title: Distinct effects of the mesenchymal dysplasia gene variant of murine Patched-1 protein on canonical and non-canonical Hedgehog signaling pathways.
abstract: Hedgehog (Hh) signaling requires regulation of the receptor Patched-1 (Ptch1), which, in turn, regulates Smoothened activity (canonical Hh signaling) as well as other non-canonical signaling pathways. The mutant Ptch1 allele mesenchymal dysplasia (mes), which truncates the Ptch1 C terminus, produces a limited spectrum of developmental defects in mice as well as deregulation of canonical Hh signaling in some, but not all, affected tissues. Paradoxically, mes suppresses canonical Hh signaling and binds to Hh ligands with an affinity similar to wild-type mouse Ptch1 (mPtch1). We characterized the distinct activities of the mes variant of mPtch1 mediating Hh signaling through both canonical and non-canonical pathways. We demonstrated that mPtch1 bound c-src in an Hh-regulated manner. Stimulation with Sonic Hedgehog (Shh) of primary mammary mesenchymal cells from wild-type and mes animals activated Erk1/2. Although Shh activated c-src in wild-type cells, c-src was constitutively activated in mes mesenchymal cells. Transient assays showed that wild-type mPtch1, mes, or mPtch1 lacking the C terminus repressed Hh signaling in Ptch1-deficient mouse embryo fibroblasts and that repression was reversed by Shh, revealing that the C terminus was dispensable for mPtch1-dependent regulation of canonical Hh signaling. In contrast to these transient assays, constitutively high levels of mGli1 but not mPtch1 were present in primary mammary mesenchymal cells from mes mice, whereas the expression of mPtch1 was similarly induced in both mes and wild-type cells. These data define a novel signal transduction pathway involving c-src that is activated by the Hh ligands and reveals the requirement for the C terminus of Ptch in regulation of canonical and non-canonical Hh signaling pathways.
authors.affiliation: Department of Laboratory Medicine and Pathobiology, Faculty of Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada.
authors.forename: Malcolm C
authors.initials: MC
authors.lastname: Harvey
authors.affiliation: Department of Laboratory Medicine and Pathobiology, Faculty of Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada.
authors.forename: Andrew
authors.initials: A
authors.lastname: Fleet
authors.affiliation: Department of Laboratory Medicine and Pathobiology, Faculty of Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada.
authors.forename: Nadia
authors.initials: N
authors.lastname: Okolowsky
authors.affiliation: Department of Laboratory Medicine and Pathobiology, Faculty of Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada. Electronic address: paul.hamel@utoronto.ca.
authors.forename: Paul A
authors.initials: PA
authors.lastname: Hamel
mesh_terms: D000818:Animals; D000081247:CSK Tyrosine-Protein Kinase; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D017077:Culture Media, Conditioned; D015971:Gene Expression Regulation, Enzymologic; D057809:HEK293 Cells; D053823:Hedgehog Proteins / Q000378:metabolism*; D006801:Humans; D008024:Ligands; D051379:Mice; D008810:Mice, Inbred C57BL; D000072079:Patched Receptors; D000072081:Patched-1 Receptor; D010766:Phosphorylation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011956:Receptors, Cell Surface / Q000378:metabolism*; D015398:Signal Transduction; D019061:src-Family Kinases / Q000378:metabolism
chemical_list: D017077:Culture Media, Conditioned; D053823:Hedgehog Proteins; D008024:Ligands; C000606236:PTCH1 protein, human; D000072079:Patched Receptors; D000072081:Patched-1 Receptor; C000606240:Ptch1 protein, mouse; D011956:Receptors, Cell Surface; D000081247:CSK Tyrosine-Protein Kinase; D019061:src-Family Kinases; C000631346:CSK protein, human
keywords: Cell Signaling; Hedgehog; Patched-1; Receptor Modification; Receptor Regulation; SH3 Domains; Sonic Hedgehog; c-src