High impact information on Actn

• Kettin is a high molecular mass protein of insect muscle that in the sarcomeres binds to actin and alpha-actinin [1].
• Digestion of kettin may cause disintegration of the Z-disc and alpha-actinin release which lead to disassembly of the myofibril [2].
• An expressed class II domain with flanking linker sequences binds to actin and alpha-actinin but not to myosin [2].
• The Ca2+ activated protease, calpain, disrupts the Z-disc of striated muscle, releasing alpha-actinin intact [2].
• Perturbations of Drosophila alpha-actinin cause muscle paralysis, weakness, and atrophy but do not confer obvious nonmuscle phenotypes [3].

Biological context of Actn

• We discuss these phenotypes in the light of presumed in vivo alpha-actinin functions [4].
• Molecular genetics of Drosophila alpha-actinin: mutant alleles disrupt Z disc integrity and muscle insertions [4].
• Allelic but less severely affected fliA mutants are apparently due to point mutations, and develop into adults having thoracic muscle abnormalities [4].
• In all four cases, hemizygous mutants complete embryogenesis and do not die until the second day of larval growth, signifying that either the role of alpha-actinin in nonmuscle cells is redundant or that a distinct and only distantly related gene encodes the non-muscle isoform [4].
• Successful rescue indicated that alternative splicing, which also generates larval muscle and non-muscle isoforms, was not essential for viability and that there were no strict spatial or temporal requirements for alpha-actinin expression [5].

Anatomical context of Actn

• In ovaries, non-muscle alpha-actinin was localized in the nurse cell subcortical cytoskeleton, cytoplasmic actin cables and ring canals [6].
• We found that non-muscle alpha-actinin was present in young embryos and in the embryonic central nervous system [6].
• In the mutant, alpha-actinin expression remained in muscle tissues, but also in a subpopulation of epithelial cells in both embryos and ovaries [6].
• Immunolabeling studies on the rabbit psoas muscle demonstrated that antigenicity of alpha-actinin was retained in Epon-extracted sections [7].
• It is known that non-muscle (NM) and smooth muscle (SM) exons of the rat alpha-actinin gene are used in a mutually exclusive manner [8].

Associations of Actn with chemical compounds

• Consistent with this observation, alpha-actinin and other high molecular weight proteins, possibly associated with Z-discs, are not detected on SDS/polyacrylamide gels or Western blots of skinned adult IFM [9].
• Histochemical analysis revealed clusters of integrin together with phosphotyrosine and alpha-actinin [10].

Co-localisations of Actn

• RESULTS AND CONCLUSIONS: In the first step of assembly, projectin immunolocalization appears as random aggregates colocalizing with alpha-actinin, kettin and Z(210), as well as, F-actin [11].

Regulatory relationships of Actn

• First, we tested the ability of a cDNA-based transgene encoding the adult muscle isoform of alpha-actinin under control of the heterologous ubiquitin promoter to rescue the lethality of null alpha-actinin mutations [5].
• Drosophila alpha-actinin in ovarian follicle cells is regulated by EGFR and Dpp signalling and required for cytoskeletal remodelling [12].

Other interactions of Actn

• Thirdly, the length of alpha-actinin was modified by adding a 114 amino acid structural repeat from alpha-spectrin to the center of the rod domain of alpha-actinin [5].
• Analysis of mutations that affect expression of integrins and alpha-actinin, key components of these structures, also failed to perturb Mlp84B distribution [13].
• Sequence similarity of the amino-terminal domain of Drosophila beta spectrin to alpha actinin and dystrophin [14].
• On Lowicryl sections of asynchronous flight muscle, indirect immunogold staining has localized alpha-actinin and the 210-kD protein throughout the matrix of the Z-band, projectin between the Z- and A-bands, and the 400/600-kD components at the I-band/Z-band junction [15].
• Spectrin and the related proteins dystrophin and alpha-actinin consist largely of repeated motifs of 100-120 residues [16].

References