Ca2+, cAMP, and changes in myosin phosphorylation during contraction of smooth muscle.

M. O. Aksoy, S. Mras, K. E. Kamm, R. A. Murphy

Research output: Contribution to journalArticle

57 Citations (Scopus)

Abstract

Phosphorylation of myosin increases rapidly upon stimulation of an arterial smooth muscle. However, peak values are not maintained and phosphorylation declines, while active stress increases monotonically to a sustained steady state. The aim of this study was to determine the reason(s) for the transient change in myosin phosphorylation. Four hypotheses were considered: 1) reduced substrate, i.e., ATP depletion, 2) altered access of either the myosin kinase or phosphatase to the cross bridge, 3) reduced myosin kinase activity secondary to its phosphorylation by adenosine 3',5'-cyclic monophosphate-dependent protein kinase, and 4) reduced myoplasmic [Ca2+] during the contraction. Our results suggest that the most likely explanation is that there are two Ca2+-dependent regulatory processes: 1) myosin phosphorylation and 2) a second, unidentified site allowing stress maintenance with reduced cross-bridge cycling rates. A higher cell Ca2+ concentration appears to be necessary to activate myosin kinase and produce myosin phosphorylation than is needed for force maintenance. We suggest that agonist-induced Ca2+ transients, coupled with the differential Ca2+ sensitivity of the two regulatory systems, may explain the observed transient in myosin phosphorylation during a maintained contraction in smooth muscle.

Original languageEnglish (US)
JournalThe American journal of physiology
Volume245
Issue number3
StatePublished - Sep 1983

Fingerprint

Myosins
Smooth Muscle
Phosphorylation
Myosin-Light-Chain Kinase
Myosin-Light-Chain Phosphatase
Maintenance
Cyclic AMP
Protein Kinases
Adenosine Triphosphate

ASJC Scopus subject areas

  • Medicine(all)

Cite this

Ca2+, cAMP, and changes in myosin phosphorylation during contraction of smooth muscle. / Aksoy, M. O.; Mras, S.; Kamm, K. E.; Murphy, R. A.

In: The American journal of physiology, Vol. 245, No. 3, 09.1983.

Research output: Contribution to journalArticle

@article{6b4a60999fec48eaa0fa555d69c18b6b,
title = "Ca2+, cAMP, and changes in myosin phosphorylation during contraction of smooth muscle.",
abstract = "Phosphorylation of myosin increases rapidly upon stimulation of an arterial smooth muscle. However, peak values are not maintained and phosphorylation declines, while active stress increases monotonically to a sustained steady state. The aim of this study was to determine the reason(s) for the transient change in myosin phosphorylation. Four hypotheses were considered: 1) reduced substrate, i.e., ATP depletion, 2) altered access of either the myosin kinase or phosphatase to the cross bridge, 3) reduced myosin kinase activity secondary to its phosphorylation by adenosine 3',5'-cyclic monophosphate-dependent protein kinase, and 4) reduced myoplasmic [Ca2+] during the contraction. Our results suggest that the most likely explanation is that there are two Ca2+-dependent regulatory processes: 1) myosin phosphorylation and 2) a second, unidentified site allowing stress maintenance with reduced cross-bridge cycling rates. A higher cell Ca2+ concentration appears to be necessary to activate myosin kinase and produce myosin phosphorylation than is needed for force maintenance. We suggest that agonist-induced Ca2+ transients, coupled with the differential Ca2+ sensitivity of the two regulatory systems, may explain the observed transient in myosin phosphorylation during a maintained contraction in smooth muscle.",
author = "Aksoy, {M. O.} and S. Mras and Kamm, {K. E.} and Murphy, {R. A.}",
year = "1983",
month = "9",
language = "English (US)",
volume = "245",
journal = "American Journal of Physiology - Heart and Circulatory Physiology",
issn = "0363-6135",
publisher = "American Physiological Society",
number = "3",

}

TY - JOUR

T1 - Ca2+, cAMP, and changes in myosin phosphorylation during contraction of smooth muscle.

AU - Aksoy, M. O.

AU - Mras, S.

AU - Kamm, K. E.

AU - Murphy, R. A.

PY - 1983/9

Y1 - 1983/9

N2 - Phosphorylation of myosin increases rapidly upon stimulation of an arterial smooth muscle. However, peak values are not maintained and phosphorylation declines, while active stress increases monotonically to a sustained steady state. The aim of this study was to determine the reason(s) for the transient change in myosin phosphorylation. Four hypotheses were considered: 1) reduced substrate, i.e., ATP depletion, 2) altered access of either the myosin kinase or phosphatase to the cross bridge, 3) reduced myosin kinase activity secondary to its phosphorylation by adenosine 3',5'-cyclic monophosphate-dependent protein kinase, and 4) reduced myoplasmic [Ca2+] during the contraction. Our results suggest that the most likely explanation is that there are two Ca2+-dependent regulatory processes: 1) myosin phosphorylation and 2) a second, unidentified site allowing stress maintenance with reduced cross-bridge cycling rates. A higher cell Ca2+ concentration appears to be necessary to activate myosin kinase and produce myosin phosphorylation than is needed for force maintenance. We suggest that agonist-induced Ca2+ transients, coupled with the differential Ca2+ sensitivity of the two regulatory systems, may explain the observed transient in myosin phosphorylation during a maintained contraction in smooth muscle.

AB - Phosphorylation of myosin increases rapidly upon stimulation of an arterial smooth muscle. However, peak values are not maintained and phosphorylation declines, while active stress increases monotonically to a sustained steady state. The aim of this study was to determine the reason(s) for the transient change in myosin phosphorylation. Four hypotheses were considered: 1) reduced substrate, i.e., ATP depletion, 2) altered access of either the myosin kinase or phosphatase to the cross bridge, 3) reduced myosin kinase activity secondary to its phosphorylation by adenosine 3',5'-cyclic monophosphate-dependent protein kinase, and 4) reduced myoplasmic [Ca2+] during the contraction. Our results suggest that the most likely explanation is that there are two Ca2+-dependent regulatory processes: 1) myosin phosphorylation and 2) a second, unidentified site allowing stress maintenance with reduced cross-bridge cycling rates. A higher cell Ca2+ concentration appears to be necessary to activate myosin kinase and produce myosin phosphorylation than is needed for force maintenance. We suggest that agonist-induced Ca2+ transients, coupled with the differential Ca2+ sensitivity of the two regulatory systems, may explain the observed transient in myosin phosphorylation during a maintained contraction in smooth muscle.

UR - http://www.scopus.com/inward/record.url?scp=0020823615&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0020823615&partnerID=8YFLogxK

M3 - Article

C2 - 6311024

AN - SCOPUS:0020823615

VL - 245

JO - American Journal of Physiology - Heart and Circulatory Physiology

JF - American Journal of Physiology - Heart and Circulatory Physiology

SN - 0363-6135

IS - 3

ER -