Activated type I phosphatidylinositol kinase is associated with the epidermal growth factor (EGF) receptor following EGF stimulation.

Abstract

We have shown that a type I phosphatidylinositol (PI) kinase activity is associated with the epidermal growth factor (EGF) receptor in a mouse fibroblast cell line expressing human EGF receptors (NRHER5) and that this activity increases dramatically upon treatment of cells with physiologically relevant concentrations of EGF. EGF stimulated a time-dependent increase in EGF receptor-associated PI kinase activity measured in EGF receptor immunoprecipitates.Activation was detected 15 min after the addition of EGF, and it peaked between 1 and 2 hr. Activation of PI kinase was detected with EGF concentrations as low as 10 pM and maximal stimulation occurred at -1 nM. Analysis of deacylated PI phosphate products, and inhibition of the PI kinase activity by nonionic detergent, indicated that the PI kinase described here was type I or PI 3' kinase. These results demonstrate the regulation of a type I PI kinase by EGF and suggest a potential role in the EGF receptor signal transduction pathway.In recernt years, several steps involved in signal transduction pathways mediated by epidermal growth factor (EGF) have been elucidated. Early responses (<1 hr) include the clustering and internalization of EGF receptors (1, 2), activation of the intrinsic tyrosine kinase activity of the EGF receptor (3) resulting in autophosphorylation (4) and phosphorylation of exogenous substrates (for review, see ref. 5) on tyrosine residues, generation of ion fluxes (6), stimulation of phosphatidylinositol (PI) turnover (7), and induction of the protooncogenes c-myc and c-fos (8). Late responses (>1 hr) include the stimulation of DNA synthesis and cell proliferation (9,10). Although many of the effects of receptor activation have been carefully documented, it appears that additional important information is required to establish which of these documented responses are critical for late events such as cell division. In addition, there most certainly are important cellular events that remain to be uncovered.One family of growth factor-activated signals that has drawn a large amount of interest recently includes those derived from the PI pathway. These include the second messengers inositol 1,4,5-trisphosphate, which has been implicated in the mobilization of intracellular calcium (11,12), and diacylglycerol, which activates the calcium-and phospholipid-dependent kinase protein kinase C (13,14). In addition, a number of other second messengers, including prostaglandins, PI polyphosphates, and inositol polyphosphates, are generated, which may have important roles in cell growth (for review, see ref. 15).EGF has been shown to stimulate PI turnover in a variety of cell types (7, 16-18), presumably through phosphorylation and activation of phospholipase C (19)(20)(21)(22). In addition, partially purified EGF receptor preparations have been found to contain an associated PI kinase activity (23) and EGF treatment of some cell types (e.g., the human epidermoid carcinoma cell line A431) results in PI kinase activation (24). In this report, we demo...

Specific association of phosphatidylinositol 3‐kinase with the protooncogene product Cbl in Fcγ receptor signaling

“…Abbreviations: FcyR, Fc receptor for IgG; Pl, phosphatidylinositol; p85, 85-kDa subunit of Pl 3-kinase; PI-3P, PI 3.phosphate stimulating factor-I [21][22][23][24][25][26]. PI 3-kinase has also been activated after stimulation of a variety of the receptors lacking tyrosine kinase domains.…”

Apc Deficiency Is Associated with Increased Egfr Activity in the Intestinal Enterocytes and Adenomas of C57BL/6J-Min/+ Mice

“…6D, top). Gab1 is tyrosine-phosphorylated by activated RTKs (63,64,66), as well as c-Src (65). Precipitation of Gab1 and immunoblot analysis using anti-p-Y antibody showed that expression of tyrosine-phosphorylated Gab1 was greater in adenomas (Fig.…”

“…6B). Growth factor-dependent EGFR activation induces PI3K activity (66). Precipitating Egfr in the samples and immunoblotting for p85␣ (Fig.…”

The SH3 domain of p56lck is involved in binding to phosphatidylinositol 3'-kinase from T lymphocytes.

“…Furthermore, a strong correlation between the mitogenic response and associated PI3K activity in receptor-type tyrosine kinases has been reported (9,12,13,46). Similarly, PI3K association with transforming or activated forms of pp60vsrC or pp60csrC and with polyomavirus middle-T antigen-c-Src complexes has suggested a possible correlation with cell transformation ability (4,7,10,24,56). The correlation between PI3K and receptor tyrosine kinases, as well as the link between P13K and the transformation potential of pp6Osrc, is suggestive of a novel signal transduction pathway involving PI 3-phosphate (PI-3-P).…”

“…More recently, a novel PI kinase that phosphorylates inositol at the D-3 position has been identified (57). This enzyme, known as PI 3-kinase (PI3K), has subsequently been found to associate with several tyrosine kinase oncogenes and proto-oncogenes (2,4,7,9,14). Furthermore, a strong correlation between the mitogenic response and associated PI3K activity in receptor-type tyrosine kinases has been reported (9,12,13,46).…”