title: Crosstalk between the phosphatidylinositol cycle and MAP kinase signaling pathways in Xenopus mesoderm induction.
abstract: Recent studies have established a role for the phosphoinositide (PI) cycle in the early patterning of Xenopus mesoderm. In explants, stimulation of this pathway in the absence of growth factors does not induce mesoderm, but when accompanied by growth factor treatment, simultaneous PI cycle stimulation results in profound morphological and molecular changes in the mesoderm induced by the growth factor. This suggests the possibility that the PI cycle exerts its influence via crosstalk, by modulating some primary mesoderm-inducing pathway. Given recent identification of mitogen-activated protein kinase (MAPK) as an intracellular mediator of some mesoderm-inducing signals, the present study explores MAPK as a potential site of PI cycle-mediated crosstalk. We report that MAPK activity, like PI cycle activity, increases in intact embryos during mesoderm induction. Phosphoinositide cycle stimulation during treatment of explants with basic fibroblast growth factor (bFGF) synergistically increases late-phase MAPK activity and potentiates bFGF-induced expression of Xbra, a MAPK-dependent mesodermal marker.
authors.affiliation: Department of Biology, The Johns Hopkins University, Baltimore, MD 21218, USA.
authors.forename: L
authors.initials: L
authors.lastname: Rose
authors.forename: W B
authors.initials: WB
authors.lastname: Busa
mesh_terms: D000818:Animals; D015415:Biomarkers; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000235:genetics; D004625:Embryo, Nonmammalian / Q000502:physiology; D004627:Embryonic Induction / Q000502:physiology*; D005326:Fetal Proteins; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology*; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D008648:Mesoderm / Q000187:drug effects / Q000502:physiology*; D008845:Microinjections; D010716:Phosphatidylinositols / Q000502:physiology*; D011985:Receptors, Serotonin / Q000187:drug effects / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000502:physiology; D012701:Serotonin / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D020825:T-Box Domain Proteins; D014157:Transcription Factors / Q000096:biosynthesis / Q000235:genetics; D014982:Xenopus laevis / Q000196:embryology*; D000098908:Brachyury Protein
chemical_list: D015415:Biomarkers; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D004268:DNA-Binding Proteins; D005326:Fetal Proteins; D016222:Fibroblast Growth Factor 2; D010716:Phosphatidylinositols; D011985:Receptors, Serotonin; D011993:Recombinant Fusion Proteins; D012701:Serotonin; D020825:T-Box Domain Proteins; D014157:Transcription Factors; D000098908:Brachyury Protein; C112812:serotonin 1C receptor