Calponin reduces shortening velocity in skinned taenia coli smooth muscle fibres

Jaworowski, Åsa; Anderson, Kurt I.; Arner, Anders; Engström, Martin; Gimona, Mario; Strasser, Peter; Small, J. Victor

doi:10.1016/0014-5793(95)00451-e

Cited by 53 publications

(35 citation statements)

References 30 publications

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“…This suggests that calponin has only a slight effect on the binding of the myosin head to actin; instead it affects primarily the ratelimiting step (presumably corresponding to the weak to strong transition). Furthermore, calponin inhibited maximal shortening velocity with only a minor effect on force in skinned Taenia coli smooth muscle fibers (40). In the in vitro motility assay, calponin decreased the fraction of motile actin filaments (34,41), which was also observed with troponin and caldesmon, both known to inhibit by blocking the strong binding state (42,43).…”

Section: Discussionmentioning

confidence: 82%

The Effects of Smooth Muscle Calponin on the Strong and Weak Myosin Binding Sites of F-actin

El-Mezgueldi

Marston

1996

Journal of Biological Chemistry

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We have investigated the mechanism of inhibition of the actomyosin MgATPase by the smooth muscle protein calponin. We have shown previously the specific interaction of calponin with Glu 334 of actin (EL-Mezgueldi, M., Fattoum, A., Derancourt, J., and Kassab, R. (1992) J. Biol. Chem. 267, 15943-15951). This residue is within the sequence 332-334, which has been proposed to be an important part of the strong myosin binding site (Rayment, I., Holden, H. M., Whittaker, M., Yohn, C. B., Lorenz, M., Holmes, K. C., and Milligan, R. A. (1993) Science 261, 58 -65). Therefore, we suggested that calponin will affect the strong binding actin-myosin interaction. To test this hypothesis we have investigated the effect of calponin on the strong binding of S-1⅐MgAMP-PNP (5-adenylyl imidodiphosphate) and on the weak binding of S-1⅐MgADP⅐P i to actin. We found that an inhibitory concentration of calponin decreased the binding of S-1⅐MgAMP-PNP to actin but had no effect on the binding of S-1⅐MgADP⅐P i . Similar results were obtained with skeletal muscle and smooth muscle S-1. In competition experiments calponin was found to displace S-1⅐MgAMP-PNP and S-1⅐MgADP but not S-1⅐MgADP⅐P i from the actin filament. S-1 displaced calponin from actin in the rigor state, in the presence of MgADP, and in the presence of MgAMP-PNP. We conclude that calponin inhibits the actin activated S-1 ATPase by blocking a strong S-1 binding site on actin and does not block the weak binding site.

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Section: Discussionmentioning

confidence: 82%

The Effects of Smooth Muscle Calponin on the Strong and Weak Myosin Binding Sites of F-actin

El-Mezgueldi

Marston

1996

Journal of Biological Chemistry

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“…Since nonspecific binding of excess calponin to the thin filaments of skinned smooth muscle can inhibit shortening velocity and force (29,30), we sought to assess the regulatory properties of T18A͞S19A RLC and dephosphorylated WT RLC without perturbing the endogenous calponin. This was achieved by exchanging RLCs at elevated temperature in the absence of divalent cations, similar to procedures used for skinned striated muscle or in solution with purified myosin (31).…”

Section: Resultsmentioning

confidence: 99%

Slow cycling of unphosphorylated myosin is inhibited by calponin, thus keeping smooth muscle relaxed

Malmqvist

Trybus

Yagi

et al. 1997

Proc. Natl. Acad. Sci. U.S.A.

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A key unanswered question in smooth muscle biology is whether phosphorylation of the myosin regulatory light chain (RLC) is sufficient for regulation of contraction, or if thin-filament-based regulatory systems also contribute to this process. To address this issue, the endogenous RLC was extracted from single smooth muscle cells and replaced with either a thiophosphorylated RLC or a mutant RLC (T18A͞ S19A) that cannot be phosphorylated by myosin light chain kinase. The actin-binding protein calponin was also extracted. Following photolysis of caged ATP, cells without calponin that contained a nonphosphorylatable RLC shortened at 30% of the velocity and produced 65% of the isometric force of cells reconstituted with the thiophosphorylated RLC. The contraction of cells reconstituted with nonphosphorylatable RLC was, however, specifically suppressed in cells that contained calponin. These results indicate that calponin is required to maintain cells in a relaxed state, and that in the absence of this inhibition, dephosphorylated cross-bridges can slowly cycle and generate force. These findings thus provide a possible framework for understanding the development of latch contraction, a widely studied but poorly understood feature of smooth muscle.

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“…ponin was reported to reduce unloaded isometric forces and shortening velocity (8,14,19,23) by the inhibition of actomyosin ATPase activity in a reconstituted isolated filament system (26). On the other hand, there have been several studies suggesting that calponin increases the contractile response to norepinephrine (NE) (18) or phenylephrine (PE) (9,16,20) by facilitating agonist-induced signal transduction.…”

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confidence: 99%

Enhanced baroreflex sensitivity in free-moving calponin knockout mice

Masuki¹,

Takeoka

Taniguchi

et al. 2003

American Journal of Physiology-Heart and Circulatory Physiology

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Masuki, Shizue, Michiko Takeoka, Shun'ichiro Taniguchi, and Hiroshi Nose. Enhanced baroreflex sensitivity in free-moving calponin knockout mice. Am J Physiol Heart Circ Physiol 284: H939-H946, 2003. First published November 14, 2002 10.1152/ajpheart.00610.2002Calponin is an actin binding protein in vascular smooth muscle that modifies contractile responses. However, its role in mean arterial pressure (MAP) regulation has not been clarified. To assess this, MAP and heart rate (HR) were measured in calponin knockout (KO) mice, and the results were compared with those in wild-type (WT) mice. The measurements were performed every 100 ms during a 60-min free-moving state each day for 3 days. Mice in both groups rested during ϳ70% of the total measuring period. The mean HR during rest was significantly lower in KO mice than in WT mice but with no significant difference in MAP between the groups. The change in HR response (⌬HR) to spontaneous change in MAP (⌬MAP) varied in a wider range in KO mice with an 80% increase in the coefficient of variation for HR (P Ͻ 0.05), whereas MAP in KO mice was controlled in a narrow range similar to that in WT mice. The baroreflex sensitivity (⌬HR/ ⌬MAP), determined from the change in HR to the spontaneous change in MAP, was twofold higher in KO mice than that in WT mice (P Ͻ 0.01), whereas there were no significant differences in the baroreflex sensitivity determined by intravascular administration of phenylephrine and sodium nitroprusside between the two groups (P Ͼ 0.1). The MAP response to the administrated doses of phenylephrine in KO mice was reduced to one-half of that in WT mice (P Ͻ 0.01) but with no significant difference in the response to sodium nitroprusside between the groups. The differences in HR variability and the spontaneous baroreflex sensitivity between the two groups completely disappeared after carotid sinus denervation. These results suggest that the higher variability in HR for KO mice was caused by the increased spontaneous arterial baroreflex sensitivity, though not detected by the intra-arterial administration of the drug, and that the higher variability of HR may be a compensatory adaptation to the blunted ␣-adrenergic response of peripheral vessels to sympathetic nervous activity.carotid sinus denervation; heart rate variability CALPONIN, also called basic calponin or calponin H1, was first isolated from the chicken gizzard as an actinbinding protein, which was reported to be involved in the regulation of smooth muscle contraction (22). Calponin was reported to reduce unloaded isometric forces and shortening velocity (8,14,19,23) by the inhibition of actomyosin ATPase activity in a reconstituted isolated filament system (26). On the other hand, there have been several studies suggesting that calponin increases the contractile response to norepinephrine (NE) (18) or phenylephrine (PE) (9,16,20) by facilitating agonist-induced signal transduction.With the exception of these in vitro studies, however, there have been few studies investigating the role of cal...

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Calponin reduces shortening velocity in skinned taenia coli smooth muscle fibres

Cited by 53 publications

References 30 publications

The Effects of Smooth Muscle Calponin on the Strong and Weak Myosin Binding Sites of F-actin

The Effects of Smooth Muscle Calponin on the Strong and Weak Myosin Binding Sites of F-actin

Slow cycling of unphosphorylated myosin is inhibited by calponin, thus keeping smooth muscle relaxed

Enhanced baroreflex sensitivity in free-moving calponin knockout mice

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