Alpha-actinin-2 is a protein which in humans is encoded by the ACTN2gene.[5] This gene encodes an alpha-actinin isoform that is expressed in both skeletal and cardiac muscles and functions to anchor myofibrillar actin thin filaments and titin to Z-discs.
Structure
Alpha-actinin-2 is a 103.8 kDa protein composed of 894 amino acids.[6][7] Each molecule is rod-shaped (35 nm in length) and it homodimerizes in an anti-parallel fashion. Each monomer has an N-terminal actin-binding region composed of two calponin homology domains, two C-terminalEF hand domains, and four tandem spectrin-like repeats form the rod domain in the central region of the molecule.[8] The high-resolution crystal structure of human alpha-actinin 2 at 3.5 Å was recently resolved.[9] Alpha actinins belong to the spectrin gene superfamily which represents a diverse group of actin-binding cytoskeletal proteins, including spectrin, dystrophin, utrophin and fimbrin.[8] Skeletal, cardiac, and smooth muscle isoforms are localized to the Z-disc and analogous dense bodies, where they help anchor the myofibrillar actin filaments. Alpha-actinin 2 has been shown to interact with KCNA5,[10][11]DLG1,[10]DISC1,[12]MYOZ1,[13]GRIN2B,[14]ADAM12, [15]ACTN3,[16]MYPN,[17]PDLIM3,[18]PKN,[19]MYOT,[20]TTN,[21]NMDAR,[22]SYNPO2,[23]LDB3,[24] and FATZ.[13]
Function
The primary function of alpha-actinin-2 is to crosslink filamentous actin molecules and titin molecules from adjoining sarcomeres at Z-discs, a function that is modulated by phospholipids.[25][26] It is clear from studies by Hampton et al. that this crosslinking can assume a variety of conformations, with preferences for 60° and 120° angles.[27] Alpha-actinin-2 also functions in docking signalling molecules at Z-discs, and additional studies have also implicated alpha-actinin-2 in the binding of cardiac ion channels, Kv1.5 in particular.[10]
^Morris JA, Kandpal G, Ma L, Austin CP (July 2003). "DISC1 (Disrupted-In-Schizophrenia 1) is a centrosome-associated protein that interacts with MAP1A, MIPT3, ATF4/5 and NUDEL: regulation and loss of interaction with mutation". Human Molecular Genetics. 12 (13): 1591–608. doi:10.1093/hmg/ddg162. PMID12812986.
^Chan Y, Tong HQ, Beggs AH, Kunkel LM (July 1998). "Human skeletal muscle-specific alpha-actinin-2 and -3 isoforms form homodimers and heterodimers in vitro and in vivo". Biochemical and Biophysical Research Communications. 248 (1): 134–9. doi:10.1006/bbrc.1998.8920. PMID9675099.
^Linnemann A, van der Ven PF, Vakeel P, Albinus B, Simonis D, Bendas G, Schenk JA, Micheel B, Kley RA, Fürst DO (September 2010). "The sarcomeric Z-disc component myopodin is a multiadapter protein that interacts with filamin and alpha-actinin". European Journal of Cell Biology. 89 (9): 681–92. doi:10.1016/j.ejcb.2010.04.004. PMID20554076.
^Chiu C, Bagnall RD, Ingles J, Yeates L, Kennerson M, Donald JA, Jormakka M, Lind JM, Semsarian C (March 2010). "Mutations in alpha-actinin-2 cause hypertrophic cardiomyopathy: a genome-wide analysis". Journal of the American College of Cardiology. 55 (11): 1127–35. doi:10.1016/j.jacc.2009.11.016. PMID20022194. S2CID116513873.
^Mohapatra B, Jimenez S, Lin JH, Bowles KR, Coveler KJ, Marx JG, Chrisco MA, Murphy RT, Lurie PR, Schwartz RJ, Elliott PM, Vatta M, McKenna W, Towbin JA, Bowles NE (2003). "Mutations in the muscle LIM protein and alpha-actinin-2 genes in dilated cardiomyopathy and endocardial fibroelastosis". Molecular Genetics and Metabolism. 80 (1–2): 207–15. doi:10.1016/s1096-7192(03)00142-2. PMID14567970.
Beggs AH, Phillips HA, Kozman H, Mulley JC, Wilton SD, Kunkel LM, Laing NG (August 1992). "A (CA)n repeat polymorphism for the human skeletal muscle alpha-actinin gene ACTN2 and its localization on the linkage map of chromosome 1". Genomics. 13 (4): 1314–5. doi:10.1016/0888-7543(92)90054-V. PMID1505962.
Yürüker B, Niggli V (February 1992). "Alpha-actinin and vinculin in human neutrophils: reorganization during adhesion and relation to the actin network". Journal of Cell Science. 101 (2): 403–14. doi:10.1242/jcs.101.2.403. PMID1629252.
Tiso N, Majetti M, Stanchi F, Rampazzo A, Zimbello R, Nava A, Danieli GA (November 1999). "Fine mapping and genomic structure of ACTN2, the human gene coding for the sarcomeric isoform of alpha-actinin-2, expressed in skeletal and cardiac muscle". Biochemical and Biophysical Research Communications. 265 (1): 256–9. doi:10.1006/bbrc.1999.1661. PMID10548523.