Characterization of a novel cofilin isoform that is predominantly expressed in mammalian skeletal muscle.
Cofilin is an actin-modulating protein of 20 kDa, which is widely distributed throughout muscle and non-muscle cells. By means of immunoblotting combined with two-dimensional gel electrophoresis, we found that two cofilin variants, muscle type (M-type) and non-muscle type (NM-type), exist in mammals, while a single isoform exists in chickens. During in vitro myogenesis of mouse C2 cells, expression of the M-type cofilin was upregulated. To better understand the nature of the M-type cofilin, we cloned cDNAs encoding M-type cofilin from the cDNA library of C2 myotubes and determined the entire sequence. The deduced peptide sequence contained a nuclear localization signal and a putative actin-binding sequence as reported in NM-type cofilin. The sequence showed 81% identity in the amino acid residues with the mouse NM-type cofilin sequence and, interestingly, higher homology (96% identity) with that of chicken cofilin. The mRNA encoding M-type cofilin, though it contains two variants that differ in the size of their 3'-non-coding sequences, was detected predominantly in heart, skeletal muscle, C2 myotubes, and testis by Northern blotting, while the mRNA for NM-type cofilin was seen in a variety of non-muscle tissues. The presence of the muscle type isoform of cofilin strongly suggests that cofilin is deeply involved in the regulation of actin function not only in non-muscle cells but also in muscle cells.
Ono
S
S
Graduate School of Science and Technology, Chiba University, Japan.
Minami
N
N
Abe
H
H
Obinata
T
T
D016475:3T3 Cells; D051339:Actin Depolymerizing Factors; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D015139:Blotting, Southern; D002478:Cells, Cultured; D002642:Chick Embryo; D003001:Cloning, Molecular; D051340:Cofilin 2; D018076:DNA, Complementary; D015180:Electrophoresis, Gel, Two-Dimensional; D051379:Mice; D008807:Mice, Inbred BALB C; D008840:Microfilament Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009132:Muscles / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017386:Sequence Homology, Amino Acid
D051339:Actin Depolymerizing Factors; C495816:Cfl2 protein, mouse; D051340:Cofilin 2; D018076:DNA, Complementary; D008840:Microfilament Proteins; D009419:Nerve Tissue Proteins; D012333:RNA, Messenger