Vertebrates have conserved capping protein alpha isoforms with specific expression patterns.
Capping protein (CP), a ubiquitous actin binding protein composed of an alpha and a beta subunit, is important for actin assembly and cell motility. Lower organisms have one gene and one isoform of each subunit. Chickens have two very similar alpha-subunit isoforms. To determine if vertebrates in general contain multiple alpha isoforms and if those alpha isoforms have conserved sequences, we isolated and analyzed alpha subunit cDNA's in mice and humans. Both mice and humans also have two alpha isoforms. Phylogenetic analysis of the alpha isoform sequences reveals that vertebrates have two highly conserved subfamilies, alpha1 and alpha2. The alpha1 and alpha2 subfamilies are very similar to each other but can be defined and distinguished from each other by a small number of key amino acid residues. In addition, 3' untranslated cDNA sequences are conserved within the isoform subfamilies. To investigate the function of the alpha isoforms, we examined their expression in mouse cells and tissues. Endothelial cells contain only the alpha2 isoform, and erythrocytes contain almost exclusively the alpha1 isoform. Most tissues have both alpha1 and alpha2 isoforms but the ratio of alpha1:alpha2 varies widely. Together, these findings support the hypothesis that the CP alpha isoforms have conserved, unique and essential roles in vertebrates.
Hart
M C
MC
Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA. mhart@cellbio.wustl.edu
Korshunova
Y O
YO
Cooper
J A
JA
D051339:Actin Depolymerizing Factors; D000199:Actins / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D051347:CapZ Actin Capping Protein; D002478:Cells, Cultured; D003001:Cloning, Molecular; D051345:Destrin; D019143:Evolution, Molecular; D006801:Humans; D015151:Immunoblotting; D051379:Mice; D008840:Microfilament Proteins / Q000235:genetics* / Q000378:metabolism*; D008969:Molecular Sequence Data; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014018:Tissue Distribution
D051339:Actin Depolymerizing Factors; D000199:Actins; C495842:CAPZA1 protein, human; C495845:CAPZA2 protein, human; D051347:CapZ Actin Capping Protein; C495843:Capza1 protein, mouse; C495847:Capza2 protein, mouse; D051345:Destrin; D008840:Microfilament Proteins