Effects of a synthetic peptide of heat shock protein 20 on the contractile response and the myosin light chain phosphorylation of skinned phasic smooth muscle.

Abstract

Heat shock protein 20 (HSP20) has actin binding capacity and its amino acid sequence of actin binding region (residue 110-121) is highly homogenous to the inhibitory region of skeletal muscle troponin I (residue 104-115; TnIp). Recent studies reported contribution of HSP20 phosphorylation in cGMP-induced relaxation, and force inhibiting effects of a syntetic peptide of HSP20 (residue 110-121; HSP20_p) on tonic vascular skinned smooth muscle (Rembold et al., 2000). To elucidate the role of HSP20_p on the phasic smooth muscle, we studied the effects of HSP20_p on contractile properties of Triton-X-100 skinned muscle preparations from guinea pig taenia caeci. In Ca²⁺ induced contraction, HSP20_p enhanced Ca²⁺ sensitivity for the force, although HSP20_p slightly inhibited the maximal Ca²⁺ induced force. Also HSP20_p enhanced Ca²⁺ induced posphorylation of myosin regulatory light chain (MLC20). On the other hand, HSP20_p inhibited the myosin phosporylation independent contraction by 30 mM Mg²⁺. Our present results suggest that, in phasic smooth muscles, HSP20_p may affect both thick filament linked- and thin filament linked-regulation of contraction. [Jpn J Physiol 54 Suppl:S124 (2004)]