 01/02/2021] [Indexed: 02/08/2023]
Abstract
BACKGROUND Myosin18 family, including Myosin18A (MYO18A) and Myosin18B (MYO18B), are newly-identified Myosins in Myosin superfamily. The expression and function of Myosin18 family in cancer progression is still controversial, and in cutaneous squamous-cell carcinoma (cSCC) is totally unknown. OBJECTIVE To investigate the expression and prognostic significance of Myosin18 family in cSCC. METHODS In this study, the expressions of MYO18 family, including MYO18A and MYO18B were detected in six pairs of cSCCs and corresponding normal tissues with qRT-PCR. MYO18A and MYO18B expressions and intracellular locations in 80 cSCCs were detected with immunohistochemistry. The clinical significance was evaluated by analyzing the correlation between MYO18 family and clinicopathological factors. The prognostic significance of MYO18 family was estimated by univariate analysis with log-rank test, and by multivariate analysis by Cox-regression model. RESULTS The percentages of high MYO18A and MYO18B in cSCC were 43.75% and 36.25%, respectively. High expression of MYO18A (P = 0.035) and MYO18B (P = 0.032) were both associated with less tumor size. MYO18A had no significant influence on sSCC prognosis (P = 0.686), but low expression of MYO18B was proved to be significantly associated with poor outcome of cSCC (P = 0.014). MYO18B was confirmed as an independent prognostic biomarker of cSCC (P = 0.002), indicating the favorable outcome. CONCLUSION The expression of MYO18B was an independent prognostic biomarker of cSCC, predicting the favorable prognosis independently. Investigating the expression of MYO18B can help stratify the subset of high-risk cSCC patients for more potent treatment and post-operational surveillance.
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Affiliation(s)
- Can Cao
- Departments of Dermatology, the Second Affiliated Hospital of Shandong First Medical University, Taian, 271000, Shandong, China
| | - Chao Zhang
- Departments of Dermatology, the Second Affiliated Hospital of Shandong First Medical University, Taian, 271000, Shandong, China
| | - Ying Sun
- Departments of Dermatology, the Second Affiliated Hospital of Shandong First Medical University, Taian, 271000, Shandong, China
| | - Zhen Mu
- Departments of Dermatology, the Second Affiliated Hospital of Shandong First Medical University, Taian, 271000, Shandong, China
| | - Qin Shen
- Department of Dermatology, Hubei Provincial Hospital of Traditional Chinese Medicine, No.856, Luoyu Road, Hongshan District, Wuhan, 430061, Hubei, China. .,Department of Dermatology, Hubei Provincial Academy of Traditional Chinese Medicine, Wuhan, 430061, Hubei, China.
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9
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Altuame FD, Haldeman-Englert C, Cupler E, Al Muhaizea MA, Al-Zaidan HI, Hashem M, Alkuraya FS. Further delineation of MYO18B-related autosomal recessive Klippel-Feil syndrome with myopathy and facial dysmorphism. Am J Med Genet A 2020; 185:370-376. [PMID: 33179433 DOI: 10.1002/ajmg.a.61957] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2020] [Revised: 09/26/2020] [Accepted: 10/21/2020] [Indexed: 11/09/2022]
Abstract
Klippel-Feil syndrome 4 (KFS4; MIM# 616549) is an autosomal recessive disorder caused by biallelic pathogenic variants in MYO18B and comprises, in addition to Klippel-Feil anomaly (KFA), nemaline myopathy, facial dysmorphism, and short stature. We aim to outline the natural history of KFS4 and provide an updated description of its clinical, radiological, laboratory, and molecular findings. We comprehensively analyzed the medical records of 6 Saudi and 1 American patients (including 5 previously unpublished cases) with a molecularly confirmed diagnosis of KFS4. All patients had myopathy of varying severity that followed a slowly progressive or non-progressive course, affecting primarily the proximal musculature of the lower limb although hand involvement with distal arthrogryposis and abnormal interphalangeal creases was also observed. KFA and characteristic dysmorphic features, including ptosis and bulbous nose, were observed in all but two patients. The causal MYO18B variants were a founder NM_032608.5:c.6905C>A; p.(Ser2302*) variant in the Saudi patients (P1-P6) and a novel MYO18B homozygous variant (c.6660_6670del;p.[Arg2220Serfs*74]) in the American Caucasian patient (P7). We report the phenotypic and genetic findings in seven patients with KFS4. We describe the natural history of this disease, confirm myopathy as a universal feature and describe its pattern and progression, and note interesting differences between the phenotypes observed in patients with KFA and those without.
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Affiliation(s)
- Fadie D Altuame
- College of Medicine, Alfaisal University, Riyadh, Saudi Arabia
| | - Chad Haldeman-Englert
- Department of Medical Genetics, Mission Fullerton Genetics Center, Asheville, North Carolina, USA
| | - Edward Cupler
- Department of Neurosciences, King Faisal Specialist Hospital and Research Center, Jeddah, Saudi Arabia
| | - Mohammad A Al Muhaizea
- Department of Neurosciences, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
| | - Hamad I Al-Zaidan
- Department of Medical Genetics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
| | - Mais Hashem
- Department of Genetics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
| | - Fowzan S Alkuraya
- Department of Genetics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
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10
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Abstract
Myosins constitute a superfamily of actin-based molecular motor proteins that mediates a variety of cellular activities including muscle contraction, cell migration, intracellular transport, the formation of membrane projections, cell adhesion, and cell signaling. The 12 myosin classes that are expressed in humans share sequence similarities especially in the N-terminal motor domain; however, their enzymatic activities, regulation, ability to dimerize, binding partners, and cellular functions differ. It is becoming increasingly apparent that defects in myosins are associated with diseases including cardiomyopathies, colitis, glomerulosclerosis, neurological defects, cancer, blindness, and deafness. Here, we review the current state of knowledge regarding myosins and disease.
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11
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Formation of Aberrant Myotubes by Myoblasts Lacking Myosin VI Is Associated with Alterations in the Cytoskeleton Organization, Myoblast Adhesion and Fusion. Cells 2020; 9:cells9071673. [PMID: 32664530 PMCID: PMC7408620 DOI: 10.3390/cells9071673] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2020] [Revised: 07/03/2020] [Accepted: 07/09/2020] [Indexed: 02/06/2023] Open
Abstract
We have previously postulated that unconventional myosin VI (MVI) could be involved in myoblast differentiation. Here, we addressed the mechanism(s) of its involvement using primary myoblast culture derived from the hindlimb muscles of Snell’s waltzer mice, the natural MVI knockouts (MVI-KO). We observed that MVI-KO myotubes were formed faster than control heterozygous myoblasts (MVI-WT), with a three-fold increase in the number of myosac-like myotubes with centrally positioned nuclei. There were also changes in the levels of the myogenic transcription factors Pax7, MyoD and myogenin. This was accompanied by changes in the actin cytoskeleton and adhesive structure organization. We observed significant decreases in the levels of proteins involved in focal contact formation, such as talin and focal adhesion kinase (FAK). Interestingly, the levels of proteins involved in intercellular communication, M-cadherin and drebrin, were also affected. Furthermore, time-dependent alterations in the levels of the key proteins for myoblast membrane fusion, myomaker and myomerger, without effect on their cellular localization, were observed. Our data indicate that in the absence of MVI, the mechanisms controlling cytoskeleton organization, as well as myoblast adhesion and fusion, are dysregulated, leading to the formation of aberrant myotubes.
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12
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Cook AW, Gough RE, Toseland CP. Nuclear myosins - roles for molecular transporters and anchors. J Cell Sci 2020; 133:133/11/jcs242420. [PMID: 32499319 DOI: 10.1242/jcs.242420] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The myosin family of molecular motors are well-characterised cytoskeletal proteins. However, myosins are also present in the nucleus, where they have been shown to have roles in transcription, DNA repair and viral infections. Despite their involvement in these fundamental cellular processes, our understanding of these functions and their regulation remains limited. Recently, research on nuclear myosins has been gathering pace, and this Review will evaluate the current state of the field. Here, we will focus on the variation in structure of nuclear myosins, their nuclear import and their roles within transcription, DNA damage, chromatin organisation and viral infections. We will also consider both the biochemical and biophysical properties and restraints that are placed on these multifunctional motors, and how they link to their cytoplasmic counterparts. By highlighting these properties and processes, we show just how integral nuclear myosins are for cellular survival.
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Affiliation(s)
- Alexander W Cook
- Department of Oncology and Metabolism, University of Sheffield, Sheffield S10 2RX, UK
| | - Rosemarie E Gough
- Department of Oncology and Metabolism, University of Sheffield, Sheffield S10 2RX, UK
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14
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Abstract
Class XVIII myosins represent a branch of the myosin family tree characterized by the presence of large N- and C-terminal extensions flanking a generic myosin core. These myosins display the highest sequence similarity to conventional class II muscle myosins and are compatible with but not restricted to myosin-2 contractile structures. Instead, they fulfill their functions at diverse localities, such as lamella, actomyosin bundles, the Golgi apparatus, focal adhesions, the cell membrane, and within sarcomeres. Sequence comparison of active-site residues and biochemical data available thus far indicate that this myosin class lacks active ATPase-driven motor activity, suggesting that its members function as structural myosins. An emerging body of evidence indicates that this structural capability is essential for the organization, maturation, and regulation of the contractile machinery in both muscle and nonmuscle cells. This is supported by the clear association of myosin-18A (Myo18A) and myosin-18B (Myo18B) dysregulation with diseases such as cancer and various myopathies.
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15
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Schieffer KM, Varga E, Miller KE, Agarwal V, Koboldt DC, Brennan P, Kelly B, Dave-Wala A, Pierson CR, Finlay JL, AbdelBaki MS, White P, Magrini V, Wilson RK, Mardis ER, Cottrell CE. Expanding the clinical history associated with syndromic Klippel-Feil: A unique case of comorbidity with medulloblastoma. Eur J Med Genet 2019; 62:103701. [PMID: 31195167 DOI: 10.1016/j.ejmg.2019.103701] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Revised: 05/29/2019] [Accepted: 06/09/2019] [Indexed: 11/28/2022]
Abstract
Klippel-Feil syndrome (KFS) is an exceedingly rare constitutional disorder in which a paucity of knowledge exists about the disease and its associated morbidity and mortality. We present a 4-year-old male with KFS, who notably was also diagnosed with large-cell anaplastic medulloblastoma. We evaluated the genetic basis of co-occurring KFS and medulloblastoma and the role of MYO18B as related to medulloblastoma. Constitutional and somatic variant and copy number analyses were performed from DNA-based exome studies, along with RNA-sequencing of tumor tissue, to elucidate the genetic etiology of the co-existing disease states. We identified novel constitutional compound heterozygous frameshift variants (NM_032608.5: p.Leu2257SerfsTer16 and p.Arg2220SerfsTer74) each encoding a premature stop of translation in MYO18B, consistent with a diagnosis of KFS. We did not identify any somatic variants of known relevance or disease-relevant therapeutic targets in the tumor. The somatic copy number profile was suggestive of Group 3γ medulloblastoma. Relative to pediatric brain tumors, medulloblastoma, particularly, Group 3, had increased gene expression of MYO18B. In summary, coexisting constitutional and somatic diagnoses in this patient enabled the elucidation of the genetic etiology of KFS and provided support for the role of MYO18B in tumor suppression.
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Affiliation(s)
- Kathleen M Schieffer
- Institute for Genomic Medicine, Nationwide Children's Hospital, Columbus, OH, USA.
| | - Elizabeth Varga
- Institute for Genomic Medicine, Nationwide Children's Hospital, Columbus, OH, USA; Division of Hematology, Oncology and Bone Marrow Transplant, Nationwide Children's Hospital, Columbus, OH, USA
| | - Katherine E Miller
- Institute for Genomic Medicine, Nationwide Children's Hospital, Columbus, OH, USA
| | - Vibhuti Agarwal
- Division of Hematology, Oncology and Bone Marrow Transplant, Nationwide Children's Hospital, Columbus, OH, USA
| | - Daniel C Koboldt
- Institute for Genomic Medicine, Nationwide Children's Hospital, Columbus, OH, USA; Department of Pediatrics, The Ohio State University College of Medicine, Columbus, OH, USA
| | - Patrick Brennan
- Institute for Genomic Medicine, Nationwide Children's Hospital, Columbus, OH, USA
| | - Benjamin Kelly
- Institute for Genomic Medicine, Nationwide Children's Hospital, Columbus, OH, USA
| | - Ashita Dave-Wala
- Institute for Genomic Medicine, Nationwide Children's Hospital, Columbus, OH, USA
| | - Christopher R Pierson
- Department of Pathology and Laboratory Medicine, Nationwide Children's Hospital, Columbus, OH, USA; Department of Biomedical Education and Anatomy, The Ohio State University, Columbus, OH, USA
| | - Jonathan L Finlay
- Division of Hematology, Oncology and Bone Marrow Transplant, Nationwide Children's Hospital, Columbus, OH, USA; Department of Pediatrics, The Ohio State University College of Medicine, Columbus, OH, USA
| | - Mohamed S AbdelBaki
- Division of Hematology, Oncology and Bone Marrow Transplant, Nationwide Children's Hospital, Columbus, OH, USA
| | - Peter White
- Institute for Genomic Medicine, Nationwide Children's Hospital, Columbus, OH, USA; Department of Pediatrics, The Ohio State University College of Medicine, Columbus, OH, USA
| | - Vincent Magrini
- Institute for Genomic Medicine, Nationwide Children's Hospital, Columbus, OH, USA; Department of Pediatrics, The Ohio State University College of Medicine, Columbus, OH, USA
| | - Richard K Wilson
- Institute for Genomic Medicine, Nationwide Children's Hospital, Columbus, OH, USA; Department of Pediatrics, The Ohio State University College of Medicine, Columbus, OH, USA
| | - Elaine R Mardis
- Institute for Genomic Medicine, Nationwide Children's Hospital, Columbus, OH, USA; Department of Pediatrics, The Ohio State University College of Medicine, Columbus, OH, USA
| | - Catherine E Cottrell
- Institute for Genomic Medicine, Nationwide Children's Hospital, Columbus, OH, USA; Department of Pediatrics, The Ohio State University College of Medicine, Columbus, OH, USA; Department of Pathology, The Ohio State University College of Medicine, Columbus, OH, USA
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16
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Abstract
"Myosin" is famous as a component of muscle fibrils, but the majority of myosin family members act elsewhere with roles unrelated to muscle contraction. The biological functions of a relatively new family of these unconventional myosins, myosins 18A and 18B, are poorly understood. New research from Horsthemke et al. describes a new isoform (Myo18Aγ) that is essential for heart function and viability in mice. Their findings both support and contradict other work in the field and raise new questions about the roles of myosin 18 proteins in vivo.
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Affiliation(s)
- Elizabeth J Luna
- From the Division of Cell Biology and Imaging, Department of Radiology, University of Massachusetts Medical School, Worcester, Massachusetts 01655
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17
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Grimes KM, Prasad V, McNamara JW. Supporting the heart: Functions of the cardiomyocyte's non-sarcomeric cytoskeleton. J Mol Cell Cardiol 2019; 131:187-196. [PMID: 30978342 DOI: 10.1016/j.yjmcc.2019.04.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/02/2018] [Revised: 04/02/2019] [Accepted: 04/05/2019] [Indexed: 02/06/2023]
Abstract
The non-contractile cytoskeleton in cardiomyocytes is comprised of cytoplasmic actin, microtubules, and intermediate filaments. In addition to providing mechanical support to these cells, these structures are important effectors of tension-sensing and signal transduction and also provide networks for the transport of proteins and organelles. The majority of our knowledge on the function and structure of these cytoskeletal networks comes from research on proliferative cell types. However, in recent years, researchers have begun to show that there are important cardiomyocyte-specific functions of the cytoskeleton. Here we will discuss the current state of cytoskeletal biology in cardiomyocytes, as well as research from other cell types, that together suggest there is a wealth of knowledge on cardiac health and disease waiting to be uncovered through exploration of the complex signaling networks of cardiomyocyte non-sarcomeric cytoskeletal proteins.
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Affiliation(s)
- Kelly M Grimes
- Department of Pediatrics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA.
| | - Vikram Prasad
- Department of Pediatrics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
| | - James W McNamara
- Heart, Lung and Vascular Institute, University of Cincinnati, Cincinnati, OH, USA
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18
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Jiu Y, Kumari R, Fenix AM, Schaible N, Liu X, Varjosalo M, Krishnan R, Burnette DT, Lappalainen P. Myosin-18B Promotes the Assembly of Myosin II Stacks for Maturation of Contractile Actomyosin Bundles. Curr Biol 2018; 29:81-92.e5. [PMID: 30581023 DOI: 10.1016/j.cub.2018.11.045] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2018] [Revised: 10/12/2018] [Accepted: 11/16/2018] [Indexed: 10/27/2022]
Abstract
Cell adhesion, morphogenesis, mechanosensing, and muscle contraction rely on contractile actomyosin bundles, where the force is produced through sliding of bipolar myosin II filaments along actin filaments. The assembly of contractile actomyosin bundles involves registered alignment of myosin II filaments and their subsequent fusion into large stacks. However, mechanisms underlying the assembly of myosin II stacks and their physiological functions have remained elusive. Here, we identified myosin-18B, an unconventional myosin, as a stable component of contractile stress fibers. Myosin-18B co-localized with myosin II motor domains in stress fibers and was enriched at the ends of myosin II stacks. Importantly, myosin-18B deletion resulted in drastic defects in the concatenation and persistent association of myosin II filaments with each other and thus led to severely impaired assembly of myosin II stacks. Consequently, lack of myosin-18B resulted in defective maturation of actomyosin bundles from their precursors in osteosarcoma cells. Moreover, myosin-18B knockout cells displayed abnormal morphogenesis, migration, and ability to exert forces to the environment. These results reveal a critical role for myosin-18B in myosin II stack assembly and provide evidence that myosin II stacks are important for a variety of vital processes in cells.
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Affiliation(s)
- Yaming Jiu
- Institute of Biotechnology, P.O. Box 56, University of Helsinki, 00014 Helsinki, Finland; CAS Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Chinese Academy of Sciences, Shanghai, China; University of Chinese Academy of Sciences, Beijing, China.
| | - Reena Kumari
- Institute of Biotechnology, P.O. Box 56, University of Helsinki, 00014 Helsinki, Finland
| | - Aidan M Fenix
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Niccole Schaible
- Department of Emergency Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA
| | - Xiaonan Liu
- Institute of Biotechnology, P.O. Box 56, University of Helsinki, 00014 Helsinki, Finland
| | - Markku Varjosalo
- Institute of Biotechnology, P.O. Box 56, University of Helsinki, 00014 Helsinki, Finland
| | - Ramaswamy Krishnan
- Department of Emergency Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA
| | - Dylan T Burnette
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Pekka Lappalainen
- Institute of Biotechnology, P.O. Box 56, University of Helsinki, 00014 Helsinki, Finland.
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19
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Zhang Z, Zhu J, Huang Y, Li W, Cheng H. MYO18B promotes hepatocellular carcinoma progression by activating PI3K/AKT/mTOR signaling pathway. Diagn Pathol 2018; 13:85. [PMID: 30390677 PMCID: PMC6215340 DOI: 10.1186/s13000-018-0763-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2018] [Accepted: 10/16/2018] [Indexed: 02/08/2023] Open
Abstract
BACKGROUND MYO18B has been identified as a novel tumor suppressor gene in several cancers. However, its specific roles in the progression of hepatocellular carcinoma (HCC) has not been well defined. METHODS We firstly identified the expression and prognostic values of MYO18B in HCC using TCGA cohort and our clinical data. Then, MYO18B knockdown by RNA inference was implemented to investigate the effects of MYO18B on HCC cells. Quantitative RT-PCR and Western blot were used to determine gene and protein expression levels. CCK-8 and colony formation assays were performed to examine cell proliferation capacity. Wound healing and transwell assays were used to evaluate the migration and invasion of HepG2 cells. RESULTS MYO18B was overexpressed and correlated with poor prognosis in HCC. MYO18B expression was an independent risk factor for overall survival. Knockdown of MYO18B significantly inhibited the proliferation, migration and invasion of HepG2 cells. Meanwhile, MYO18B knockdown could effectively suppress the phosphorylation of PI3K, AKT, mTOR and P70S6K, suggesting that MYO18B might promote HCC progression by targeting PI3K/AKT/mTOR signaling pathway. CONCLUSIONS MYO18B promoted tumor growth and migration via the activation of PI3K/AKT/mTOR signaling pathway. MYO18B might be a promising target for clinical intervention of HCC.
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Affiliation(s)
- Zhenyu Zhang
- Department of Traditional Chinese Medicine, Shenzhen Pingshan District People’s Hospital, Shenzhen, China
| | - Jinfeng Zhu
- Department of Traditional Chinese Medicine, Nantong Hospital of Traditional Chinese Medicine, Nantong, China
| | - Yansong Huang
- Department of Infectious Diseases, The Second Affiliated Hospital of Shantou University Medical College, NO. 69 Dongxia North Road, Shantou, 515041 People’s Republic of China
| | - Weibing Li
- Department of Infectious Diseases, The Second Affiliated Hospital of Shantou University Medical College, NO. 69 Dongxia North Road, Shantou, 515041 People’s Republic of China
| | - Hongqiu Cheng
- Department of Infectious Diseases, The Second Affiliated Hospital of Shantou University Medical College, NO. 69 Dongxia North Road, Shantou, 515041 People’s Republic of China
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20
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Cutler AA, Jackson JB, Corbett AH, Pavlath GK. Non-equivalence of nuclear import among nuclei in multinucleated skeletal muscle cells. J Cell Sci 2018; 131:jcs.207670. [PMID: 29361530 DOI: 10.1242/jcs.207670] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2017] [Accepted: 12/21/2017] [Indexed: 01/01/2023] Open
Abstract
Skeletal muscle is primarily composed of large myofibers containing thousands of post-mitotic nuclei distributed throughout a common cytoplasm. Protein production and localization in specialized myofiber regions is crucial for muscle function. Myonuclei differ in transcriptional activity and protein accumulation, but how these differences among nuclei sharing a cytoplasm are achieved is unknown. Regulated nuclear import of proteins is one potential mechanism for regulating transcription spatially and temporally in individual myonuclei. The best-characterized nuclear localization signal (NLS) in proteins is the classical NLS (cNLS), but many other NLS motifs exist. We examined cNLS and non-cNLS reporter protein import using multinucleated muscle cells generated in vitro, revealing that cNLS and non-cNLS nuclear import differs among nuclei in the same cell. Investigation of cNLS nuclear import rates in isolated myofibers ex vivo confirmed differences in nuclear import rates among myonuclei. Analyzing nuclear import throughout myogenesis revealed that cNLS and non-cNLS import varies during differentiation. Taken together, our results suggest that both spatial and temporal regulation of nuclear import pathways are important in muscle cell differentiation and protein regionalization in myofibers.
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Affiliation(s)
- Alicia A Cutler
- Department of Pharmacology, Emory University, Atlanta, GA 30322, USA.,Graduate Program in Biochemistry, Cell and Developmental Biology, Emory University, Atlanta, GA 30322, USA
| | | | - Anita H Corbett
- Department of Biology, Emory University, Atlanta, GA 30322, USA
| | - Grace K Pavlath
- Department of Pharmacology, Emory University, Atlanta, GA 30322, USA
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21
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Li YR, Yang WX. Myosins as fundamental components during tumorigenesis: diverse and indispensable. Oncotarget 2018; 7:46785-46812. [PMID: 27121062 PMCID: PMC5216836 DOI: 10.18632/oncotarget.8800] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2016] [Accepted: 04/10/2016] [Indexed: 12/11/2022] Open
Abstract
Myosin is a kind of actin-based motor protein. As the crucial functions of myosin during tumorigenesis have become increasingly apparent, the profile of myosin in the field of cancer research has also been growing. Eighteen distinct classes of myosins have been discovered in the past twenty years and constitute a diverse superfamily. Various myosins share similar structures. They all convert energy from ATP hydrolysis to exert mechanical stress upon interactions with microfilaments. Ongoing research is increasingly suggesting that at least seven kinds of myosins participate in the formation and development of cancer. Myosins play essential roles in cytokinesis failure, chromosomal and centrosomal amplification, multipolar spindle formation and DNA microsatellite instability. These are all prerequisites of tumor formation. Subsequently, myosins activate various processes of tumor invasion and metastasis development including cell migration, adhesion, protrusion formation, loss of cell polarity and suppression of apoptosis. In this review, we summarize the current understanding of the roles of myosins during tumorigenesis and discuss the factors and mechanisms which may regulate myosins in tumor progression. Furthermore, we put forward a completely new concept of “chromomyosin” to demonstrate the pivotal functions of myosins during karyokinesis and how this acts to optimize the functions of the members of the myosin superfamily.
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Affiliation(s)
- Yan-Ruide Li
- The Sperm Laboratory, College of Life Sciences, Zhejiang University, Hangzhou, China
| | - Wan-Xi Yang
- The Sperm Laboratory, College of Life Sciences, Zhejiang University, Hangzhou, China
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22
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Majewski L, Nowak J, Sobczak M, Karatsai O, Havrylov S, Lenartowski R, Suszek M, Lenartowska M, Redowicz MJ. Myosin VI in the nucleus of neurosecretory PC12 cells: Stimulation-dependent nuclear translocation and interaction with nuclear proteins. Nucleus 2018; 9:125-141. [PMID: 29293066 PMCID: PMC5973263 DOI: 10.1080/19491034.2017.1421881] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2017] [Revised: 11/23/2017] [Accepted: 12/18/2017] [Indexed: 02/07/2023] Open
Abstract
Myosin VI (MVI) is a unique actin-based motor protein moving towards the minus end of actin filaments, in the opposite direction than other known myosins. Besides well described functions of MVI in endocytosis and maintenance of Golgi apparatus, there are few reports showing its involvement in transcription. We previously demonstrated that in neurosecretory PC12 cells MVI was present in the cytoplasm and nucleus, and its depletion caused substantial inhibition of cell migration and proliferation. Here, we show an increase in nuclear localization of MVI upon cell stimulation, and identification of potential nuclear localization (NLS) and nuclear export (NES) signals within MVI heavy chain. These signals seem to be functional as the MVI nuclear presence was affected by the inhibitors of nuclear import (ivermectin) and export (leptomycin B). In nuclei of stimulated cells, MVI colocalized with active RNA polymerase II, BrUTP-containing transcription sites and transcription factor SP1 as well as SC35 and PML proteins, markers of nuclear speckles and PML bodies, respectively. Mass spectrometry analysis of samples of a GST-pull-down assay with the MVI tail domain as a "bait" identified several new potential MVI binding partners. Among them are proteins involved in transcription and post-transcriptional processes. We confirmed interaction of MVI with heterogeneous nuclear ribonucleoprotein U (hnRNPU) and nucleolin, proteins involved in pre-mRNA binding and transport, and nucleolar function, respectively. Our data provide an insight into mechanisms of involvement of MVI in nuclear processes via interaction with nuclear proteins and support a notion for important role(s) for MVI in gene expression.
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Affiliation(s)
- Lukasz Majewski
- Laboratory of Molecular Basis of Cell Motility, Department of Biochemistry, Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warsaw, Poland
| | - Jolanta Nowak
- Laboratory of Molecular Basis of Cell Motility, Department of Biochemistry, Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warsaw, Poland
| | - Magdalena Sobczak
- Laboratory of Molecular Basis of Cell Motility, Department of Biochemistry, Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warsaw, Poland
| | - Olena Karatsai
- Laboratory of Molecular Basis of Cell Motility, Department of Biochemistry, Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warsaw, Poland
| | - Serhiy Havrylov
- Laboratory of Molecular Basis of Cell Motility, Department of Biochemistry, Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warsaw, Poland
| | - Robert Lenartowski
- Laboratory of Isotope and Instrumental Analysis, Department of Cellular and Molecular Biology, Faculty of Biology and Environmental Protection, Nicolaus Copernicus University in Torun, Torun, Poland
| | - Malgorzata Suszek
- Laboratory of Molecular Basis of Cell Motility, Department of Biochemistry, Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warsaw, Poland
| | - Marta Lenartowska
- Laboratory of Developmental Biology, Department of Cellular and Molecular Biology, Faculty of Biology and Environmental Protection, Nicolaus Copernicus University in Torun, Torun, Poland
| | - Maria Jolanta Redowicz
- Laboratory of Molecular Basis of Cell Motility, Department of Biochemistry, Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warsaw, Poland
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23
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Differences in bone structure and unloading-induced bone loss between C57BL/6N and C57BL/6J mice. Mamm Genome 2017; 28:476-486. [PMID: 28913652 DOI: 10.1007/s00335-017-9717-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2017] [Accepted: 09/06/2017] [Indexed: 12/24/2022]
Abstract
The C57BL/6 mouse, the most frequently utilized animal model in biomedical research, is in use as several substrains, all of which differ by a small array of genomic differences. Two of these substrains, C57BL/6J (B6J) and C57BL/6N (B6N), are commonly used but it is unclear how phenotypically similar or different they are. Here, we tested whether adolescent B6N mice have a bone phenotype and respond to the loss of weightbearing differently than B6J. At 9 weeks of age, normally ambulating B6N had lower trabecular bone volume fraction but greater bone formation rates and osteoblast surfaces than corresponding B6J. At 11 weeks of age, differences in trabecular indices persisted between the substrains but differences in cellular activity had ceased. Cortical bone indices were largely similar between the two substrains. Hindlimb unloading (HLU) induced similar degeneration of trabecular architecture and cellular activity in both substrains when comparing 11-week-old HLU mice to 11-week-old controls. However, unloaded B6N mice had smaller cortices than B6J. When comparing HLU to 9 weeks baseline control mice, deterioration in trabecular separation, osteoblast indices, and endocortical variables was significantly greater in B6N than B6J. These data indicate specific developmental differences in bone formation and morphology between B6N and B6J mice, giving rise to a differential response to mechanical unloading that may be modulated, in part, by the genes Herc2, Myo18b, and Acan. Our results emphasize that these substrains cannot be used interchangeably at least for investigations in which the phenotypic makeup and its response to extraneous stimuli are of interest.
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24
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How myosin organization of the actin cytoskeleton contributes to the cancer phenotype. Biochem Soc Trans 2017; 44:1026-34. [PMID: 27528748 DOI: 10.1042/bst20160034] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2016] [Indexed: 12/29/2022]
Abstract
The human genome contains 39 genes that encode myosin heavy chains, classified on the basis of their sequence similarity into 12 classes. Most cells express at least 12 different genes, from at least 8 different classes, which are typically composed of several class 1 genes, at least one class 2 gene and classes 5, 6, 9, 10, 18 and 19. Although the different myosin isoforms all have specific and non-overlapping roles in the cell, in combination they all contribute to the organization of the actin cytoskeleton, and the shape and phenotype of the cell. Over (or under) expression of these different myosin isoforms can have strong effects on actin organization, cell shape and contribute to the cancer phenotype as discussed in this review.
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25
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Abstract
Gene amplifications are mostly an attribute of tumor cells and drug resistant cells. Recently, we provided evidence for gene amplifications during differentiation of human and mouse neural progenitor cells. Here, we report gene amplifications in differentiating mouse myoblasts (C2C12 cells) covering a period of 7 days including pre-fusion, fusion and post-fusion stages. After differentiation induction we found an increase in copy numbers of CDK4 gene at day 3, of NUP133 at days 4 and 7, and of MYO18B at day 4. The amplification process was accompanied by gamma-H2AX foci that are indicative of double stand breaks. Amplifications during the differentiating process were also found in primary human myoblasts with the gene CDK4 and NUP133 amplified both in human and mouse myoblasts. Amplifications of NUP133 and CDK4 were also identified in vivo on mouse transversal cryosections at stage E11.5. In the course of myoblast differentiation, we found amplifications in cytoplasm indicative of removal of amplified sequences from the nucleus. The data provide further evidence that amplification is a fundamental mechanism contributing to the differentiation process in mammalians.
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26
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Masters TA, Kendrick-Jones J, Buss F. Myosins: Domain Organisation, Motor Properties, Physiological Roles and Cellular Functions. Handb Exp Pharmacol 2017; 235:77-122. [PMID: 27757761 DOI: 10.1007/164_2016_29] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Myosins are cytoskeletal motor proteins that use energy derived from ATP hydrolysis to generate force and movement along actin filaments. Humans express 38 myosin genes belonging to 12 classes that participate in a diverse range of crucial activities, including muscle contraction, intracellular trafficking, cell division, motility, actin cytoskeletal organisation and cell signalling. Myosin malfunction has been implicated a variety of disorders including deafness, hypertrophic cardiomyopathy, Usher syndrome, Griscelli syndrome and cancer. In this chapter, we will first discuss the key structural and kinetic features that are conserved across the myosin family. Thereafter, we summarise for each member in turn its unique functional and structural adaptations, cellular roles and associated pathologies. Finally, we address the broad therapeutic potential for pharmacological interventions that target myosin family members.
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Affiliation(s)
- Thomas A Masters
- 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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27
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A Zebrafish Model for a Human Myopathy Associated with Mutation of the Unconventional Myosin MYO18B. Genetics 2016; 205:725-735. [PMID: 27879346 DOI: 10.1534/genetics.116.192864] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2016] [Accepted: 11/18/2016] [Indexed: 02/04/2023] Open
Abstract
Myosin 18B is an unconventional myosin that has been implicated in tumor progression in humans. In addition, loss-of-function mutations of the MYO18B gene have recently been identified in several patients exhibiting symptoms of nemaline myopathy. In mouse, mutation of Myo18B results in early developmental arrest associated with cardiomyopathy, precluding analysis of its effects on skeletal muscle development. The zebrafish, frozen (fro) mutant was identified as one of a group of immotile mutants in the 1996 Tübingen genetic screen. Mutant embryos display a loss of birefringency in their skeletal muscle, indicative of disrupted sarcomeric organization. Using meiotic mapping, we localized the fro locus to the previously unannotated zebrafish myo18b gene, the product of which shares close to 50% identity with its human ortholog. Transcription of myo18b is restricted to fast-twitch myocytes in the zebrafish embryo; consistent with this, fro mutant embryos exhibit defects specifically in their fast-twitch skeletal muscles. We show that sarcomeric assembly is blocked at an early stage in fro mutants, leading to the disorganized accumulation of actin, myosin, and α-actinin and a complete loss of myofibrillar organization in fast-twitch muscles.
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28
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Malfatti E, Böhm J, Lacène E, Beuvin M, Romero NB, Laporte J. A Premature Stop Codon in MYO18B is Associated with Severe Nemaline Myopathy with Cardiomyopathy. J Neuromuscul Dis 2015; 2:219-227. [PMID: 27858739 PMCID: PMC5240573 DOI: 10.3233/jnd-150085] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Background: Nemaline myopathies (NM) are rare and severe muscle diseases characterized by the presence of nemaline bodies (rods) in muscle fibers. Although ten genes have been implicated in the etiology of NM, an important number of patients remain without a molecular diagnosis. Objective: Here we describe the clinical and histopathological features of a sporadic case presenting with severe NM and cardiomyopathy. Using exome sequencing, we aimed to identify the causative gene. Results: We identified a homozygous nonsense mutation in the last exon of MYO18B, leading to a truncated protein lacking the most C-terminal part. MYO18B codes for an unconventional myosin protein and it is mainly expressed in skeletal and cardiac muscles, two tissues severely affected in the patient. We showed that the mutation does not impact on mRNA stability. Immunostaining and Western blot confirmed the absence of the full-length protein. Conclusion: We propose MYO18B as a novel gene associated with nemaline myopathy and cardiomyopathy.
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Affiliation(s)
- Edoardo Malfatti
- Sorbonne Universités, UPMC Univ Paris 06, INSERM UMRS974, CNRS FRE3617, Center for Research in Myology, GH Pitié-Salpêtrière, 47 Boulevard de l'hôpital, 75013 Paris, France.,Unité de Morphologie Neuromusculaire, Institut de Myologie, Groupe Hospitalier Universitaire La Pitié-Salpêtrière; Paris, France
| | - Johann Böhm
- Department of Translational Medecine, IGBMC, Illkirch, France.,INSERM U964, Illkirch, France.,CNRS, UMR7104, Illkirch, France.,Strasbourg University, Illkirch, France
| | - Emmanuelle Lacène
- Sorbonne Universités, UPMC Univ Paris 06, INSERM UMRS974, CNRS FRE3617, Center for Research in Myology, GH Pitié-Salpêtrière, 47 Boulevard de l'hôpital, 75013 Paris, France.,Unité de Morphologie Neuromusculaire, Institut de Myologie, Groupe Hospitalier Universitaire La Pitié-Salpêtrière; Paris, France.,Centre de référence de Pathologie Neuromusculaire Paris-Est, Institut de Myologie, GHU La Pitié-Salpêtrière, Assistance Publique-Hôpitaux de Paris; Paris, France
| | - Maud Beuvin
- Sorbonne Universités, UPMC Univ Paris 06, INSERM UMRS974, CNRS FRE3617, Center for Research in Myology, GH Pitié-Salpêtrière, 47 Boulevard de l'hôpital, 75013 Paris, France.,Unité de Morphologie Neuromusculaire, Institut de Myologie, Groupe Hospitalier Universitaire La Pitié-Salpêtrière; Paris, France
| | - Norma B Romero
- Sorbonne Universités, UPMC Univ Paris 06, INSERM UMRS974, CNRS FRE3617, Center for Research in Myology, GH Pitié-Salpêtrière, 47 Boulevard de l'hôpital, 75013 Paris, France.,Unité de Morphologie Neuromusculaire, Institut de Myologie, Groupe Hospitalier Universitaire La Pitié-Salpêtrière; Paris, France.,Centre de référence de Pathologie Neuromusculaire Paris-Est, Institut de Myologie, GHU La Pitié-Salpêtrière, Assistance Publique-Hôpitaux de Paris; Paris, France
| | - Jocelyn Laporte
- Department of Translational Medecine, IGBMC, Illkirch, France.,INSERM U964, Illkirch, France.,CNRS, UMR7104, Illkirch, France.,Strasbourg University, Illkirch, France
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Karolczak J, Weis S, Ehler E, Kierdaszuk B, Berdyński M, Zekanowski C, Kamińska AM, Rędowicz MJ. Myosin VI localization and expression in striated muscle pathology. Anat Rec (Hoboken) 2015; 297:1706-13. [PMID: 25125183 DOI: 10.1002/ar.22967] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2013] [Accepted: 02/04/2014] [Indexed: 12/11/2022]
Abstract
Myosin VI (MVI) is a unique unconventional myosin translocating, unlike other myosins, towards the minus end of actin filaments. It is involved in numerous cellular processes such as endocytosis, intracellular trafficking, cell migration, and transcription. In mammalian skeletal muscles it localizes mainly to sarcoplasmic reticulum and is also present within the muscle nuclei and at the neuromuscular junction (Karolczak et al. Histochem Cell Biol 2013; 23:219-228). We have also shown that in denervated rat hindlimb muscle the MVI expression level is significantly increased and its localization is changed, indicating an important role of MVI in striated muscle pathology. Here, we addressed this problem by examining the distribution and expression levels of myosin VI in biopsies of skeletal muscles from patients with different myopathies. We found that, particularly in myopathies associated with fiber atrophy, the amount of MVI was enhanced and its localization in affected fibers was changed. Also, since a mutation within the human MVI gene was shown to be associated with cardiomyopathy, we assessed MVI localization and expression level in cardiac muscle using wild type and MLP(-/-) mice, a dilated cardiomyopathy model. No significant difference in MVI expression level was observed for both types of animals. MVI was found at intercalated discs and also at the sarcoplasmic reticulum. In the knockout mice, it was also present in ring-like structures surrounding the nuclei. The data indicate that in striated muscle MVI could be engaged in sarcoplasmic reticulum maintenance and/or functioning, vesicular transport, signal transmission and possibly in gene transcription.
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Affiliation(s)
- Justyna Karolczak
- Department of Biochemistry, Laboratory of Molecular Basis of Cell Motility, Nencki Institute of Experimental Biology, Warsaw, Poland
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Involvement of unconventional myosin VI in myoblast function and myotube formation. Histochem Cell Biol 2015; 144:21-38. [PMID: 25896210 PMCID: PMC4469105 DOI: 10.1007/s00418-015-1322-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/07/2015] [Indexed: 01/01/2023]
Abstract
The important role of unconventional myosin VI (MVI) in skeletal and cardiac muscle has been recently postulated (Karolczak et al. in Histochem Cell Biol 139:873-885, 2013). Here, we addressed for the first time a role for this unique myosin motor in myogenic cells as well as during their differentiation into myotubes. During myoblast differentiation, the isoform expression pattern of MVI and its subcellular localization underwent changes. In undifferentiated myoblasts, MVI-stained puncti were seen throughout the cytoplasm and were in close proximity to actin filaments, Golgi apparatus, vinculin-, and talin-rich focal adhesion as well as endoplasmic reticulum. Colocalization of MVI with endoplasmic reticulum was enhanced during myotube formation, and differentiation-dependent association was also seen in sarcoplasmic reticulum of neonatal rat cardiomyocytes (NRCs). Moreover, we observed enrichment of MVI in myotube regions containing acetylcholine receptor-rich clusters, suggesting its involvement in the organization of the muscle postsynaptic machinery. Overexpression of the H246R MVI mutant (associated with hypertrophic cardiomyopathy) in myoblasts and NRCs caused the formation of abnormally large intracellular vesicles. MVI knockdown caused changes in myoblast morphology and inhibition of their migration. On the subcellular level, MVI-depleted myoblasts exhibited aberrations in the organization of actin cytoskeleton and adhesive structures as well as in integrity of Golgi apparatus and endoplasmic reticulum. Also, MVI depletion or overexpression of H246R mutant caused the formation of significantly wider or aberrant myotubes, respectively, indicative of involvement of MVI in myoblast differentiation. The presented results suggest an important role for MVI in myogenic cells and possibly in myoblast differentiation.
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31
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Sarshad AA, Percipalle P. New Insight into Role of Myosin Motors for Activation of RNA Polymerases. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2014; 311:183-230. [DOI: 10.1016/b978-0-12-800179-0.00004-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Abstract
In the cytoplasm, actin filaments form crosslinked networks that enable eukaryotic cells to transport cargo, change shape, and move. Actin is also present in the nucleus but, in this compartment, its functions are more cryptic and controversial. If we distill the substantial literature on nuclear actin down to its essentials, we find four, recurring, and more-or-less independent, claims: (1) crosslinked networks of conventional actin filaments span the nucleus and help maintain its structure and organize its contents; (2) assembly or contraction of filaments regulates specific nuclear events; (3) actin monomers moonlight as subunits of chromatin remodeling complexes, independent of their ability to form filaments; and (4) modified actin monomers or oligomers, structurally distinct from canonical, cytoskeletal filaments, mediate nuclear events by unknown mechanisms. We discuss the evidence underlying these claims and as well as their strengths and weaknesses. Next, we describe our recent work, in which we built probes specific for nuclear actin and used them to describe the form and distribution of actin in somatic cell nuclei. Finally, we discuss how different forms of nuclear actin may play different roles in different cell types and physiological contexts.
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Affiliation(s)
- Brittany J Belin
- Cellular and Molecular Pharmacology; University of California; San Francisco, CA USA
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33
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Affiliation(s)
- Primal de Lanerolle
- Department of Physiology and Biophysics, University of Illinois at Chicago, 835 South Wolcott Avenue, Chicago, IL 60612, USA.
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Cameron RS, Liu C, Pihkala JPS. Myosin 16 levels fluctuate during the cell cycle and are downregulated in response to DNA replication stress. Cytoskeleton (Hoboken) 2013; 70:328-48. [PMID: 23596177 DOI: 10.1002/cm.21109] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2013] [Accepted: 03/27/2013] [Indexed: 01/03/2023]
Abstract
Myosins comprise a highly conserved superfamily of eukaryotic actin-dependent motor proteins implicated in a large repertoire of functions in both the cytoplasm and the nucleus. Class XVI myosin, MYO16, reveals expression in most somatic as well as meiotic cells with prominent localization in the nucleus, excepting the nucleolus; however, the role(s) of Myo16 in the nucleus remain unknown. In this report, we investigated Myo16 abundance during transit through the cell cycle. Immunolocalization, immunoblot, flow cytometric and quantitative RT-PCR studies performed in Rat2 cells indicate that Myo16 mRNA and protein abundance are cell cycle regulated: in the unperturbed cell cycle, each rises to peak levels in late G1 and thereon through S-phase and each decays as cells enter M-phase. Notably, RNA interference-induced Myo16 depletion results in altered cell cycle distribution as well as in large-scale cell death. In response to DNA replication stress (impaired replication fork progression as a consequence of DNA damage, lack of sufficient deoxynucleotides, or inhibition of DNA polymerases), Myo16 protein shows substantial loss. Attenuation of replication stress (aphidicolin or hydroxyurea) is followed by a recovery of Myo16 expression and resumption of S-phase progression. Collectively, these observations suggest that Myo16 may play a regulatory role in cell cycle progression.
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Affiliation(s)
- Richard S Cameron
- Institute of Molecular Medicine and Genetics, Department of Medicine, Georgia Regents University, Medical College of Georgia, Augusta, Georgia 30912, USA.
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35
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Guarnieri S, Morabito C, Paolini C, Boncompagni S, Pilla R, Fanò-Illic G, Mariggiò MA. Growth associated protein 43 is expressed in skeletal muscle fibers and is localized in proximity of mitochondria and calcium release units. PLoS One 2013; 8:e53267. [PMID: 23308181 PMCID: PMC3538766 DOI: 10.1371/journal.pone.0053267] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2012] [Accepted: 11/27/2012] [Indexed: 11/26/2022] Open
Abstract
The neuronal Growth Associated Protein 43 (GAP43), also known as B-50 or neuromodulin, is involved in mechanisms controlling pathfinding and branching of neurons during development and regeneration. For many years this protein was classified as neuron-specific, but recent evidences suggest that a) GAP43 is expressed in the nervous system not only in neurons, but also in glial cells, and b) probably it is present also in other tissues. In particular, its expression was revealed in muscles from patients affected by various myopathies, indicating that GAP43 can no-longer considered only as a neuron-specific molecule. We have investigated the expression and subcellular localization of GAP43 in mouse satellite cells, myotubes, and adult muscle (extensor digitorum longus or EDL) using Western blotting, immuno-fluorescence combined to confocal microscopy and electron microscopy. Our in vitro results indicated that GAP43 is indeed expressed in both myoblasts and differentiating myotubes, and its cellular localization changes dramatically during maturation: in myoblasts the localization appeared to be mostly nuclear, whereas with differentiation the protein started to display a sarcomeric-like pattern. In adult fibers, GAP43 expression was evident with the protein labeling forming (in longitudinal views) a double cross striation reminiscent of the staining pattern of other organelles, such as calcium release units (CRUs) and mitochondria. Double immuno-staining and experiments done in EDL muscles fixed at different sarcomere lengths, allowed us to determine the localization, from the sarcomere Z-line, of GAP43 positive foci, falling between that of CRUs and of mitochondria. Staining of cross sections added a detail to the puzzle: GAP43 labeling formed a reticular pattern surrounding individual myofibrils, but excluding contractile elements. This work leads the way to further investigation about the possible physiological and structural role of GAP43 protein in adult fiber function and disease.
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Affiliation(s)
- Simone Guarnieri
- Department of Neuroscience and Imaging (DNI), University G. d’Annunzio, Chieti, Italy
- Center for Research on Ageing (CeSI), University G. d’Annunzio, Chieti, Italy
- Interuniversitary Institute of Myology (IIM), University G. d’Annunzio, Chieti, Italy
| | - Caterina Morabito
- Department of Neuroscience and Imaging (DNI), University G. d’Annunzio, Chieti, Italy
- Center for Research on Ageing (CeSI), University G. d’Annunzio, Chieti, Italy
- Interuniversitary Institute of Myology (IIM), University G. d’Annunzio, Chieti, Italy
| | - Cecilia Paolini
- Department of Neuroscience and Imaging (DNI), University G. d’Annunzio, Chieti, Italy
- Center for Research on Ageing (CeSI), University G. d’Annunzio, Chieti, Italy
- Interuniversitary Institute of Myology (IIM), University G. d’Annunzio, Chieti, Italy
| | - Simona Boncompagni
- Department of Neuroscience and Imaging (DNI), University G. d’Annunzio, Chieti, Italy
- Center for Research on Ageing (CeSI), University G. d’Annunzio, Chieti, Italy
- Interuniversitary Institute of Myology (IIM), University G. d’Annunzio, Chieti, Italy
| | - Raffaele Pilla
- Center for Research on Ageing (CeSI), University G. d’Annunzio, Chieti, Italy
- Interuniversitary Institute of Myology (IIM), University G. d’Annunzio, Chieti, Italy
| | - Giorgio Fanò-Illic
- Department of Neuroscience and Imaging (DNI), University G. d’Annunzio, Chieti, Italy
- Center for Research on Ageing (CeSI), University G. d’Annunzio, Chieti, Italy
- Interuniversitary Institute of Myology (IIM), University G. d’Annunzio, Chieti, Italy
| | - Maria A. Mariggiò
- Department of Neuroscience and Imaging (DNI), University G. d’Annunzio, Chieti, Italy
- Center for Research on Ageing (CeSI), University G. d’Annunzio, Chieti, Italy
- Interuniversitary Institute of Myology (IIM), University G. d’Annunzio, Chieti, Italy
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36
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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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37
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Bonn BR, Rudolf A, Hornbruch-Freitag C, Daum G, Kuckwa J, Kastl L, Buttgereit D, Renkawitz-Pohl R. Myosin heavy chain-like localizes at cell contact sites during Drosophila myoblast fusion and interacts in vitro with Rolling pebbles 7. Exp Cell Res 2012; 319:402-16. [PMID: 23246571 DOI: 10.1016/j.yexcr.2012.12.005] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2011] [Revised: 12/04/2012] [Accepted: 12/05/2012] [Indexed: 11/29/2022]
Abstract
Besides representing the sarcomeric thick filaments, myosins are involved in many cellular transport and motility processes. Myosin heavy chains are grouped into 18 classes. Here we show that in Drosophila, the unconventional group XVIII myosin heavy chain-like (Mhcl) is transcribed in the mesoderm of embryos, most prominently in founder cells (FCs). An ectopically expressed GFP-tagged Mhcl localizes in the growing muscle at cell-cell contacts towards the attached fusion competent myoblast (FCM). We further show that Mhcl interacts in vitro with the essential fusion protein Rolling pebbles 7 (Rols7), which is part of a protein complex established at cell contact sites (Fusion-restricted Myogenic-Adhesive Structure or FuRMAS). Here, branched F-actin is likely needed to widen the fusion pore and to integrate the myoblast into the growing muscle. We show that the localization of Mhcl is dependent on the presence of Rols7, and we postulate that Mhcl acts at the FuRMAS as an actin motor protein. We further show that Mhcl deficient embryos develop a wild-type musculature. We thus propose that Mhcl functions redundantly to other myosin heavy chains in myoblasts. Lastly, we found that the protein is detectable adjacent to the sarcomeric Z-discs, suggesting an additional function in mature muscles.
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Affiliation(s)
- Bettina R Bonn
- Developmental Biology, Department of Biology, Philipps-Universität Marburg, Karl-von-Frisch-Strasse 8, 35037 Marburg, Germany
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38
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Abstract
Actin is a key player for nuclear structure and function regulating both chromosome organization and gene activity. In the cell nucleus actin interacts with many different proteins. Among these proteins several studies have identified classical nuclear factors involved in chromatin structure and function, transcription and RNA processing as well as proteins that are normally involved in controlling the actin cytoskeleton. These discoveries have raised the possibility that nuclear actin performs its multi task activities through tight interactions with different sets of proteins. This high degree of promiscuity in the spectrum of protein-to-protein interactions correlates well with the conformational plasticity of actin and the ability to undergo regulated changes in its polymerization states. Several of the factors involved in controlling head-to-tail actin polymerization have been shown to be in the nucleus where they seem to regulate gene activity. By focusing on the multiple tasks performed by actin and actin-binding proteins, possible models of how actin dynamics controls the different phases of the RNA polymerase II transcription cycle are being identified.
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39
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Ihnatovych I, Migocka-Patrzalek M, Dukh M, Hofmann WA. Identification and characterization of a novel myosin Ic isoform that localizes to the nucleus. Cytoskeleton (Hoboken) 2012; 69:555-65. [PMID: 22736583 DOI: 10.1002/cm.21040] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2012] [Revised: 05/07/2012] [Accepted: 05/09/2012] [Indexed: 11/05/2022]
Abstract
In vertebrates, two myosin Ic isoforms that localize to the cytoplasm and to the nucleus have been characterized. The isoform that predominantly localizes to the nucleus is called nuclear myosin I (NMI). NMI has been identified as a key factor involved in nuclear processes such as transcription by RNA polymerases I and II and intranuclear transport processes. We report here the identification of a previously uncharacterized third MYOIC gene product that is called isoform A. Similar to NMI, this isoform contains a unique N-terminal peptide sequence, localizes to the nucleus and colocalizes with RNA polymerase II. However, unlike NMI, upon exposure to inhibitors of RNA polymerase II transcription the newly identified isoform translocates to nuclear speckles. Furthermore, in contrast to NMI, this new isoform is absent from nucleoli and does not colocalize with RNA polymerase I. Our results suggest an unexpected diversity among nuclear myosin Ic isoforms in respect to their intranuclear localization and interaction with nuclear binding partners that could provide new insights into the regulation of myosin-dependent nuclear processes.
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Affiliation(s)
- Ivanna Ihnatovych
- Department of Physiology and Biophysics, University at Buffalo-State University of New York, Buffalo, New York 14214, USA
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40
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Doherty TA, Khorram N, Sugimoto K, Sheppard D, Rosenthal P, Cho JY, Pham A, Miller M, Croft M, Broide DH. Alternaria induces STAT6-dependent acute airway eosinophilia and epithelial FIZZ1 expression that promotes airway fibrosis and epithelial thickness. THE JOURNAL OF IMMUNOLOGY 2012; 188:2622-9. [PMID: 22327070 DOI: 10.4049/jimmunol.1101632] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
The fungal allergen, Alternaria, is specifically associated with severe asthma, including life-threatening exacerbations. To better understand the acute innate airway response to Alternaria, naive wild-type (WT) mice were challenged once intranasally with Alternaria. Naive WT mice developed significant bronchoalveolar lavage eosinophilia following Alternaria challenge when analyzed 24 h later. In contrast to Alternaria, neither Aspergillus nor Candida induced bronchoalveolar lavage eosinophilia. Gene microarray analysis of airway epithelial cell brushings demonstrated that Alternaria-challenged naive WT mice had a >20-fold increase in the level of expression of found in inflammatory zone 1 (FIZZ1/Retnla), a resistin-like molecule. Lung immunostaining confirmed strong airway epithelial FIZZ1 expression as early as 3 h after a single Alternaria challenge that persisted for ≥5 d and was significantly reduced in STAT6-deficient, but not protease-activated receptor 2-deficient mice. Bone marrow chimera studies revealed that STAT6 expressed in lung cells was required for epithelial FIZZ1 expression, whereas STAT6 present in bone marrow-derived cells contributed to airway eosinophilia. Studies investigating which cells in the nonchallenged lung bind FIZZ1 demonstrated that CD45(+)CD11c(+) cells (macrophages and dendritic cells), as well as collagen-1-producing CD45(-) cells (fibroblasts), can bind to FIZZ1. Importantly, direct administration of recombinant FIZZ1 to naive WT mice led to airway eosinophilia, peribronchial fibrosis, and increased thickness of the airway epithelium. Thus, Alternaria induces STAT6-dependent acute airway eosinophilia and epithelial FIZZ1 expression that promotes airway fibrosis and epithelial thickness. This may provide some insight into the uniquely pathogenic aspects of Alternaria-associated asthma.
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Affiliation(s)
- Taylor A Doherty
- Department of Medicine, University of California San Diego, La Jolla, CA 92093-0635, USA.
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41
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Abstract
The evolution of the nucleus, the defining feature of eukaryotic cells, was long shrouded in speculation and mystery. There is now strong evidence that nuclear pore complexes (NPCs) and nuclear membranes coevolved with the endomembrane system, and that the last eukaryotic common ancestor (LECA) had fully functional NPCs. Recent studies have identified many components of the nuclear envelope in living Opisthokonts, the eukaryotic supergroup that includes fungi and metazoan animals. These components include diverse chromatin-binding membrane proteins, and membrane proteins with adhesive lumenal domains that may have contributed to the evolution of nuclear membrane architecture. Further discoveries about the nucleoskeleton suggest that the evolution of nuclear structure was tightly coupled to genome partitioning during mitosis.
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Affiliation(s)
- Katherine L Wilson
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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42
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de Lanerolle P, Serebryannyy L. Nuclear actin and myosins: life without filaments. Nat Cell Biol 2011; 13:1282-8. [PMID: 22048410 DOI: 10.1038/ncb2364] [Citation(s) in RCA: 117] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Actin and myosin are major components of the cell cytoskeleton, with structural and regulatory functions that affect many essential cellular processes. Although they were traditionally thought to function only in the cytoplasm, it is now well accepted that actin and multiple myosins are found in the nucleus. Increasing evidence on their functional roles has highlighted the importance of these proteins in the nuclear compartment.
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Affiliation(s)
- Primal de Lanerolle
- Department of Physiology and Biophysics, University of Illinois at Chicago, Chicago, Illinois 60612, USA.
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43
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Simon DN, Wilson KL. The nucleoskeleton as a genome-associated dynamic 'network of networks'. Nat Rev Mol Cell Biol 2011; 12:695-708. [PMID: 21971041 DOI: 10.1038/nrm3207] [Citation(s) in RCA: 219] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
In the cytosol, actin polymers, intermediate filaments and microtubules can anchor to cell surface adhesions and interlink to form intricate networks. This cytoskeleton is anchored to the nucleus through LINC (links the nucleoskeleton and cytoskeleton) complexes that span the nuclear envelope and in turn anchor to networks of filaments in the nucleus. The metazoan nucleoskeleton includes nuclear pore-linked filaments, A-type and B-type lamin intermediate filaments, nuclear mitotic apparatus (NuMA) networks, spectrins, titin, 'unconventional' polymers of actin and at least ten different myosin and kinesin motors. These elements constitute a poorly understood 'network of networks' that dynamically reorganizes during mitosis and is responsible for genome organization and integrity.
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Affiliation(s)
- Dan N Simon
- Department of Cell Biology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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44
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Park SK, Jeon YM, Son BS, Youn HS, Lee MY. Proteomic analysis of the differentially expressed proteins by airborne nanoparticles. J Appl Toxicol 2011; 31:463-70. [PMID: 21491466 DOI: 10.1002/jat.1658] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2010] [Accepted: 12/23/2010] [Indexed: 12/12/2022]
Abstract
Airborne nanoparticles with thermodynamic diameters less than 56 nm (PM(0.056)) were collected using a Moudi cascade impactor, and the differentially expressed proteins upon exposure to the airborne nanoparticles were identified in human bronchial epithelial cells. More than 600 protein spots were detected on the two-dimensional gel, and the identified 13 of these proteins showed notable changes. Nine were up-regulated and four were down-regulated following treatment with the airborne nanoparticles. Notably, malignant transformation-associated multiple forms of keratins, epigenetic regulation-related MBD1-containing chromatin associated factor 2, epithelial malignancy-related vimentin and exocytosis-related annexin A2 were changed upon exposure to airborne nanoparticle PM(0.056).
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Affiliation(s)
- Seul Ki Park
- Department of Medical Biotechnology, SoonChunHyang University, Asan, Chungnam, 336-600, Republic of Korea
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45
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Hall MN, Corbett AH, Pavlath GK. Regulation of nucleocytoplasmic transport in skeletal muscle. Curr Top Dev Biol 2011; 96:273-302. [PMID: 21621074 DOI: 10.1016/b978-0-12-385940-2.00010-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Proper skeletal muscle function is dependent on spatial and temporal control of gene expression in multinucleated myofibers. In addition, satellite cells, which are tissue-specific stem cells that contribute critically to repair and maintenance of skeletal muscle, are also required for normal muscle physiology. Gene expression in both myofibers and satellite cells is dependent upon nuclear proteins that require facilitated nuclear transport. A unique challenge for myofibers is controlling the transcriptional activity of hundreds of nuclei in a common cytoplasm yet achieving nuclear selectivity in transcription at specific locations such as neuromuscular synapses and myotendinous junctions. Nucleocytoplasmic transport of macromolecular cargoes is regulated by a complex interplay among various components of the nuclear transport machinery, namely nuclear pore complexes, nuclear envelope proteins, and various soluble transport receptors. The focus of this review is to highlight what is known about the nuclear transport machinery and its regulation in skeletal muscle and to consider the unique challenges that multinucleated muscle cells as well as satellite cells encounter in regulating nucleocytoplasmic transport during cell differentiation and tissue adaptation. Understanding how regulated nucleocytoplasmic transport controls gene expression in skeletal muscle may lead to further insights into the mechanisms contributing to muscle growth and maintenance throughout the lifespan of an individual.
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Affiliation(s)
- Monica N Hall
- Graduate Program in Genetics and Molecular Biology, Emory University, Atlanta, Georgia, USA
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46
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Castano E, Philimonenko VV, Kahle M, Fukalová J, Kalendová A, Yildirim S, Dzijak R, Dingová-Krásna H, Hozák P. Actin complexes in the cell nucleus: new stones in an old field. Histochem Cell Biol 2010; 133:607-26. [PMID: 20443021 DOI: 10.1007/s00418-010-0701-2] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/12/2010] [Indexed: 01/13/2023]
Abstract
Actin is a well-known protein that has shown a myriad of activities in the cytoplasm. However, recent findings of actin involvement in nuclear processes are overwhelming. Actin complexes in the nucleus range from very dynamic chromatin-remodeling complexes to structural elements of the matrix with single partners known as actin-binding proteins (ABPs). This review summarizes the recent findings of actin-containing complexes in the nucleus. Particular attention is given to key processes like chromatin remodeling, transcription, DNA replication, nucleocytoplasmic transport and to actin roles in nuclear architecture. Understanding the mechanisms involving ABPs will definitely lead us to the principles of the regulation of gene expression performed via concerting nuclear and cytoplasmic processes.
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Affiliation(s)
- E Castano
- Department of Biology of the Cell Nucleus, Institute of Molecular Genetics of the ASCR, Prague, Czech Republic
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47
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Cisterna B, Biggiogera M. Ribosome biogenesis: from structure to dynamics. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2010; 284:67-111. [PMID: 20875629 DOI: 10.1016/s1937-6448(10)84002-x] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
In this chapter we describe the status of the research concerning the nucleolus, the major nuclear body. The nucleolus has been recognized as a dynamic organelle with many more functions than one could imagine. In fact, in addition to its fundamental role in the biogenesis of preribosomes, the nucleolus takes part in many other cellular processes and functions, such as the cell-cycle control and the p53 pathway: the direct or indirect involvement of the nucleolus in these various processes makes it sensitive to their alteration. Moreover, it is worth noting that the different nucleolar factors participating to independent mechanisms show different dynamics of association/disassociation with the nucleolar body.
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Affiliation(s)
- Barbara Cisterna
- Laboratory of Cell Biology and Neurobiology, Department of Animal Biology, University of Pavia, Pavia, Italy
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48
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Woolner S, Bement WM. Unconventional myosins acting unconventionally. Trends Cell Biol 2009; 19:245-52. [PMID: 19406643 DOI: 10.1016/j.tcb.2009.03.003] [Citation(s) in RCA: 114] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2009] [Revised: 03/26/2009] [Accepted: 03/27/2009] [Indexed: 11/26/2022]
Abstract
Unconventional myosins are proteins that bind actin filaments in an ATP-regulated manner. Because of their association with membranes, they have traditionally been viewed as motors that function primarily to transport membranous organelles along actin filaments. Recently, however, a wealth of roles for myosins that are not obviously related to organelle transport have been uncovered, including organization of F-actin, mitotic spindle regulation and gene transcription. Furthermore, it has also become apparent that the motor domains of different myosins vary strikingly in their biophysical attributes. We suggest that the assumption that most unconventional myosins function primarily as organelle transporters might be misguided.
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Affiliation(s)
- Sarah Woolner
- Faculty of Life Sciences, University of Manchester, Oxford Road, Manchester, UK.
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49
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Ajima R, Akazawa H, Kodama M, Takeshita F, Otsuka A, Kohno T, Komuro I, Ochiya T, Yokota J. Deficiency of Myo18B in mice results in embryonic lethality with cardiac myofibrillar aberrations. Genes Cells 2008; 13:987-99. [PMID: 18761673 DOI: 10.1111/j.1365-2443.2008.01226.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Myo18B is an unconventional myosin family protein expressed predominantly in muscle cells. Although conventional myosins are known to be localized on the A-bands and function as a molecular motor for muscle contraction, Myo18B protein was localized on the Z-lines of myofibrils in striated muscles. Like Myo18A, another 18th class of myosin, the N-terminal unique domain of the protein and not the motor domain and the coiled-coil tail is critical for its localization to F-actin in myocytes. Myo18B expression was induced by myogenic differentiation through the binding of myocyte-specific enhancer factor-2 to its promoter. Deficiency of Myo18B caused an embryonic lethality in mice accompanied by disruption of myofibrillar structures in cardiac myocytes at embryonic day 10.5. Thus, Myo18B is a unique unconventional myosin that is predominantly expressed in myocytes and whose expression is essential for the development and/or maintenance of myofibrillar structure.
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Affiliation(s)
- Rieko Ajima
- Biology Division, National Cancer Center Research Institute, Tokyo 104-0045, Japan
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50
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Pranchevicius MCS, Baqui MMA, Ishikawa-Ankerhold HC, Lourenço EV, Leão RM, Banzi SR, dos Santos CT, Roque-Barreira MC, Barreira MCR, Espreafico EM, Larson RE. Myosin Va phosphorylated on Ser1650 is found in nuclear speckles and redistributes to nucleoli upon inhibition of transcription. ACTA ACUST UNITED AC 2008; 65:441-56. [PMID: 18330901 DOI: 10.1002/cm.20269] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Nuclear actin and nuclear myosins have been implicated in the regulation of gene expression in vertebrate cells. Myosin V is a class of actin-based motor proteins involved in cytoplasmic vesicle transport and anchorage, spindle-pole alignment and mRNA translocation. In this study, myosin-Va, phosphorylated on a conserved serine in the tail domain (phospho-ser(1650) MVa), was localized to subnuclear compartments. A monoclonal antibody, 9E6, raised against a peptide corresponding to phosphoserine(1650) and flanking regions of the murine myosin Va sequence, was immunoreactive to myosin Va heavy chain in cellular and nuclear extracts of HeLa cells, PC12 cells and B16-F10 melanocytes. Immunofluorescence microscopy with this antibody revealed discrete irregular spots within the nucleoplasm that colocalized with SC35, a splicing factor that earmarks nuclear speckles. Phospho-ser(1650) MVa was not detected in other nuclear compartments, such as condensed chromatin, Cajal bodies, gems and perinucleolar caps. Although nucleoli also were not labeled by 9E6 under normal conditions, inhibition of transcription in HeLa cells by actinomycin D caused the redistribution of phospho-ser(1650) MVa to nucleoli, as well as separating a fraction of phospho-ser(1650) MVa from SC35 into near-neighboring particles. These observations indicate a novel role for myosin Va in nuclear compartmentalization and offer a new lead towards the understanding of actomyosin-based gene regulation.
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Affiliation(s)
- Maria Cristina S Pranchevicius
- Department of Cellular and Molecular Biology, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, São Paulo, Brazil
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