title: The sterol-sensing domain of Patched protein seems to control Smoothened activity through Patched vesicular trafficking.
abstract: The Hedgehog (Hh) family of signaling molecules function as organizers in many morphogenetic processes. Hh signaling requires cholesterol in both signal-generating and -receiving cells, and it requires the tumor suppressor Patched (Ptc) in receiving cells in which it plays a negative role. Ptc both blocks the Hh pathway and limits the spread of Hh. Sequence analysis suggests that it has 12 transmembrane segments, 5 of which are homologous to a conserved region that has been identified in several proteins involved in cholesterol homeostasis and has been designated the sterol-sensing domain (SSD). In the present study, we show that a Ptc mutant with a single amino acid substitution in the SSD induces target gene activation in a ligand-independent manner. This mutant Ptc(SSD) protein shows dominant-negative activity in blocking Hh signaling by preventing the downregulation of Smoothened (Smo), a positive effector of the Hh pathway. Despite its dominant-negative activity, the mutant Ptc protein functioned like the wild-type protein in sequestering and internalizing Hh. In addition, we show that Ptc(SSD) preferentially accumulates in endosomes of the endocytic compartment. All these results suggest a role of the SSD of Ptc in mediating the vesicular trafficking of Ptc to regulate Smo activity.
authors.affiliation: Centro de Biología Molecular "Severo Ochoa," Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, Cantoblanco, E-28049, Madrid, Spain.
authors.forename: V
authors.initials: V
authors.lastname: Martín
authors.forename: G
authors.initials: G
authors.lastname: Carrillo
authors.forename: C
authors.initials: C
authors.lastname: Torroja
authors.forename: I
authors.initials: I
authors.lastname: Guerrero
mesh_terms: D000483:Alleles; D000818:Animals; D001665:Binding Sites; D001692:Biological Transport; D004330:Drosophila / Q000196:embryology / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D029721:Drosophila Proteins; D011992:Endosomes / Q000378:metabolism; D053823:Hedgehog Proteins; D019476:Insect Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D016296:Mutagenesis; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000378:metabolism*; D043562:Receptors, G-Protein-Coupled; D000072086:Smoothened Receptor; D013261:Sterols; D015854:Up-Regulation; D051155:Wnt1 Protein
chemical_list: D029721:Drosophila Proteins; D053823:Hedgehog Proteins; D019476:Insect Proteins; D008565:Membrane Proteins; D011518:Proto-Oncogene Proteins; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; D000072086:Smoothened Receptor; D013261:Sterols; D051155:Wnt1 Protein; C070844:ptc protein, Drosophila; C100664:smo protein, Drosophila; C074622:wg protein, Drosophila; C077245:hh protein, Drosophila