Actin, cytoplasmic 2 explained

Actin, cytoplasmic 2, or gamma-actin is a protein that in humans is encoded by the ACTG1 gene.^[1] Gamma-actin is widely expressed in cellular cytoskeletons of many tissues; in adult striated muscle cells, gamma-actin is localized to Z-discs and costamere structures, which are responsible for force transduction and transmission in muscle cells. Mutations in ACTG1 have been associated with nonsyndromic hearing loss and Baraitser-Winter syndrome, as well as susceptibility of adolescent patients to vincristine toxicity.

Structure

Human gamma-actin is 41.8 kDa in molecular weight and 375 amino acids in length.^[2] Actins are highly conserved proteins that are involved in various types of cell motility, and maintenance of the cytoskeleton. In vertebrates, three main groups of actin paralogs, alpha, beta, and gamma, have been identified.^[3]

The alpha actins are found in muscle tissues and are a major constituent of the sarcomere contractile apparatus. The beta and gamma actins co-exist in most cell types as components of the cytoskeleton, and as mediators of internal cell motility. Actin, gamma 1, encoded by this gene, is found in non-muscle cells in the cytoplasm, and in muscle cells at costamere structures, or transverse points of cell-cell adhesion that run perpendicular to the long axis of myocytes.^{[4] [5] [6]}

Function

In myocytes, sarcomeres adhere to the sarcolemma via costameres, which align at Z-discs and M-lines.^[7] The two primary cytoskeletal components of costameres are desmin intermediate filaments and gamma-actin microfilaments.^[8] It has been shown that gamma-actin interacting with another costameric protein dystrophin is critical for costameres forming mechanically strong links between the cytoskeleton and the sarcolemmal membrane.^{[9] [10]} Additional studies have shown that gamma-actin colocalizes with alpha-actinin and GFP-labeled gamma actin localized to Z-discs, whereas GFP-alpha-actin localized to pointed ends of thin filaments, indicating that gamma actin specifically localizes to Z-discs in striated muscle cells.^{[11] [12] [13]}

During development of myocytes, gamma actin is thought to play a role in the organization and assembly of developing sarcomeres, evidenced in part by its early colocalization with alpha-actinin.^[14] Gamma-actin is eventually replaced by sarcomeric alpha-actin isoforms,^{[15] [16] [17]} with low levels of gamma-actin persisting in adult myocytes which associate with Z-disc and costamere domains.^{[11] [18] [19]}

Insights into the function of gamma-actin in muscle have come from studies employing transgenesis. In a skeletal muscle-specific knockout of gamma-actin in mice, these animals showed no detectable abnormalities in development; however, knockout mice showed muscle weakness and fiber necrosis, along with decreased isometric twitch force, disrupted intrafibrillar and interfibrillar connections among myocytes, and myopathy.^[20]

Clinical significance

An autosomal dominant mutation in ACTG1 in the DFNA20/26 locus at 17q25-qter was identified in patients with hearing loss. A Thr278Ile mutation was identified in helix 9 of gamma-actin protein, which is predicted to alter protein structure. This study identified the first disease causing mutation in gamma-actin and underlies the importance of gamma-actin as structural elements of the inner ear hair cells.^[21] Since then, other ACTG1 mutations have been linked to nonsyndromic hearing loss, including Met305Thr.^[22]

A missense mutation in ACTG1 at Ser155Phe has also been identified in patients with Baraitser-Winter syndrome, which is a developmental disorder characterized by congenital ptosis, excessively-arched eyebrows, hypertelorism, ocular colobomata, lissencephaly, short stature, seizures and hearing loss.^{[23] [24]}

Differential expression of ACTG1 mRNA was also identified in patients with Sporadic Amyotrophic Lateral Sclerosis, a devastating disease with unknown causality, using a sophisticated bioinformatics approach employing Affymetrix long-oligonucleotide BaFL methods.^[25]

Single nucleotide polymorphisms in ACTG1 have been associated with vincristine toxicity, which is part of the standard treatment regimen for childhood acute lymphoblastic leukemia. Neurotoxicity was more frequent in patients that were ACTG1 Gly310Ala mutation carriers, suggesting that this may play a role in patient outcomes from vincristine treatment.^[26]

Interactions

ACTG1 has been shown to interact with:

• CAP1,^[27]
• DMD,^[9]
• TMSB4X,^{[28] [29]} and
• Plectin.^[30]

See also

• Actin

Further reading

• Snásel J, Pichová I . The cleavage of host cell proteins by HIV-1 protease . Folia Biologica . 42 . 5 . 227–30 . 1997 . 8997639 . 10.1007/BF02818986 . 7617882 .
• Rodríguez Del Castillo A, Vitale ML, Trifaró JM . Ca2+ and pH determine the interaction of chromaffin cell scinderin with phosphatidylserine and phosphatidylinositol 4,5,-biphosphate and its cellular distribution during nicotinic-receptor stimulation and protein kinase C activation . The Journal of Cell Biology . 119 . 4 . 797–810 . Nov 1992 . 1331119 . 2289683 . 10.1083/jcb.119.4.797 .
• Adams LD, Tomasselli AG, Robbins P, Moss B, Heinrikson RL . HIV-1 protease cleaves actin during acute infection of human T-lymphocytes . AIDS Research and Human Retroviruses . 8 . 2 . 291–5 . Feb 1992 . 1540415 . 10.1089/aid.1992.8.291 .
• Dawson SJ, White LA . Treatment of Haemophilus aphrophilus endocarditis with ciprofloxacin . The Journal of Infection . 24 . 3 . 317–20 . May 1992 . 1602151 . 10.1016/S0163-4453(05)80037-4 .
• Tomasselli AG, Hui JO, Adams L, Chosay J, Lowery D, Greenberg B, Yem A, Deibel MR, Zürcher-Neely H, Heinrikson RL . Actin, troponin C, Alzheimer amyloid precursor protein and pro-interleukin 1 beta as substrates of the protease from human immunodeficiency virus . The Journal of Biological Chemistry . 266 . 22 . 14548–53 . Aug 1991 . 10.1016/S0021-9258(18)98721-1 . 1907279 . free .
• Shoeman RL, Kesselmier C, Mothes E, Höner B, Traub P . Non-viral cellular substrates for human immunodeficiency virus type 1 protease . FEBS Letters . 278 . 2 . 199–203 . Jan 1991 . 1991513 . 10.1016/0014-5793(91)80116-K . 37002682 . free .
• Erba HP, Eddy R, Shows T, Kedes L, Gunning P . Structure, chromosome location, and expression of the human gamma-actin gene: differential evolution, location, and expression of the cytoskeletal beta- and gamma-actin genes . Molecular and Cellular Biology . 8 . 4 . 1775–89 . Apr 1988 . 2837653 . 363338 . 10.1128/mcb.8.4.1775.
• Vandekerckhove J, Schering B, Bärmann M, Aktories K . Botulinum C2 toxin ADP-ribosylates cytoplasmic beta/gamma-actin in arginine 177 . The Journal of Biological Chemistry . 263 . 2 . 696–700 . Jan 1988 . 10.1016/S0021-9258(19)35408-0 . 3335520 . free .
• Chou CC, Davis RC, Fuller ML, Slovin JP, Wong A, Wright J, Kania S, Shaked R, Gatti RA, Salser WA . Gamma-actin: unusual mRNA 3'-untranslated sequence conservation and amino acid substitutions that may be cancer related . Proceedings of the National Academy of Sciences of the United States of America . 84 . 9 . 2575–9 . May 1987 . 3472224 . 304700 . 10.1073/pnas.84.9.2575 . 1987PNAS...84.2575C . free .
• Hesterberg LK, Weber K . Isolation of a domain of villin retaining calcium-dependent interaction with G-actin, but devoid of F-actin fragmenting activity . European Journal of Biochemistry . 154 . 1 . 135–40 . Jan 1986 . 3510866 . 10.1111/j.1432-1033.1986.tb09368.x . free .
• Erba HP, Gunning P, Kedes L . Nucleotide sequence of the human gamma cytoskeletal actin mRNA: anomalous evolution of vertebrate non-muscle actin genes . Nucleic Acids Research . 14 . 13 . 5275–94 . Jul 1986 . 3737401 . 311540 . 10.1093/nar/14.13.5275 .
• Fuchs E, Kim KH, Hanukoglu I, Tanese N . The evolution and complexity of the genes encoding the cytoskeletal proteins of human epidermal cells . Current Problems in Dermatology . 11 . 27–44 . 1984 . 6686106 . 10.1159/000408662. 978-3-8055-3752-0 .
• Gunning P, Ponte P, Okayama H, Engel J, Blau H, Kedes L . Isolation and characterization of full-length cDNA clones for human alpha-, beta-, and gamma-actin mRNAs: skeletal but not cytoplasmic actins have an amino-terminal cysteine that is subsequently removed . Molecular and Cellular Biology . 3 . 5 . 787–95 . May 1983 . 6865942 . 368601 . 10.1128/mcb.3.5.787.
• Bretscher A, Weber K . Villin is a major protein of the microvillus cytoskeleton which binds both G and F actin in a calcium-dependent manner . Cell . 20 . 3 . 839–47 . Jul 1980 . 6893424 . 10.1016/0092-8674(80)90330-X . 568395 .
• Pedrotti B, Colombo R, Islam K . Microtubule associated protein MAP1A is an actin-binding and crosslinking protein . Cell Motility and the Cytoskeleton . 29 . 2 . 110–6 . 1995 . 7820861 . 10.1002/cm.970290203 .
• Pope B, Maciver S, Weeds A . Localization of the calcium-sensitive actin monomer binding site in gelsolin to segment 4 and identification of calcium binding sites . Biochemistry . 34 . 5 . 1583–8 . Feb 1995 . 7849017 . 10.1021/bi00005a014 .
• Jesaitis AJ, Erickson RW, Klotz KN, Bommakanti RK, Siemsen DW . Functional molecular complexes of human N-formyl chemoattractant receptors and actin . Journal of Immunology . 151 . 10 . 5653–65 . Nov 1993 . 10.4049/jimmunol.151.10.5653 . 8228254 . 45748273 . free .
• Hawkins M, Pope B, Maciver SK, Weeds AG . Human actin depolymerizing factor mediates a pH-sensitive destruction of actin filaments . Biochemistry . 32 . 38 . 9985–93 . Sep 1993 . 8399167 . 10.1021/bi00089a014 .
• Yu FX, Lin SC, Morrison-Bogorad M, Atkinson MA, Yin HL . Thymosin beta 10 and thymosin beta 4 are both actin monomer sequestering proteins . The Journal of Biological Chemistry . 268 . 1 . 502–9 . Jan 1993 . 10.1016/S0021-9258(18)54179-X . 8416954 . free .
• Jalaguier S, Mornet D, Mesnier D, Léger JJ, Auzou G . Human mineralocorticoid receptor interacts with actin under mineralocorticoid ligand modulation . FEBS Letters . 384 . 2 . 112–6 . Apr 1996 . 8612804 . 10.1016/0014-5793(96)00295-5 . 34685894 . free .

Notes and References

1. Web site: Entrez Gene: ACTG1 actin, gamma 1.
2. Web site: Protein sequence for human ACTG1 (Uniprot ID: P63261). Cardiac Organellar Protein Atlas Knowledgebase (COPaKB). 18 July 2015. https://web.archive.org/web/20150721173652/http://www.heartproteome.org/copa/ProteinInfo.aspx?QType=Protein%20ID&QValue=P63261. 21 July 2015. dead.
3. Rubenstein PA . The functional importance of multiple actin isoforms . BioEssays . 12 . 7 . 309–15 . Jul 1990 . 2203335 . 10.1002/bies.950120702 . 2163289 .
4. Craig SW, Pardo JV . Gamma actin, spectrin, and intermediate filament proteins colocalize with vinculin at costameres, myofibril-to-sarcolemma attachment sites . Cell Motility . 3 . 5–6 . 449–62 . 1983 . 6420066 . 10.1002/cm.970030513.
5. Pardo JV, Siliciano JD, Craig SW . A vinculin-containing cortical lattice in skeletal muscle: transverse lattice elements ("costameres") mark sites of attachment between myofibrils and sarcolemma . Proceedings of the National Academy of Sciences of the United States of America . 80 . 4 . 1008–12 . Feb 1983 . 6405378 . 10.1073/pnas.80.4.1008 . 393517. 1983PNAS...80.1008P . free .
6. Danowski BA, Imanaka-Yoshida K, Sanger JM, Sanger JW . Costameres are sites of force transmission to the substratum in adult rat cardiomyocytes . The Journal of Cell Biology . 118 . 6 . 1411–20 . Sep 1992 . 1522115 . 10.1083/jcb.118.6.1411 . 2289604.
7. Clark KA, McElhinny AS, Beckerle MC, Gregorio CC . Striated muscle cytoarchitecture: an intricate web of form and function . Annual Review of Cell and Developmental Biology . 18 . 637–706 . 2002 . 12142273 . 10.1146/annurev.cellbio.18.012502.105840 .
8. Kee AJ, Gunning PW, Hardeman EC . Diverse roles of the actin cytoskeleton in striated muscle . Journal of Muscle Research and Cell Motility . 30 . 5–6 . 187–97 . 2009 . 19997772 . 10.1007/s10974-009-9193-x . 6632615 .
9. Rybakova IN, Patel JR, Ervasti JM . The dystrophin complex forms a mechanically strong link between the sarcolemma and costameric actin . The Journal of Cell Biology . 150 . 5 . 1209–14 . Sep 2000 . 10974007 . 10.1083/jcb.150.5.1209 . 2175263.
10. Ervasti JM . Costameres: the Achilles' heel of Herculean muscle . The Journal of Biological Chemistry . 278 . 16 . 13591–4 . Apr 2003 . 12556452 . 10.1074/jbc.R200021200 . free .
11. Nakata T, Nishina Y, Yorifuji H . Cytoplasmic gamma actin as a Z-disc protein . Biochemical and Biophysical Research Communications . 286 . 1 . 156–63 . Aug 2001 . 11485322 . 10.1006/bbrc.2001.5353 .
12. Papponen H, Kaisto T, Leinonen S, Kaakinen M, Metsikkö K . Evidence for gamma-actin as a Z disc component in skeletal myofibers . Experimental Cell Research . 315 . 2 . 218–25 . Jan 2009 . 19013151 . 10.1016/j.yexcr.2008.10.021 .
13. Vlahovich N, Kee AJ, Van der Poel C, Kettle E, Hernandez-Deviez D, Lucas C, Lynch GS, Parton RG, Gunning PW, Hardeman EC . Cytoskeletal tropomyosin Tm5NM1 is required for normal excitation-contraction coupling in skeletal muscle . Molecular Biology of the Cell . 20 . 1 . 400–9 . Jan 2009 . 19005216 . 10.1091/mbc.E08-06-0616 . 2613127.
14. Lloyd CM, Berendse M, Lloyd DG, Schevzov G, Grounds MD . A novel role for non-muscle gamma-actin in skeletal muscle sarcomere assembly . Experimental Cell Research . 297 . 1 . 82–96 . Jul 2004 . 15194427 . 10.1016/j.yexcr.2004.02.012 .
15. Schwartz RJ, Rothblum KN . Gene switching in myogenesis: differential expression of the chicken actin multigene family . Biochemistry . 20 . 14 . 4122–9 . Jul 1981 . 7284314 . 10.1021/bi00517a027.
16. Shani M, Zevin-Sonkin D, Saxel O, Carmon Y, Katcoff D, Nudel U, Yaffe D . The correlation between the synthesis of skeletal muscle actin, myosin heavy chain, and myosin light chain and the accumulation of corresponding mRNA sequences during myogenesis . Developmental Biology . 86 . 2 . 483–92 . Sep 1981 . 7286410 . 10.1016/0012-1606(81)90206-2.
17. von Arx P, Bantle S, Soldati T, Perriard JC . Dominant negative effect of cytoplasmic actin isoproteins on cardiomyocyte cytoarchitecture and function . The Journal of Cell Biology . 131 . 6 Pt 2 . 1759–73 . Dec 1995 . 8557743 . 10.1083/jcb.131.6.1759 . 2120671.
18. Hanft LM, Bogan DJ, Mayer U, Kaufman SJ, Kornegay JN, Ervasti JM . Cytoplasmic gamma-actin expression in diverse animal models of muscular dystrophy . Neuromuscular Disorders . 17 . 7 . 569–74 . Jul 2007 . 17475492 . 10.1016/j.nmd.2007.03.004 . 1993539.
19. Kee AJ, Schevzov G, Nair-Shalliker V, Robinson CS, Vrhovski B, Ghoddusi M, Qiu MR, Lin JJ, Weinberger R, Gunning PW, Hardeman EC . Sorting of a nonmuscle tropomyosin to a novel cytoskeletal compartment in skeletal muscle results in muscular dystrophy . The Journal of Cell Biology . 166 . 5 . 685–96 . Aug 2004 . 15337777 . 10.1083/jcb.200406181 . 2172434.
20. Sonnemann KJ, Fitzsimons DP, Patel JR, Liu Y, Schneider MF, Moss RL, Ervasti JM . Cytoplasmic gamma-actin is not required for skeletal muscle development but its absence leads to a progressive myopathy . Developmental Cell . 11 . 3 . 387–97 . Sep 2006 . 16950128 . 10.1016/j.devcel.2006.07.001 . free .
21. van Wijk E, Krieger E, Kemperman MH, De Leenheer EM, Huygen PL, Cremers CW, Cremers FP, Kremer H . A mutation in the gamma actin 1 (ACTG1) gene causes autosomal dominant hearing loss (DFNA20/26) . Journal of Medical Genetics . 40 . 12 . 879–84 . Dec 2003 . 14684684 . 10.1136/jmg.40.12.879 . 1735337.
22. Park G, Gim J, Kim AR, Han KH, Kim HS, Oh SH, Park T, Park WY, Choi BY . Multiphasic analysis of whole exome sequencing data identifies a novel mutation of ACTG1 in a nonsyndromic hearing loss family . BMC Genomics . 14 . 191 . 18 March 2013 . 23506231 . 10.1186/1471-2164-14-191 . 3608096 . free .
23. Rivière JB, van Bon BW, Hoischen A, Kholmanskikh SS, O'Roak BJ, Gilissen C, Gijsen S, Sullivan CT, Christian SL, Abdul-Rahman OA, Atkin JF, Chassaing N, Drouin-Garraud V, Fry AE, Fryns JP, Gripp KW, Kempers M, Kleefstra T, Mancini GM, Nowaczyk MJ, van Ravenswaaij-Arts CM, Roscioli T, Marble M, Rosenfeld JA, Siu VM, de Vries BB, Shendure J, Verloes A, Veltman JA, Brunner HG, Ross ME, Pilz DT, Dobyns WB . De novo mutations in the actin genes ACTB and ACTG1 cause Baraitser-Winter syndrome . Nature Genetics . 44 . 4 . 440–4, S1–2 . Apr 2012 . 22366783 . 10.1038/ng.1091 . 3677859.
24. Di Donato N, Rump A, Koenig R, Der Kaloustian VM, Halal F, Sonntag K, Krause C, Hackmann K, Hahn G, Schrock E, Verloes A . Severe forms of Baraitser-Winter syndrome are caused by ACTB mutations rather than ACTG1 mutations . European Journal of Human Genetics . 22 . 2 . 179–83 . Feb 2014 . 23756437 . 10.1038/ejhg.2013.130 . 3895648.
25. Baciu C, Thompson KJ, Mougeot JL, Brooks BR, Weller JW . The LO-BaFL method and ALS microarray expression analysis . BMC Bioinformatics . 13 . 244 . 24 September 2012 . 23006766 . 10.1186/1471-2105-13-244 . 3526454 . free .
26. Ceppi F, Langlois-Pelletier C, Gagné V, Rousseau J, Ciolino C, De Lorenzo S, Kevin KM, Cijov D, Sallan SE, Silverman LB, Neuberg D, Kutok JL, Sinnett D, Laverdière C, Krajinovic M . Polymorphisms of the vincristine pathway and response to treatment in children with childhood acute lymphoblastic leukemia . Pharmacogenomics . 15 . 8 . 1105–16 . Jun 2014 . 25084203 . 10.2217/pgs.14.68 . 4443746.
27. Hubberstey A, Yu G, Loewith R, Lakusta C, Young D . Mammalian CAP interacts with CAP, CAP2, and actin . Journal of Cellular Biochemistry . 61 . 3 . 459–66 . Jun 1996 . 8761950 . 10.1002/(SICI)1097-4644(19960601)61:3<459::AID-JCB13>3.0.CO;2-E . 46076387 .
28. Hertzog M, van Heijenoort C, Didry D, Gaudier M, Coutant J, Gigant B, Didelot G, Préat T, Knossow M, Guittet E, Carlier MF . The beta-thymosin/WH2 domain; structural basis for the switch from inhibition to promotion of actin assembly . Cell . 117 . 5 . 611–23 . May 2004 . 15163409 . 10.1016/S0092-8674(04)00403-9 . 8628287 . free .
29. Van Troys M, Dewitte D, Goethals M, Carlier MF, Vandekerckhove J, Ampe C . The actin binding site of thymosin beta 4 mapped by mutational analysis . The EMBO Journal . 15 . 2 . 201–10 . Jan 1996 . 8617195 . 449934 . 10.1002/j.1460-2075.1996.tb00350.x .
30. Hijikata T, Nakamura A, Isokawa K, Imamura M, Yuasa K, Ishikawa R, Kohama K, Takeda S, Yorifuji H . Plectin 1 links intermediate filaments to costameric sarcolemma through beta-synemin, alpha-dystrobrevin and actin . Journal of Cell Science . 121 . Pt 12 . 2062–74 . Jun 2008 . 18505798 . 10.1242/jcs.021634 . 207164281 .