A role for MAP kinase in differentiated smooth muscle contraction evoked by α-adrenoceptor stimulation

Abstract

The purpose of this study was to investigate the potential role of mitogen-activated protein (MAP) kinase in smooth muscle contraction by monitoring MAP kinase activation, caldesmon phosphorylation, and contractile force during agonist stimulation. Isometric tension in response to KCl and phenylephrine (PE) was measured from strips of ferret aorta. MAP kinase activation was monitored by Western blot using a phosphospecific p44/p42 MAP kinase antibody. Caldesmon phosphorylation was assessed using specific phosphocaldesmon antibodies. We report here that treatment of smooth muscle strips with PD-098059, a specific inhibitor of MAP kinase kinase, did not detectably modify the KCl-evoked contraction but significantly inhibited the contraction to PE in the absence of extracellular Ca2+. In this experimental condition, where the contraction occurs in the absence of increases in 20-kDa myosin light chain phosphorylation, PD-098059 also inhibited significantly MAP kinase and caldesmon phosphorylation. Collectively, these results demonstrate a direct cause-and-effect relationship between MAP kinase activation and Ca2+-independent smooth muscle contraction and support the concept of caldesmon phosphorylation as the missing link between both events.

Focal adhesion signaling is required for myometrial ERK activation and contractile phenotype switch before labor

“…After activation, ERK undergoes a second redistribution to the contractile filament to meet up with its substrate, CaD [Khalil et al, 1995]. ERK-mediated phosphorylation of CaD is known to dis-inhibit actomyosin interactions in vascular muscle [Dessy et al, 1998] and in vitro [Foster et al, 2004]. In the present study we found that a similar translocation of ERK from the cytosol to the surface membrane occurs in late pregnancy in myometrial cells (Fig.…”

Regulation of Vascular Smooth Muscle Tone by N-terminal Region of Caldesmon

“…However, as described above, the PE-induced contraction at constant [Ca 2ϩ ] i is thought to result in alleviation of the inhibitory effect of C-terminal caldesmon on actin-activated myosin ATPase activity, possibly by phosphorylation of the C-terminal of caldesmon by MAPK (35)(36) (Fig. 10B).…”

“…3B1). We have previously shown that ferret portal vein and aortic cells contract in response to PE at near resting [Ca 2ϩ ] i levels in the absence of changes in LC 20 phosphorylation, and this contraction is associated with activation of protein kinase C and mitogen-activated protein kinase (MAPK) and phosphorylation of the C-terminal half of caldesmon (29,(33)(34)(35)(36). In contrast, it is known that microcystin-LR is an inhibitor of myosin light chain phosphatase that causes contraction by increasing LC 20 phosphorylation levels (37).…”

“…Another major finding of the present study was that pretreatment of the cells with IK29C inhibited PE-induced contractions but not microcystin-LR-induced contractions. It has previously been reported that the ␣-adrenergic agonist, PE, elicits a contraction in ferret vascular smooth muscle cells, and this contraction is associated with phosphorylation of the Cterminal domain of caldesmon by activation of protein kinase C and MAPK (2,(35)(36)43). Conversely, microcystin-LR is known to be an inhibitor of myosin light chain phosphatase and to contract smooth muscle in the absence of changes in [Ca 2ϩ ] i by increasing LC 20 phosphorylation (37).…”

Extracellular signal‐regulated kinase 1/2 control Ca2+‐independent force development in histamine‐stimulated bovine tracheal smooth muscle

“…Second, puri®ed caldesmon is phosphorylated by ERK-2 in a cell-free system and addition of ERK-2 to Triton X-100-permeabilized canine airways smooth muscle ®bres potentiates Ca 2+ -induced tension development (Gerthoer et al, 1997). Third, caldesmon is phosphorylated in intact airways, gastrointestinal and vascular smooth muscle during agonist-induced contraction (Dessy et al, 1998;Gerthoer et al, 1996;Gerthoer & Pohl, 1994) at proline-directed serines (i.e. S 789 PTKV and S 759 PAPK), which is characteristic of a mitogen-activated protein (MAP) kinase consensus sequence (Adam & Hathaway, 1993).…”