Ku C Y, Qian A, Wen Y, Anwer K, Sanborn B M
Department of Biochemistry and Molecular Biology, University of Texas Houston Medical School 77030.
Endocrinology. 1995 Apr;136(4):1509-15. doi: 10.1210/endo.136.4.7895660.
Oxytocin stimulates phosphoinositide turnover in myometrium. To elucidate whether the coupling mechanism involves the interaction of oxytocin receptor with GTP-binding proteins, we examined oxytocin stimulation of guanosine triphosphatase (GTPase) activity and phospholipase-C activity in rat and human myometrial membranes. Oxytocin consistently stimulated both GTPase and phospholipase-C activities, and both stimulations were attenuated by an antibody directed against the carboxyl-terminals of the GTP-binding proteins, G alpha q and G alpha 11. Neutralization of the antibody by preincubation with antigenic peptide reversed this inhibition. [Thr4,Gly7]oxytocin, a specific oxytocin receptor agonist, stimulated both GTPase and phospholipase-C activities, and the stimulations were also inhibited by anti-G alpha q/11 IgG. Immunoreactive GTP-binding proteins, G alpha q and G alpha 11, and phospholipase-C beta 3 isoforms were present in myometrial membranes. These results indicate that stimulation of phospholipase-C activity by oxytocin in myometrium is mediated via G alpha q, G alpha 11, or a closely related GTP-binding protein, probably coupling to phospholipase-C beta.
催产素可刺激子宫肌层中的磷酸肌醇转换。为了阐明这种偶联机制是否涉及催产素受体与GTP结合蛋白的相互作用，我们检测了催产素对大鼠和人子宫肌层膜中鸟苷三磷酸酶（GTPase）活性和磷脂酶C活性的刺激作用。催产素始终能刺激GTPase和磷脂酶C的活性，并且这两种刺激作用都被一种针对GTP结合蛋白Gαq和Gα11羧基末端的抗体所减弱。通过与抗原肽预孵育使抗体中和可逆转这种抑制作用。[苏氨酸4，甘氨酸7]催产素，一种特异性的催产素受体激动剂，能刺激GTPase和磷脂酶C的活性，并且这些刺激作用也被抗Gαq/11 IgG所抑制。免疫反应性GTP结合蛋白Gαq和Gα11以及磷脂酶Cβ3亚型存在于子宫肌层膜中。这些结果表明，催产素在子宫肌层中对磷脂酶C活性的刺激是通过Gαq、Gα11或一种密切相关的GTP结合蛋白介导的，可能与磷脂酶Cβ偶联。
