The role of caldesmon and its phosphorylation by ERK on the binding force of unphosphorylated myosin to actin

Abstract

Background Studies conducted at the whole muscle level have shown that smooth muscle can maintain tension with low ATP consumption. Whereas it is generally accepted that this property (latch-state) is a consequence of the dephosphorylation of myosin during its attachment to actin, free dephosphorylated myosin can also bind to actin and contribute to force maintenance. We investigated the role of caldesmon (CaD) in regulating the binding force of unphosphorylated tonic smooth muscle myosin to actin. Methods To measure the effect of CaD on the binding of unphosphorylated myosin to actin (in the presence of ATP), we used a single beam laser trap assay to quantify the average unbinding force (Funb) in the absence or presence of caldesmon, ERK-phosphorylated CaD, or CaD plus tropomyosin. Results Funb from unregulated actin (0.10 ± 0.01 pN) was significantly increased in the presence of CaD (0.17 ± 0.02 pN), tropomyosin (0.17 ± 0.02 pN) or both regulatory proteins (0.18 ± 0.02 pN). ERK phosphorylation of CaD significantly reduced the Funb (0.06 ± 0.01 pN). Inspection of the traces of the Funb as a function of time suggests that ERK phosphorylation of CaD decreases the binding force of myosin to actin or accelerates its detachment. Conclusions CaD enhances the binding force of unphosphorylated myosin to actin potentially contributing to the latch-state. ERK phosphorylation of CaD decreases this binding force to very low levels. General Significance This study suggests a mechanism that likely contributes to the latch-state and that explains the muscle relaxation from the latch-state.

Regulation of mitogen-activated protein kinase by protein kinase C and mitogen-activated protein kinase phosphatase-1 in vascular smooth muscle

“…Caldesmon is a known substrate for MAP kinase (1,20,42,56). We determined caldesmon phosphorylation levels at Ser 789 , the site catalyzed by MAP kinase.…”

Effect of Rubus idaeus L. Consumption During Pregnancy on Maternal Mice and Their Offspring

“…Polyphenols are known to have cytotoxic effects during cellular metabolism of compounds found in the extract, 27 although it depends on the type of cells that are exposed. 55 , 56 Little research has investigated the effects of chronic consumption of a polyphenol-rich diet during pregnancy on birth/fetal outcomes, and these findings further the understanding of the potential benefits and risk of RI ingestion. Because RI is rich in polyphenols, concerns have been raised about RI safety for human consumption, 57 although studies have been limited by retrospective designs with small sample size and failure to verify dose and timing of RI use.…”

Airway hyperresponsiveness; smooth muscle as the principal actor

“…Additionally, the induction of increased tone in ASM results in an increase in force generated in response to a further contractile stimulus 13 , suggesting that bronchoconstriction may beget bronchoconstriction. The maintenance of force by ASM may involve additional molecular mechanisms that affect actin-myosin interactions and potentially actin regulatory proteins such as calponin 14 and caldesmon 15 . Cytoskeletal re-organization that may not involve the classical contractile apparatus of ASM may also affect force generation, a process that is sensitive to the inhibition of Rho kinase 16 .…”