title: Conditional transformation mediated via a pertussis toxin-sensitive receptor signalling pathway.
abstract: To determine whether a cloned receptor coupled to pertussis toxin (PTx)-sensitive G-proteins can induce cell proliferation and oncogenic transformation, as observed for receptors that elicit PTx-insensitive enhancement of phosphatidyl inositol (PI)-specific phospholipase-C (PLC) activity, nontransformed murine BALB/c-3T3 cells were transfected with the rat serotonin-1A (5-HT1A) receptor. The 5-HT1A receptor is coupled to PTx-sensitive G-proteins to induce a cell-specific activation of PLC. While 1 microM 5-HT induced no change in PI turnover or cytosolic free calcium levels ([Ca2+]i) in receptor-negative nontransfected 3T3 cells, 5-HT induced a 2-fold increase in inositol trisphosphate accumulation and a 2.5-fold increase in [Ca2+]i in the 3T3-ZD8 clone, which expressed 0.6 +/- 0.2 pmol/mg protein of specific 5-HT1A binding sites. The stimulatory actions of 5-HT on PI turnover and [Ca2+]i in 3T3ZD8 cells displayed the pharmacology of the 5-HT1A receptor and were abolished by pretreatment with PTx. Thus, BALB/c-3T3 fibroblast cells express the PLC-linked pathway of the 5-HT1A receptor. Overnight treatment with 5-HT (1 microM) enhanced incorporation of [3H]thymidine into DNA extracted from serum-starved 3T3ZD-8 cells, an action that was also blocked by pretreatment with pertussis toxin. Long term (1-2 weeks) exposure to 5-HT in the medium led to phenotypic transformation of the cells, including the formation of foci with 1 microM 5-HT. These actions of 5-HT were not observed in untransformed 3T3 cells. We conclude that the PTx-sensitive PLC-linked pathway of the 5-HT1A receptor expressed in nontransformed BALB/c-3T3 cells, in concert with other serum-derived factors, predisposes the cells to enhanced proliferation and transformation.
authors.affiliation: Department of Pharmacology and Therapeutics, McGill University, Montreal, Quebec, Canada.
authors.forename: H
authors.initials: H
authors.lastname: Abdel-Baset
authors.forename: V
authors.initials: V
authors.lastname: Bozovic
authors.forename: M
authors.initials: M
authors.lastname: Szyf
authors.forename: P R
authors.initials: PR
authors.lastname: Albert
mesh_terms: D016475:3T3 Cells; D000818:Animals; D001483:Base Sequence; D002118:Calcium / Q000378:metabolism; D002455:Cell Division / Q000502:physiology; D002471:Cell Transformation, Neoplastic / Q000235:genetics; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D037342:Pertussis Toxin; D010716:Phosphatidylinositols / Q000502:physiology; D011985:Receptors, Serotonin / Q000502:physiology*; D012701:Serotonin / Q000502:physiology; D015398:Signal Transduction; D014162:Transfection; D010738:Type C Phospholipases / Q000502:physiology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
chemical_list: D010716:Phosphatidylinositols; D011985:Receptors, Serotonin; D010566:Virulence Factors, Bordetella; D012701:Serotonin; D037342:Pertussis Toxin; D010738:Type C Phospholipases; D002118:Calcium