Injected inositol 1,4,5‐trisphosphate activates Ca2+ ‐sensitive K + channels in the plasmalemma of Eremosphaera viridis

[摘要]

InsP₃, an established mediator of intracellular Ca²⁺ signals in animal cells, is microinjected into the cytoplasm of Eremosphaera viridis. InsP₃, but not Ins, InsP₁, InsP₂ or F2,6-P₂ induce a transient opening of Ca²⁺ -dependent K⁺ channels in the plasmalemma of this alga. This effect is indicated by a transient polarization (TP) with a simultaneous increase of membrane conductance. The TP is inhibited by TMB₈ (2 mM), an intracellular Ca²⁺ antagonist or by BAPTA (20 mM), microinjected together with InsP₃. The results suggest that InsP₃ initiates an increase in the cytoplasmic Ca²⁺ activity and an activation of Ca²⁺-dependent membrane currents, hence, opening of K⁺ channels.

[学科分类] 生物化学/生物物理

[关键词] InsP3;K+ channel;Ca2+ -dependent;Transient potential;Eremosphaera viridis;BAPTA;bis-(o-aminophenoxy)-ethane N;N;N';N' tetraacetic acid;E K;Nernst potential of potassium;E m;membrane potential;ER;endoplasmic reticulum;F2;6-P2;fructose 2;6-bisphosphate;Ins;myo-inositol;InsP1;myo-inositol 2-monophosphate;InsP2;myo-inositol 1;4-bisphosphate;InsP3;myo-inositol 1;4;5-trisphosphate;TEA;tetraethylammonium;TMB8;3;4;5-trimethoxybenzoic acid 8-diethylaminooctyl ester;TP;transient potential