title: Functional inhibition of PI3K by the betaGBP molecule suppresses Ras-MAPK signalling to block cell proliferation.
abstract: The mechanisms of signal transduction from cell surface receptors to the interior of the cell are fundamental to the understanding of the role that positive and negative growth factors play in cell physiology and in human diseases. Here, we show that a functional link between phosphatidylinositol-3-OH kinase (PI3K) and Ras is suppressed by the beta-galactoside binding protein (betaGBP) molecule, a cytokine and a negative cell-cycle regulator. Ras-mitogen-activated protein kinase (MAPK) signalling is blocked by betaGBP owing to its ability to inhibit the p110 catalytic subunit of PI3K, whose basal activity is required for Ras activation. Functional inhibition of p110 by betaGBP results in downregulation of PI3K activity, suppression of Ras-GTP loading, consequent loss of MAPK activation and block of cell proliferation. This study sheds light on the molecular mechanisms whereby betaGBP can control cell proliferation and, by extension, may potentially control tumorigenesis by controlling PI3K.
authors.affiliation: Cell Signalling and Growth Laboratory, Pharmaceutical Science Research Division, King's College London, London, UK.
authors.forename: V
authors.initials: V
authors.lastname: Wells
authors.forename: J
authors.initials: J
authors.lastname: Downward
authors.forename: L
authors.initials: L
authors.lastname: Mallucci
mesh_terms: D000818:Animals; D049109:Cell Proliferation / Q000187:drug effects; D002471:Cell Transformation, Neoplastic / Q000235:genetics / Q000378:metabolism*; D037483:Galectin 1 / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011994:Recombinant Proteins / Q000235:genetics / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects; D018631:ras Proteins / Q000378:metabolism*
chemical_list: D037483:Galectin 1; D020928:Mitogen-Activated Protein Kinases; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011994:Recombinant Proteins; D018631:ras Proteins; C445499:LGALS1 protein, human