Mystixin-7 and Mystixin-11 Increase Cytosolic Free Ca-2+ and InositolTrisphosphates in Human A-431 Cells

摘要

Mystixin-7 and mystixin. II. small peptides structurally related to cortiootropin-releasing factor (CRF). have been shown to attenuate vascular leakage in injured skin. The goal of this study was to characterize changes in cytosolic Ca2+ concentration (Ca2+) in human epidermoid AAtl cells treated with these two peptides and to investigate the remechanisms by which these changes occur. The resting (Caa) in AA3l cells at 37%C Was 76-2 nM (n -373). When cells were treated with either peptide. (Ca2+) increased immediately. The increase depended on the peptide concentration with a meedian effective concentration of 299-9 pM for n-stixia-7 and 23 0.04 pM for mystixin-I 1. The increases also depnded on extracellular Ca:+ and were blocked by Cd'+. Co'%. verapamil and nifedipine a.Helical CRF<9%l). a synthetic CRF receptor antagonist and pertussis toxin also blocked the increase in Ca'+% induced by the two peptide taken together. These results suggest that mystixin-7 and mystixin.l I interact with Clur receptors to activate pertussis-sensitive C; proteins coupled to L-type Ca2+ channels that allow an uptake of extracellular Ca'+. Because U.7312Z an Inhibitor of inositol trisphosphate production partially inhibited the Increase in C;a2+.) we increased inositol trisphosphates in cells stimulated by the two peptides. Both increased inositol trisphosphate leveis' within 1 min. The increase WM inhibited by the removal of extracellular Ca or treatment with U.73 1 2% The results suggest that the C;a2+ influx' stimulated by mystixin-7 and mystixin II induces an increase in inositol trisphosphates. resulting in a mobilization of Ca'% from lA,5.lnositol trisphosphate-sensitive Ca%% pools.