Phosphatidylinositol 3-kinase activity is required at a postendocytic step in platelet-derived growth factor receptor trafficking
Program in Molecular Medicine
1-Phosphatidylinositol 3-Kinase; Androstadienes; Binding Sites; Biological Transport; Cell Line; Down-Regulation; *Endocytosis; Humans; Hydrolysis; Phosphorylation; Phosphotransferases (Alcohol Group Acceptor); inhibitors; Receptors, Platelet-Derived Growth Factor; Tyrosine
Life Sciences | Medicine and Health Sciences
We have previously reported that platelet-derived growth factor (PDGF) receptor mutants that lack high affinity binding sites for phosphatidylinositol 3-kinase (PI 3-kinase) fail to concentrate in juxtanuclear vesicular structures after activation with PDGF. We have now identified the point in the endocytic pathway at which PI 3-kinase binding sites are required. Receptor internalization from the plasma membrane, measured as the acquisition of acid resistance of prebound 125I-PDGF, was only slightly decreased in cells expressing a PDGF receptor mutant (F5) lacking PI 3-kinase, GTPase-activating protein (GAP), phospholipase C gamma, and Syp binding sites but not expressing mutants where any of these individual sites were restored nor expressing a mutant lacking exclusively PI 3-kinase binding sites. In contrast, the extent of down-regulation of PDGF binding sites from the cell surface after prolonged incubation with PDGF as well as the degradation of [35S]methionine-labeled receptor were markedly reduced in cells expressing the F5 mutant, mutants restored in GAP, phospholipase C gamma, or Syp binding sites or expressing the mutant exclusively lacking PI 3-kinase binding sites but not in cells expressing the mutant where PI 3-kinase binding sites were restored. Inhibition of PI 3-kinase activity with wortmannin caused a dramatic decrease in the rates of down-regulation and degradation of wild-type receptors. These results suggest that PI 3-kinase binding sites are not required for internalization of PDGF receptor but are required to divert the PDGF receptor to a degradative pathway. Furthermore, the requirement for PI 3-kinase binding sites on the receptor appears to be due to a requirement for PI 3-kinase catalytic activity.
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Citation: J Biol Chem. 1995 Jun 2;270(22):13225-30.
The Journal of biological chemistry
Joly, Marguerite; Kazlauskas, Andrius; and Corvera, Silvia, "Phosphatidylinositol 3-kinase activity is required at a postendocytic step in platelet-derived growth factor receptor trafficking" (1995). Open Access Articles. 810.