title: Anti-apoptotic signaling of pleiotrophin through its receptor, anaplastic lymphoma kinase.
abstract: The secreted growth factor pleiotrophin (PTN) can induce mitogenesis in cells that express the receptor for this growth factor, anaplastic lymphoma kinase (ALK). Here we examine the ability of PTN to produce anti-apoptotic signals. We demonstrate that PTN is a survival factor for SW-13 epithelial cells and show that ribozyme-mediated depletion of ALK from SW-13 cells abolishes this effect of PTN. Furthermore, in serum-starved NIH3T3 fibroblasts PTN prevents apoptosis (measured by annexin V staining) with an EC(50) of 0.2 ng/ml and induces cell growth at higher concentrations of PTN. A polyclonal antibody against the PTN ligand-binding domain of the ALK receptor (alpha-LBD) was a partial agonist for ALK in NIH3T3 cells. This alpha-LBD antibody showed high agonist activity for anti-apoptosis (56 +/- 9% relative to PTN), low agonist activity for cell growth (21 +/- 1% relative to PTN), and was an antagonist of PTN-induced cell growth (61 +/- 2% inhibition). Both MAP kinase and phosphatidylinositol (PI) 3-kinase cascades in NIH3T3 cells were activated by PTN, and this effect persisted for up to 3 h. Surprisingly, the anti-apoptotic effect of PTN was completely blocked by the MAP kinase inhibitor UO126, but was not affected by the PI 3-kinase inhibitor LY294002. In contrast, PTN-dependent cell growth required both MAPK and PI 3-kinase activity. We conclude that anti-apoptotic signaling of PTN through ALK in NIH3T3 fibroblasts is via the MAP kinase pathway.
authors.affiliation: Department of Oncology, Lombardi Cancer Center, Georgetown University Medical School, Washington, D. C. 20007, USA.
authors.forename: Emma T
authors.initials: ET
authors.lastname: Bowden
authors.forename: Gerald E
authors.initials: GE
authors.lastname: Stoica
authors.forename: Anton
authors.initials: A
authors.lastname: Wellstein
mesh_terms: D016475:3T3 Cells; D000077548:Anaplastic Lymphoma Kinase; D000818:Animals; D017209:Apoptosis; D002352:Carrier Proteins / Q000378:metabolism*; D002469:Cell Separation; D002470:Cell Survival; D016895:Culture Media, Serum-Free / Q000494:pharmacology; D016207:Cytokines / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D005434:Flow Cytometry; D016650:Fluorescein-5-isothiocyanate / Q000494:pharmacology; D006801:Humans; D015151:Immunoblotting; D008024:Ligands; D020935:MAP Kinase Signaling System; D051379:Mice; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D011485:Protein Binding; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D016337:RNA, Catalytic / Q000378:metabolism; D020794:Receptor Protein-Tyrosine Kinases; D015398:Signal Transduction; D013997:Time Factors; D014407:Tumor Cells, Cultured
chemical_list: D002352:Carrier Proteins; D016895:Culture Media, Serum-Free; D016207:Cytokines; D008024:Ligands; D016337:RNA, Catalytic; C066845:pleiotrophin; D019869:Phosphatidylinositol 3-Kinases; C000626173:ALK protein, human; C000626174:Alk protein, mouse; D000077548:Anaplastic Lymphoma Kinase; D011505:Protein-Tyrosine Kinases; D020794:Receptor Protein-Tyrosine Kinases; D016650:Fluorescein-5-isothiocyanate