Garde J, Roldan E R
Department of Development and Signalling, Babraham Institute, Cambridge, UK.
FEBS Lett. 1996 Aug 12;391(3):263-8. doi: 10.1016/0014-5793(96)00749-1.
Acrosomal exocytosis triggered with A23187/Ca2+ was enhanced by rab3AL, a synthetic peptide corresponding to the effector domain of the small GTP-binding protein rab3. Exocytosis was further enhanced when spermatozoa were also exposed to dibutyryl-cAMP, but was prevented when H-89, a protein kinase A (PKA) inhibitor, was included. The action of rab3AL was not on, or upstream of, phospholipase A2 (PLA2). Inhibition of exocytosis by the PLA2 inhibitor aristolochic acid was overcome by rab3AL when it was included together with lysophosphatidylcholine; this effect was prevented by H-89. These results suggest a functional coupling between rab3 protein, metabolites generated by PLA2, and cAMP-activated PKA, in the final steps leading to membrane fusion during acrosomal exocytosis.
用A23187/Ca2+触发的顶体胞吐作用，可被rab3AL增强，rab3AL是一种与小GTP结合蛋白rab3的效应结构域相对应的合成肽。当精子也暴露于二丁酰环磷腺苷时，胞吐作用进一步增强，但当加入蛋白激酶A（PKA）抑制剂H-89时，胞吐作用受到抑制。rab3AL的作用不在磷脂酶A2（PLA2）上，也不在其上游。当rab3AL与溶血磷脂酰胆碱一起加入时，PLA2抑制剂马兜铃酸对胞吐作用的抑制被rab3AL克服；H-89可阻止这种效应。这些结果表明，在顶体胞吐过程中导致膜融合的最后步骤中，rab3蛋白、PLA2产生的代谢产物和cAMP激活的PKA之间存在功能偶联。
