title: Increased cell growth due to a new lipase-GEF (Phospholipase D2) fastly acting on Ras.
abstract: We report the novel finding that Phospholipase D2 (PLD2), through its PX and PH domains, binds specifically to Ras and catalyzes the GDP/GTP exchange (i.e., is a GEF), with potency comparable to Ras-GRF-1, a known Ras-GEF. Cells overexpressing PLD2-GEF inactive mutants (F129Y and R172C/L173A) fail to stimulate cell proliferation compared to the wild type-expressing cells. The GEF effect on Ras follows a faster kinetics than other GTPase substrates (such as Rac2 or Rac1) and is a better substrate, too. The GEF action is due to PLD2 (protein) itself, independent of the lipase product PA. PA can still have a fine-tuning regulatory effect on Ras-GTP depending upon its cellular concentration. Rapidly growing human breast cancer cells MDA-MB 231 (but not the slow growing MCF7 counterpart) have high levels of endogenous PLD2-GEF which correlates with high Ras activation. The PLD2-"GEF" activity is even higher than the classical "lipase" activity and is abrogated with GEF single point mutants, particularly F129Y, and concomitantly with a slow rate of cell growth. This can be crucial to cancer biology in that not only Ras mutations explain abnormal growth, but the existence of a new GEF for Ras: a GEF molecule that happens to be a phospholipase.
authors.affiliation: Wright State University School of Medicine, Department of Biochemistry and Molecular Biology, OH 45435, USA.
authors.forename: Karen M
authors.initials: KM
authors.lastname: Henkels
authors.forename: Madhu
authors.initials: M
authors.lastname: Mahankali
authors.forename: Julian
authors.initials: J
authors.lastname: Gomez-Cambronero
mesh_terms: D019943:Amino Acid Substitution; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D006153:Guanosine Diphosphate / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D061986:MCF-7 Cells; D010712:Phosphatidic Acids / Q000494:pharmacology; D010739:Phospholipase D / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D018631:ras Proteins / Q000378:metabolism*
chemical_list: D010712:Phosphatidic Acids; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate; C105606:phospholipase D2; D010739:Phospholipase D; D018631:ras Proteins