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Greve JN, Marquardt A, Heiringhoff R, Reindl T, Thiel C, Di Donato N, Taft MH, Manstein DJ. The non-muscle actinopathy-associated mutation E334Q in cytoskeletal γ-actin perturbs interaction of actin filaments with myosin and ADF/cofilin family proteins. eLife 2024; 12:RP93013. [PMID: 38446501 PMCID: PMC10942649 DOI: 10.7554/elife.93013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/07/2024] Open
Abstract
Various heterozygous cytoskeletal γ-actin mutations have been shown to cause Baraitser-Winter cerebrofrontofacial syndrome, non-syndromic hearing loss, or isolated eye coloboma. Here, we report the biochemical characterization of human cytoskeletal γ-actin carrying mutation E334Q, a mutation that leads to a hitherto unspecified non-muscle actinopathy. Following expression, purification, and removal of linker and thymosin β4 tag sequences, the p.E334Q monomers show normal integration into linear and branched actin filaments. The mutation does not affect thermal stability, actin filament nucleation, elongation, and turnover. Model building and normal mode analysis predict significant differences in the interaction of p.E334Q filaments with myosin motors and members of the ADF/cofilin family of actin-binding proteins. Assays probing the interactions of p.E334Q filaments with human class 2 and class 5 myosin motor constructs show significant reductions in sliding velocity and actin affinity. E334Q differentially affects cofilin-mediated actin dynamics by increasing the rate of cofilin-mediated de novo nucleation of actin filaments and decreasing the efficiency of cofilin-mediated filament severing. Thus, it is likely that p.E334Q-mediated changes in myosin motor activity, as well as filament turnover, contribute to the observed disease phenotype.
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Affiliation(s)
- Johannes N Greve
- Institute for Biophysical Chemistry, Hannover Medical School, Fritz Hartmann Centre for MedicalHannoverGermany
| | - Anja Marquardt
- Institute for Biophysical Chemistry, Hannover Medical School, Fritz Hartmann Centre for MedicalHannoverGermany
| | - Robin Heiringhoff
- Institute for Biophysical Chemistry, Hannover Medical School, Fritz Hartmann Centre for MedicalHannoverGermany
| | - Theresia Reindl
- Institute for Biophysical Chemistry, Hannover Medical School, Fritz Hartmann Centre for MedicalHannoverGermany
| | - Claudia Thiel
- Institute for Biophysical Chemistry, Hannover Medical School, Fritz Hartmann Centre for MedicalHannoverGermany
| | | | - Manuel H Taft
- Institute for Biophysical Chemistry, Hannover Medical School, Fritz Hartmann Centre for MedicalHannoverGermany
| | - Dietmar J Manstein
- Institute for Biophysical Chemistry, Hannover Medical School, Fritz Hartmann Centre for MedicalHannoverGermany
- Division for Structural Biochemistry, Hannover Medical SchoolHannoverGermany
- RESiST, Cluster of Excellence 2155, Hannover Medical SchoolHannoverGermany
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Steffensen KE, Dawson JF. Actin's C-terminus coordinates actin structural changes and functions. Cytoskeleton (Hoboken) 2023; 80:313-329. [PMID: 37036084 DOI: 10.1002/cm.21757] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Revised: 03/17/2023] [Accepted: 03/30/2023] [Indexed: 04/11/2023]
Abstract
Actin is essential to eukaryotic cellular processes. Actin's C-terminus appears to play a direct role in modulating actin's structure and properties, facilitating the binding and function of actin-binding proteins (ABPs). The structural and functional characterization of filamentous actin's C-terminus has been impeded by its inherent flexibility, as well as actin's resistance to crystallization for x-ray diffraction and the historical resolution constraints associated with electron microscopy. Many biochemical studies have established that actin's C-terminus must retain its flexibility and structural integrity to modulate actin's structure and functions. For example, C-terminal structural changes are known to affect nucleotide binding and exchange, as well as propagate actin structural changes throughout extensive allosteric networks, facilitating the binding and function of ABPs. Advances in electron microscopy have resulted in high-resolution structures of filamentous actin, providing insights into subtle structural changes that are mediated by actin's C-terminus. Here, we review existing knowledge establishing the importance of actin's C-terminus within actin structural changes and functions and discuss how modern structural characterization techniques provide the tools to understand the role of actin's C-terminus in cellular processes.
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Affiliation(s)
- Karl E Steffensen
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
| | - John F Dawson
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
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DFNA20/26 and Other ACTG1-Associated Phenotypes: A Case Report and Review of the Literature. Audiol Res 2021; 11:582-593. [PMID: 34698053 PMCID: PMC8544197 DOI: 10.3390/audiolres11040052] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Revised: 10/10/2021] [Accepted: 10/13/2021] [Indexed: 02/08/2023] Open
Abstract
Since the early 2000s, an ever-increasing subset of missense pathogenic variants in the ACTG1 gene has been associated with an autosomal-dominant, progressive, typically post-lingual non-syndromic hearing loss (NSHL) condition designed as DFNA20/26. ACTG1 gene encodes gamma actin, the predominant actin protein in the cytoskeleton of auditory hair cells; its normal expression and function are essential for the stereocilia maintenance. Different gain-of-function pathogenic variants of ACTG1 have been associated with two major phenotypes: DFNA20/26 and Baraitser-Winter syndrome, a multiple congenital anomaly disorder. Here, we report a novel ACTG1 variant [c.625G>A (p. Val209Met)] in an adult patient with moderate-severe NSHL characterized by a downsloping audiogram. The patient, who had a clinical history of slowly progressive NSHL and tinnitus, was referred to our laboratory for the analysis of a large panel of NSHL-associated genes by next generation sequencing. An extensive review of previously reported ACTG1 variants and their associated phenotypes was also performed.
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Teng GZ, Dawson JF. The Dark Side of Actin: Cardiac actin variants highlight the role of allostery in disease development. Arch Biochem Biophys 2020; 695:108624. [PMID: 33049292 DOI: 10.1016/j.abb.2020.108624] [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: 06/30/2020] [Revised: 09/24/2020] [Accepted: 10/05/2020] [Indexed: 10/23/2022]
Abstract
Mutations in the α-cardiac actin ACTC1 gene cause dilated or hypertrophic cardiomyopathy. These diseases are the result of changes in protein interactions between ACTC protein and force-generating β-myosin or the calcium-dependent cardiac-tropomyosin (cTm) and cardiac troponin (cTn) regulatory complex, altering the overall contractile force. The T126I and S271F ACTC variants possess amino acid substitutions on the other side of actin relative to the myosin or regulatory protein binding sites on what we call the "dark side" of actin. The T126I change results in hyposensitivity to calcium, in accordance with the calcium sensitivity pathway of cardiomyopathy development while the S271F change alters the maximum in vitro motility sliding speed, reflecting a change in maximum force. These results demonstrate the role of actin allostery in the cardiac disease development.
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Affiliation(s)
- Grace Zi Teng
- Department of Molecular & Cellular Biology and Centre for Cardiovascular Investigations, University of Guelph, Guelph, ON, N1G 2W1, Canada
| | - John F Dawson
- Department of Molecular & Cellular Biology and Centre for Cardiovascular Investigations, University of Guelph, Guelph, ON, N1G 2W1, Canada.
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Jepsen L, Sept D. Effects of Nucleotide and End-Dependent Actin Conformations on Polymerization. Biophys J 2020; 119:1800-1810. [PMID: 33080221 DOI: 10.1016/j.bpj.2020.09.024] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Revised: 09/04/2020] [Accepted: 09/10/2020] [Indexed: 12/23/2022] Open
Abstract
The regulation of actin is key for controlled cellular function. Filaments are regulated by actin-binding proteins, but the nucleotide state of actin is also an important factor. From extended molecular dynamics simulations, we find that both nucleotide states of the actin monomer have significantly less twist than their crystal structures and that the ATP monomer is flatter than the ADP form. We also find that the filament's pointed end is flatter than the remainder of the filament and has a conformation distinct from G-actin, meaning that incoming monomers would need to undergo isomerization that would weaken the affinity and slow polymerization. Conversely, the barbed end of the filament takes on a conformation nearly identical to the ATP monomer, enhancing ATP G-actin's ability to polymerize as compared with ADP G-actin. The thermodynamic penalty imposed by differences in isomerization for the ATP and ADP growth at the barbed end exactly matches experimental results.
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Affiliation(s)
- Lauren Jepsen
- Department of Biomedical Engineering and Center for Computational Medicine and Bioinformatics, University of Michigan, Ann Arbor, Michigan
| | - David Sept
- Department of Biomedical Engineering and Center for Computational Medicine and Bioinformatics, University of Michigan, Ann Arbor, Michigan.
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Yetman AT, Starr LJ. Newly described recessive MYH11 disorder with clinical overlap of Multisystemic smooth muscle dysfunction and Megacystis microcolon hypoperistalsis syndromes. Am J Med Genet A 2019; 176:1011-1014. [PMID: 29575632 DOI: 10.1002/ajmg.a.38647] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2017] [Revised: 01/29/2018] [Accepted: 01/29/2018] [Indexed: 12/12/2022]
Abstract
We describe a neonatal patient with fixed dilated pupils and pulmonary, bladder, and bowel dysfunction suspicious for the presence of ACTA2 R179 mediated multisystemic smooth muscle dysfunction syndrome. Whole exome sequencing revealed compound heterozygous mutations in MYH11 after ACTA2 specific testing revealed no abnormalities. The child lived until 18 months of age and represents the only reported case of an MYH11 compound heterozygote with widespread smooth muscle dysfunction.
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Affiliation(s)
- Anji T Yetman
- Division of Cardiology, Department of Pediatrics, University of Nebraska Medical Center, Omaha, Nebraska
| | - Lois J Starr
- Division of Medical Genetics, Department of Pediatrics, University of Nebraska Medical Center, Omaha, Nebraska
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Varland S, Vandekerckhove J, Drazic A. Actin Post-translational Modifications: The Cinderella of Cytoskeletal Control. Trends Biochem Sci 2019; 44:502-516. [PMID: 30611609 DOI: 10.1016/j.tibs.2018.11.010] [Citation(s) in RCA: 80] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2018] [Revised: 11/22/2018] [Accepted: 11/27/2018] [Indexed: 11/30/2022]
Abstract
Actin is one of the most abundant proteins in eukaryotic cells and the main component of the microfilament system. It plays essential roles in numerous cellular activities, including muscle contraction, maintenance of cell integrity, and motility, as well as transcriptional regulation. Besides interacting with various actin-binding proteins (ABPs), proper actin function is regulated by post-translational modifications (PTMs), such as acetylation, arginylation, oxidation, and others. Here, we explain how actin PTMs can contribute to filament formation and stability, and may have additional actin regulatory functions, which potentially contribute to disease development.
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Affiliation(s)
- Sylvia Varland
- Department of Biomedicine, University of Bergen, Jonas Lies vei 91, N-5020 Bergen, Norway; Department of Biological Sciences, University of Bergen, Thormøhlensgate 53 A, N-5020 Bergen, Norway; Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, 160 College Street, Toronto, ON M5S 3E1, Canada
| | - Joël Vandekerckhove
- Department of Biochemistry, UGent Center for Medical Biotechnology, Ghent University, Albert Baertsoenkaai 3, 9000 Gent, Belgium
| | - Adrian Drazic
- Department of Biomedicine, University of Bergen, Jonas Lies vei 91, N-5020 Bergen, Norway.
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Abstract
The highly similar cytoplasmic β- and γ-actins differ by only four functionally similar amino acids, yet previous in vitro and in vivo data suggest that they support unique functions due to striking phenotypic differences between Actb and Actg1 null mouse and cell models. To determine whether the four amino acid variances were responsible for the functional differences between cytoplasmic actins, we gene edited the endogenous mouse Actb locus to translate γ-actin protein. The resulting mice and primary embryonic fibroblasts completely lacked β-actin protein, but were viable and did not present with the most overt and severe cell and organismal phenotypes observed with gene knockout. Nonetheless, the edited mice exhibited progressive high-frequency hearing loss and degeneration of actin-based stereocilia as previously reported for hair cell-specific Actb knockout mice. Thus, β-actin protein is not required for general cellular functions, but is necessary to maintain auditory stereocilia.
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