title: The Csk-binding protein PAG regulates PDGF-induced Src mitogenic signaling via GM1.
abstract: Spatial regulation is an important feature of signal specificity elicited by cytoplasmic tyrosine kinases of the Src family (SRC family protein tyrosine kinases [SFK]). Cholesterol-enriched membrane domains, such as caveolae, regulate association of SFK with the platelet-derived growth factor receptor (PDGFR), which is needed for kinase activation and mitogenic signaling. PAG, a ubiquitously expressed member of the transmembrane adaptor protein family, is known to negatively regulate SFK signaling though binding to Csk. We report that PAG modulates PDGFR levels in caveolae and SFK mitogenic signaling through a Csk-independent mechanism. Regulation of SFK mitogenic activity by PAG requires the first N-terminal 97 aa (PAG-N), which include the extracellular and transmembrane domains, palmitoylation sites, and a short cytoplasmic sequence. We also show that PAG-N increases ganglioside GM1 levels at the cell surface and, thus, displaces PDGFR from caveolae, a process that requires the ganglioside-specific sialidase Neu-3. In conclusion, PAG regulates PDGFR membrane partitioning and SFK mitogenic signaling by modulating GM1 levels within caveolae independently from Csk.
authors.affiliation: Centre de Recherche en Biochimie Macromoléculare, Centre National de la Recherche Scientifique UMR5237, Universities of Montpellier I and II, 34293 Montpellier, France.
authors.forename: Laurence
authors.initials: L
authors.lastname: Veracini
authors.forename: Valérie
authors.initials: V
authors.lastname: Simon
authors.forename: Véronique
authors.initials: V
authors.lastname: Richard
authors.forename: Burkhart
authors.initials: B
authors.lastname: Schraven
authors.forename: Vaclav
authors.initials: V
authors.lastname: Horejsi
authors.forename: Serge
authors.initials: S
authors.lastname: Roche
authors.forename: Christine
authors.initials: C
authors.lastname: Benistant
mesh_terms: D000818:Animals; D000081247:CSK Tyrosine-Protein Kinase; D021941:Caveolae / Q000187:drug effects / Q000648:ultrastructure; D004247:DNA / Q000096:biosynthesis; D005677:G(M1) Ganglioside / Q000378:metabolism*; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism*; D051379:Mice; D008934:Mitogens / Q000378:metabolism*; D008954:Models, Biological; D041681:NIH 3T3 Cells; D009439:Neuraminidase / Q000378:metabolism; D010750:Phosphoproteins / Q000737:chemistry / Q000378:metabolism*; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology*; D011485:Protein Binding / Q000187:drug effects; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000378:metabolism*; D017479:Receptors, Platelet-Derived Growth Factor / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D019061:src-Family Kinases
chemical_list: D036341:Intercellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D008934:Mitogens; C408344:Pag protein, mouse; D010750:Phosphoproteins; D010982:Platelet-Derived Growth Factor; D005677:G(M1) Ganglioside; D004247:DNA; D011505:Protein-Tyrosine Kinases; D017479:Receptors, Platelet-Derived Growth Factor; D000081247:CSK Tyrosine-Protein Kinase; D016392:Proto-Oncogene Proteins pp60(c-src); D019061:src-Family Kinases; C000631346:CSK protein, human; C511796:Neu3 protein, mouse; D009439:Neuraminidase