Wehmeyer A, Schulz R
Institute of Pharmacology, Toxicology and Pharmacy, University of Munich, München, Germany.
Life Sci. 1998;62(9):PL127-34. doi: 10.1016/s0024-3205(97)01190-9.
Phosducin (Phd), a cytosolic protein, has been proposed to compete with certain receptor kinases for Gbetagamma of heterotrimeric G proteins, and may inhibit GTPase activity of G alpha s. These suggestions together with the enhancing effect of Phd on odorant-induced cAMP accumulation let us assume a stimulatory action of the protein on intracellular signaling. Therefore, this investigation was designed to examine the excitatory effect of PGE1 on signal transmission in neuroblastoma x glioma hybrid cells (NG 108-15) overexpressing Phd. The neuronal cells stably expressing Phd were found to display a 3 to 4-fold increased sensitivity to PGE1 as compared to wild type cells, using cAMP accumulation as measure. Examination of membranes prepared from Phd-overexpressing cells revealed an elevated GTPase activity as indicated by the formation of 32Pi upon PGE1 challenge. This activity was inhibited by exogenous Phd. In addition, receptor independent stimulation of adenylate cyclase by forskolin reveals an increased formation of cAMP in Phd expressing cells, which is accompanied by an increased binding of [3H]forskolin. The findings let us propose that Phd elevates intracellular levels of functional G alpha s which accounts for the increased response to PGE1.
磷光视蛋白（Phd）是一种胞质蛋白，有人提出它能与某些受体激酶竞争异源三聚体G蛋白的Gβγ，并可能抑制Gαs的GTP酶活性。这些观点以及Phd对气味诱导的cAMP积累的增强作用，使我们推测该蛋白对细胞内信号传导具有刺激作用。因此，本研究旨在检测前列腺素E1（PGE1）对过表达Phd的神经母细胞瘤×胶质瘤杂交细胞（NG 108-15）信号传导的兴奋作用。以cAMP积累作为衡量指标，发现稳定表达Phd的神经元细胞对PGE1的敏感性比野生型细胞提高了3至4倍。对过表达Phd的细胞制备的膜进行检测发现，PGE1刺激后32Pi的形成表明GTP酶活性升高。这种活性受到外源性Phd的抑制。此外，福斯可林对腺苷酸环化酶的非受体依赖性刺激显示，在表达Phd的细胞中cAMP的形成增加，同时伴有[3H]福斯可林结合增加。这些发现使我们提出，Phd提高了功能性Gαs的细胞内水平，这解释了对PGE1反应的增加。
