Ozawa T, Schulz I
Max-Planck-Institut für Biophysik, Frankfurt am Main, Fed. Rep. of Germany.
Biochem Biophys Res Commun. 1991 Oct 31;180(2):755-64. doi: 10.1016/s0006-291x(05)81130-1.
Evidence suggests that GTP but not GTP gamma S activates Ca2+ movement between myo-inositol 1,4,5-trisphosphate (IP3)-sensitive and -insensitive Ca2+ pools (1). Measuring 45Ca2+ uptake into pancreatic microsomal vesicles we have determined the sizes of three different Ca2+ pools which release Ca2+ in response 1) to IP3, 2) to caffeine, and 3) to both IP3 and caffeine ("common" Ca2+ pool). In the presence of GTP the size of the IP3-sensitive Ca2+ pool is decreased whereas the "common" Ca2+ pool is increased as compared to control Ca2+ pool sizes in the presence of GTP gamma S. This effect of GTP is inhibited by bafilomycin B1, a specific inhibitor of vacuolar type H+ ATPases (2). We conclude that GTP induced connection between IP3- and caffeine-sensitive Ca2+ pools is triggered by intravesicular acidification and involves function of small GTP-binding proteins, known to mediate interorganelle transfer.
有证据表明，鸟苷三磷酸（GTP）而非鸟苷三磷酸γ-硫酯（GTPγS）能激活肌醇1,4,5-三磷酸（IP3）敏感和不敏感的Ca2+池之间的Ca2+移动（1）。通过测量45Ca2+摄取到胰腺微粒体囊泡中的情况，我们确定了三种不同Ca2+池的大小，它们分别对以下刺激释放Ca2+：1）IP3，2）咖啡因，以及3）IP3和咖啡因两者（“共同”Ca2+池）。与存在GTPγS时的对照Ca2+池大小相比，在存在GTP的情况下，IP3敏感的Ca2+池大小减小，而“共同”Ca2+池大小增加。GTP的这种作用被巴弗洛霉素B1抑制，巴弗洛霉素B1是液泡型H+ATP酶的特异性抑制剂（2）。我们得出结论，GTP诱导的IP3敏感和咖啡因敏感的Ca2+池之间的连接是由囊泡内酸化触发的，并且涉及已知介导细胞器间转运的小GTP结合蛋白的功能。
