TY - JOUR
T1 - Phosphorylation of smooth muscle myosin heavy and light chains. Effects of phorbol dibutyrate and agonists
AU - Kamm, K. E.
AU - Hsu, L. C.
AU - Kubota, Y.
AU - Stull, J. T.
N1 - Copyright:
Copyright 2007 Elsevier B.V., All rights reserved.
PY - 1989
Y1 - 1989
N2 - A number of different protein kinases phosphorylate purified heavy chains or the 20-kDa light chain of smooth muscle myosin. The physiological significance of these phosphorylation reactions has been examined in intact smooth muscle. Myosin heavy chain was slightly phosphorylated (0.08 mol of phosphate/mol) under control conditions in bovine tracheal tissue. Treatment with carbachol, isoproterenol, or phorbol 12,13-dibutyrate resulted in no significant change. In contrast, heavy chain was phorphorylated to 0.30 mol of phosphate/mol of heavy chain in tracheal smooth muscle cells in culture. This value increased significantly with ionomycin treatment. In control tissues, 9% of the light chain was monophosphorylated with 32P in the serine site phosphorylated by myosin light chain kinase. Carbachol (0.1 μM) alone resulted in contraction and 42% monophosphorylated light chain with 32P only in the serine site phosphorylated by myosin light chain kinase. Similarly, stimulation with histamine, 5-hydroxytryptamine, or KCl resulted in 32P incorporation into only the myosin light chain kinase serine site. Phorbol 12,13-dibutyrate (1 μM) alone resulted in 22% monophosphorylated light chain. However, only 25% of the 32P was in the myosin light chain kinase serine site, whereas 75% was in a serine site phosphorylated by protein kinase C. Phorbol 12,13-dibutyrate plus carbachol resulted in 27% monophosphorylated light chain; 75% of the 32P was in the myosin light chain kinase serine site, with the remainder in the protein kinase C serine site. These results indicate that phorbol esters act to increase phosphorylation of myosin light chain by protein kinase C. However, receptor-mediated stimulation or depolarization leading to tracheal smooth muscle contraction results in phosphorylation of myosin light chain by myosin light chain kinase alone.
AB - A number of different protein kinases phosphorylate purified heavy chains or the 20-kDa light chain of smooth muscle myosin. The physiological significance of these phosphorylation reactions has been examined in intact smooth muscle. Myosin heavy chain was slightly phosphorylated (0.08 mol of phosphate/mol) under control conditions in bovine tracheal tissue. Treatment with carbachol, isoproterenol, or phorbol 12,13-dibutyrate resulted in no significant change. In contrast, heavy chain was phorphorylated to 0.30 mol of phosphate/mol of heavy chain in tracheal smooth muscle cells in culture. This value increased significantly with ionomycin treatment. In control tissues, 9% of the light chain was monophosphorylated with 32P in the serine site phosphorylated by myosin light chain kinase. Carbachol (0.1 μM) alone resulted in contraction and 42% monophosphorylated light chain with 32P only in the serine site phosphorylated by myosin light chain kinase. Similarly, stimulation with histamine, 5-hydroxytryptamine, or KCl resulted in 32P incorporation into only the myosin light chain kinase serine site. Phorbol 12,13-dibutyrate (1 μM) alone resulted in 22% monophosphorylated light chain. However, only 25% of the 32P was in the myosin light chain kinase serine site, whereas 75% was in a serine site phosphorylated by protein kinase C. Phorbol 12,13-dibutyrate plus carbachol resulted in 27% monophosphorylated light chain; 75% of the 32P was in the myosin light chain kinase serine site, with the remainder in the protein kinase C serine site. These results indicate that phorbol esters act to increase phosphorylation of myosin light chain by protein kinase C. However, receptor-mediated stimulation or depolarization leading to tracheal smooth muscle contraction results in phosphorylation of myosin light chain by myosin light chain kinase alone.
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M3 - Article
C2 - 2592371
AN - SCOPUS:0024791474
SN - 0021-9258
VL - 264
SP - 21223
EP - 21229
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 35
ER -