López José J, Camello-Almaraz Cristina, Pariente José A, Salido Ginés M, Rosado Juan A
Department of Physiology, University of Extremadura, 10071 Cáceres, Spain.
Biochem J. 2005 Aug 15;390(Pt 1):243-52. doi: 10.1042/BJ20050168.
Most physiological agonists increase cytosolic free [Ca2+]c (cytosolic free Ca2+ concentration) to regulate a variety of cellular processes. How different stimuli evoke distinct spatiotemporal Ca2+ responses remains unclear, and the presence of separate intracellular Ca2+ stores might be of great functional relevance. Ca2+ accumulation into intracellular compartments mainly depends on the activity of Ca2+- and H+-ATPases. Platelets present two separate Ca2+ stores differentiated by the distinct sensitivity to thapsigargin and TBHQ [2,5-di-(t-butyl)-1,4-hydroquinone]. Although one store has long been identified as the dense tubular system, the nature of the TBHQ-sensitive store remains uncertain. Treatment of platelets with GPN (glycylphenylalanine-2-naphthylamide) impaired Ca2+ release by TBHQ and reduced that evoked by thrombin. In contrast, GPN did not modify Ca2+ mobilization stimulated by ADP or AVP ([arginine]vasopressin). Treatment with nigericin, a proton carrier, and bafilomycin A1, an inhibitor of the vacuolar H+-ATPase, to dissipate the proton gradient into acidic organelles induces a transient increase in [Ca2+]c that was abolished by previous treatment with the SERCA (sarcoplasmic/endoplasmic-reticulum Ca2+-ATPase) 3 inhibitor TBHQ. Depleted acidic stores after nigericin or bafilomycin A1 were refilled by SERCA 3. Thrombin, but not ADP or AVP, reduces the rise in [Ca2+]c evoked by nigericin and bafilomycin A1. Our results indicate that the TBHQ-sensitive store in human platelets is an acidic organelle whose Ca2+ accumulation is regulated by both Ca2+- and vacuolar H+-ATPases.
大多数生理激动剂会增加胞质游离[Ca2+]c（胞质游离钙离子浓度）以调节多种细胞过程。不同刺激如何引发独特的时空Ca2+反应仍不清楚，且细胞内存在独立的Ca2+储存库可能具有重要的功能意义。Ca2+积累到细胞内区室主要取决于Ca2+ - 和H+ - ATP酶的活性。血小板存在两个独立的Ca2+储存库，它们对毒胡萝卜素和TBHQ [2,5 - 二 - （叔丁基）- 1,4 - 对苯二酚]的敏感性不同。虽然其中一个储存库长期以来被认为是致密管状系统，但TBHQ敏感储存库的性质仍不确定。用GPN（甘氨酰苯丙氨酸 - 2 - 萘酰胺）处理血小板会损害TBHQ诱导的Ca2+释放，并减少凝血酶诱导的Ca2+释放。相比之下，GPN不会改变ADP或AVP（精氨酸加压素）刺激的Ca2+动员。用质子载体尼日利亚菌素和液泡H+ - ATP酶抑制剂巴弗洛霉素A1处理以消除进入酸性细胞器的质子梯度，会诱导[Ca2+]c短暂升高，而先前用SERCA（肌浆网/内质网Ca2+ - ATP酶）3抑制剂TBHQ处理可消除这种升高。尼日利亚菌素或巴弗洛霉素A1处理后耗尽的酸性储存库可被SERCA 3重新填充。凝血酶而非ADP或AVP会减少尼日利亚菌素和巴弗洛霉素A1诱导的[Ca2+]c升高。我们的结果表明，人血小板中TBHQ敏感储存库是一种酸性细胞器，其Ca2+积累受Ca2+ - 和液泡H+ - ATP酶调节。
