Jackson T R, Stephens L R, Hawkins P T
Department of Biochemistry, Institute of Animal Physiology and Genetics Research, Babraham, Cambridge, United Kingdom.
J Biol Chem. 1992 Aug 15;267(23):16627-36.
We have investigated synthesis of 3-phosphorylated inositol lipids in growth factor-stimulated Swiss 3T3 cells. Those growth factors tested which act via tyrosine kinase-containing receptors (platelet-derived growth factor (PDGF), insulin growth factor I (IGF-I), epidermal growth factor (EGF), and basic fibroblast growth factor (bFGF)) caused the rapid synthesis of [32P]PtdIns(3,4)P2 and [32P]PtdIns(3,4,5)P3 (PtdIns is phosphatidylinositol) in [32P]P(i)-prelabeled cells and the appearance of an inositol lipid 3-OH kinase in antiphosphotyrosine immunoprecipates. In contrast, those growth factors tested which act via G-protein-coupled receptors (bombesin, vasopressin, prostaglandin E1) were unable to stimulate either of the above responses. Furthermore, while PDGF was able to increase the formation of PtdIns(3,4)P2 and PtdIns(3,4,5)P3 in streptolysin-permeabilized cells, guanosine 5'-3-(thio)triphosphate and guanyl-5'-yl imidodiphosphate were not. These results suggest that Swiss 3T3 cells possess the machinery for tyrosine kinase but not G-protein-mediated activation of PtdIns(4,5)P2 3-OH kinase; a situation which is the inverse to that recently described for human neutrophils. The tyrosine kinase-containing receptors differed markedly in their relative abilities to elevate the levels of [32P] PtdIns(3,4,5)P3 (ranked in the order PDGF greater than or equal to IGF-I greater than EGF greater than bFGF), [32P]Ptd-OH (PDGF greater than EGF greater than bFGF; undetectable for IGF-I), and [32P]PtdIns4P (EGF greater than bFGF greater than PDGF; undetectable for IGF-I) in [32P]P(i)-prelabeled cells. These differences are epitomized by IGF-I, which was the joint most powerful stimulus for [32P] PtdIns(3,4,5)P3 formation, but was unable to stimulate a measurable accumulation of [32P]Ptd-OH (and hence, by deduction, was unable to stimulate phospholipase C). These results indicate that there is a differential ability among the tyrosine kinase-containing receptors present in a single cell to recruit phospholipase C and PtdIns(4,5)P2 3-OH kinase into their signalling complexes and further emphasizes the notion that the rapid synthesis of PtdIns(3,4,5)P3 may be a signalling event.
我们研究了生长因子刺激的瑞士3T3细胞中3 - 磷酸化肌醇脂质的合成。所测试的那些通过含酪氨酸激酶的受体起作用的生长因子（血小板衍生生长因子（PDGF）、胰岛素生长因子I（IGF - I）、表皮生长因子（EGF）和碱性成纤维细胞生长因子（bFGF）），在[³²P]P(i)预标记的细胞中导致了[³²P]PtdIns(3,4)P2和[³²P]PtdIns(3,4,5)P3（PtdIns是磷脂酰肌醇）的快速合成，并且在抗磷酸酪氨酸免疫沉淀物中出现了一种肌醇脂质3 - OH激酶。相比之下，所测试的那些通过G蛋白偶联受体起作用的生长因子（蛙皮素、血管加压素、前列腺素E1）无法刺激上述任何一种反应。此外，虽然PDGF能够增加链球菌溶血素通透细胞中PtdIns(3,4)P2和PtdIns(3,4,5)P3的形成，但鸟苷5'-3-(硫代)三磷酸和鸟苷5'-亚基亚氨基二磷酸却不能。这些结果表明瑞士3T3细胞具有酪氨酸激酶介导而非G蛋白介导的PtdIns(4,5)P2 3 - OH激酶激活机制；这种情况与最近描述的人类中性粒细胞的情况相反。含酪氨酸激酶的受体在升高[³²P]PtdIns(3,4,5)P3水平的相对能力上有显著差异（按顺序排列为PDGF≥IGF - I＞EGF＞bFGF），在[³²P]P(i)预标记的细胞中，[³²P]Ptd - OH（PDGF＞EGF＞bFGF；IGF - I未检测到）和[³²P]PtdIns4P（EGF＞bFGF＞PDGF；IGF - I未检测到）也是如此。这些差异以IGF - I为典型，它是[³²P]PtdIns(3,4,5)P3形成的最强大联合刺激物之一，但却无法刺激[³²P]Ptd - OH的可测量积累（因此，通过推断，无法刺激磷脂酶C）。这些结果表明，单个细胞中存在的含酪氨酸激酶的受体在将磷脂酶C和PtdIns(4,5)P2 3 - OH激酶募集到其信号复合物中的能力上存在差异，并进一步强调了PtdIns(3,4,5)P3的快速合成可能是一个信号事件的观点。
