Characterization and differential expression of human vascular smooth muscle myosin light chain 2 isoform in nonmuscle cells.
The 20-kDa regulatory myosin light chain (MLC), also known as MLC-2, plays an important role in the regulation of both smooth muscle and nonmuscle cell contractile activity. Phosphorylation of MLC-2 by the enzyme MLC kinase increases the actin-activated myosin ATPase activity and thereby regulates the contractile activity. We have isolated and characterized an MLC-2 cDNA corresponding to the human vascular smooth muscle MLC-2 isoform from a cDNA library derived from umbilical artery RNA. The translation of the in vitro synthesized mRNA, corresponding to the cDNA insert, in a rabbit reticulocyte lysate results in the synthesis of a 20,000-dalton protein that is immunoreactive with antibodies raised against purified chicken gizzard MLC-2. The derived amino acid sequence of the putative human smooth muscle MLC-2 shows only three amino acid differences when compared to chicken gizzard MLC-2. However, comparison with the human cardiac isoform reveals only 48% homology. Blot hybridizations and S1 nuclease analysis indicate that the human smooth muscle MLC-2 isoform is expressed restrictively in smooth muscle tissues such as colon and uterus and in some, but not all, nonmuscle cell lines. Previously reported MLC-2 cDNA from rat aortic smooth muscle cells in culture is ubiquitously expressed in all muscle and nonmuscle cells, and it was suggested that both smooth muscle and nonmuscle MLC-2 proteins are identical and are probably encoded by the same gene. In contrast, the human smooth muscle MLC-2 cDNA that we have characterized from an intact smooth muscle tissue is not expressed in skeletal and cardiac muscles and also in a number of nonmuscle cells.(ABSTRACT TRUNCATED AT 250 WORDS)
Kumar
C C
CC
Department of Tumor Biology, Schering Corporation, Bloomfield, New Jersey 07003.
Mohan
S R
SR
Zavodny
P J
PJ
Narula
S K
SK
Leibowitz
P J
PJ
D000251:Adenosine Triphosphatases / Q000096:biosynthesis / Q000235:genetics*; D000595:Amino Acid Sequence; D001483:Base Sequence; D002460:Cell Line; D003001:Cloning, Molecular; D003106:Colon / Q000201:enzymology; D004247:DNA / Q000235:genetics*; D015180:Electrophoresis, Gel, Two-Dimensional; D005260:Female; D006801:Humans; D007527:Isoenzymes / Q000096:biosynthesis / Q000235:genetics*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009130:Muscle, Smooth / Q000201:enzymology*; D009131:Muscle, Smooth, Vascular / Q000201:enzymology*; D015879:Myosin Subfragments; D009218:Myosins / Q000096:biosynthesis / Q000235:genetics*; D009693:Nucleic Acid Hybridization; D010446:Peptide Fragments / Q000096:biosynthesis / Q000235:genetics*; D011247:Pregnancy; D014176:Protein Biosynthesis; D015183:Restriction Mapping; D014158:Transcription, Genetic; D014469:Umbilical Arteries / Q000201:enzymology; D014599:Uterus / Q000201:enzymology
D007527:Isoenzymes; D015879:Myosin Subfragments; D010446:Peptide Fragments; D004247:DNA; D000251:Adenosine Triphosphatases; D009218:Myosins