And carbachol were similar, but the rate of force relaxation was reduced (Guo et al., 2013). In contrast to these results, an siRNA-induced decrease in caldesmon expression lowered both isometric force and muscle shortening velocity (Smolock et al., 2009). In cultured smooth muscle cells, p42/44 MAPK has been clearly demonstrated to phosphorylate caldesmon at Ser789 (Hedges et al., 2000), but for