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Gene ACTG1; Gene ACTG_HUMAN
Gamma-actin, gamma(cyto)-actin, is a 42 kDa, 374 amino acids long protein coded by the ACTG gene (Gene map locus 17q25) that is post-translationally modified (PTM) by N-terminal acetylation, methylation (tele-His73) and tyrosine phosphorylation (Tyr169). Gamma-Actin is the monomeric (G-Actin) component of the two-stranded helix structural filament, filamentous actin (F-actin) found in the cytoplasm.
Gamma-actin is one of six actin proteins coded by the highly conserved actin gene family. This family also includes: alpha skeletal, skActin (ACTA1); alpha cardiac, caActin, (ACTC1); alpha vascular, SMactin, (ACTA2); beta-actin (ACTB); and gamma enteric, SMGA (ACTG2) actin genes. Actin isotypes are sequence diverse primarily in their N-terminal regions.
Gamma-actin is the predominant actin isoform versus beta actin in auditory hair cells where it is found in cores of sensory hairs (stereocilia), the cuticular plate, and the zonula adherens ring. Mammalian auditory hair cells are terminally differentiated cells equipped with mechanosensitive, microvilli-like organelles called stereocilia. Mutations in gamma-actin have been linked to non-syndromic sensorineural deafness dominant type 20 (DFNA20; DFNA26).
Gamma(cyto)-actin, while not the dominant actin in skeletal muscle, plays an important role in the stabilization of the link between the sarcolemma and the sarcomere. It binds directly to dystrophin, the gene defective in Duchenne muscular dystrophy and alpha actinin. Gamma(cyto)-actin is localized within costameres which are rib-like lattice structures that circumferentially align with the Z-bands of the myofibril sarcomeres. Gamma(cyto)-actin also binds with numerous other costameric proteins including plectin, spectrin, gamma filamin, talin, vinculin, tropomodulin-1 and syndecan-4. Absence of gamma actin in skeletal muscle leads to myopathies that manifest as overt muscle weakness with progressive muscle fiber necrosis/regeneration.
Sigma offers antibodies and shRNAs useful for the study of ACTG1 gene products.
References:
Ervasti JM. (2003) Costameres: the Achilles' heel of Herculean muscle. J Biol Chem. 278: 13591-4. Epub 2003 Jan 29. Comment in: J Biol Chem. 278: 12599-600.
Höfer D, Ness W, Drenckhahn D. Sorting of actin isoforms in chicken auditory hair cells. J Cell Sci. 110: 765-70.
Rybakova IN, Patel JR, Ervasti JM. (2000) The dystrophin complex forms a mechanically strong link between the sarcolemma and costameric actin. J Cell Biol. 150: 1209-14.
Sonnemann KJ, Fitzsimons DP, Patel JR, Liu Y, Schneider MF, Moss RL, Ervasti JM. (2006) Cytoplasmic gamma-actin is not required for skeletal muscle development but its absence leads to a progressive myopathy. Dev Cell. 11: 387-97.
Zhu M, Yang T, Wei S, DeWan AT, Morell RJ, Elfenbein JL, Fisher RA, Leal SM, Smith RJ, Friderici KH. (2003) Mutations in the gamma-actin gene (ACTG1) are associated with dominant progressive deafness (DFNA20/26). Dev Cell. 11: 387-97.
Footnote: Gene Data Sources: HGNC, Entrez Gene, UniProt/Swiss-Prot, UniProt/TrEMBL, GDB, OMIM, GeneLoc, Ensembl.
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