平滑筋収縮のカルシウム感受性増強の分子機構

抄録

Rho-kinase (ROK)-mediated Ca²⁺-sensitization plays an important role in abnormal contractions of vascular smooth muscle (VSM) such as vasospasm. As an upstream mediator for this pathway, we previously identified sphingosylphosphorylcholine (SPC), which indeed induced vasospasm in vivo. The SPC-induced contraction of human VSM depended on serum total and LDL-cholesterol. Cholesterol depletion by β-cyclodextrin removed caveolin-1, a membrane raft marker, from VSM membrane and abolished the SPC-induced contraction and translocation of ROK and Fyn, a member of Src family tyrosine kinase (Src-TK). Src-TK inhibitors blocked the SPC-induced contraction and activation of ROK. Furthermore, siRNA-mediated knockdown of Fyn tyrosine kinase inhibited the SPC-induced contraction. In β-escin-permeabilized VSM, constitutively active and dominant negative Fyn induced and abolished the Ca²⁺-sensitization, respectively. The similar results were obtained with overexpression of these mutated Fyn. A functional proteomics approach identified candidate molecule and its phosphorylation site as a possible target of Fyn. These findings suggest that membrane raft and its associated Fyn tyrosine kinase plays an essential role in ROK-mediated Ca²⁺-sensitization of VSM contraction. [J Physiol Sci. 2008;58 Suppl:S32]