Tomura H, Okajima F, Akbar M, Abdul Majid M, Sho K, Kondo Y
Department of Physical Biochemistry, Gunma University, Maebashi, Japan.
Biochem Biophys Res Commun. 1994 Apr 29;200(2):986-92. doi: 10.1006/bbrc.1994.1547.
COS-7 cells were transfected with human somatostatin (SRIF) receptor type 1 and 2 (human SSTR1 and SSTR2, respectively) cDNAs. In human SSTR2-expressing cells, SRIF not only inhibited forskolin-induced cAMP accumulation but also stimulated phospholipase C and Ca2+ mobilization. While the inhibition of cAMP accumulation was completely reversed by pertussis toxin (PTX) treatment of the cells, SRIF-induced activation of phospholipase C and Ca2+ mobilization was partially but not completely inhibited by the toxin treatment. In human SSTR1-expressing cells, however, SRIF induced only slight inhibition of cAMP accumulation and stimulation of phospholipase C-Ca2+ system. We conclude that the transfected SSTR2 can couple to phospholipase C as well as adenylate cyclase in a stimulatory and inhibitory manner, respectively. Both PTX-sensitive and -insensitive GTP-binding proteins may be involved in the SSTR2 signal transduction mechanisms.
将人1型和2型生长抑素（SRIF）受体（分别为人类SSTR1和SSTR2）的cDNA转染至COS-7细胞。在表达人类SSTR2的细胞中，SRIF不仅抑制福斯高林诱导的cAMP积累，还刺激磷脂酶C和Ca2+动员。虽然细胞经百日咳毒素（PTX）处理后，cAMP积累的抑制作用完全逆转，但毒素处理仅部分而非完全抑制SRIF诱导的磷脂酶C激活和Ca2+动员。然而，在表达人类SSTR1的细胞中，SRIF仅轻微抑制cAMP积累并刺激磷脂酶C-Ca2+系统。我们得出结论，转染的SSTR2可以分别以刺激和抑制的方式与磷脂酶C以及腺苷酸环化酶偶联。PTX敏感和不敏感的GTP结合蛋白可能都参与了SSTR2信号转导机制。
