Structures of human Patched and its complex with native palmitoylated sonic hedgehog

Nature. 2018 Aug;560(7716):128-132. doi: 10.1038/s41586-018-0308-7. Epub 2018 Jul 11.

Abstract

Hedgehog (HH) signalling governs embryogenesis and adult tissue homeostasis in mammals and other multicellular organisms1-3. Whereas deficient HH signalling leads to birth defects, unrestrained HH signalling is implicated in human cancers2,4-6. N-terminally palmitoylated HH releases the repression of Patched to the oncoprotein smoothened (SMO); however, the mechanism by which HH recognizes Patched is unclear. Here we report cryo-electron microscopy structures of human patched 1 (PTCH1) alone and in complex with the N-terminal domain of 'native' sonic hedgehog (native SHH-N has both a C-terminal cholesterol and an N-terminal fatty-acid modification), at resolutions of 3.5 Å and 3.8 Å, respectively. The structure of PTCH1 has internal two-fold pseudosymmetry in the transmembrane core, which features a sterol-sensing domain and two homologous extracellular domains, resembling the architecture of Niemann-Pick C1 (NPC1) protein7. The palmitoylated N terminus of SHH-N inserts into a cavity between the extracellular domains of PTCH1 and dominates the PTCH1-SHH-N interface, which is distinct from that reported for SHH-N co-receptors8. Our biochemical assays show that SHH-N may use another interface, one that is required for its co-receptor binding, to recruit PTCH1 in the absence of a covalently attached palmitate. Our work provides atomic insights into the recognition of the N-terminal domain of HH (HH-N) by PTCH1, offers a structural basis for cooperative binding of HH-N to various receptors and serves as a molecular framework for HH signalling and its malfunction in disease.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Binding Sites
  • Cholesterol / metabolism
  • Cryoelectron Microscopy*
  • Fatty Acids / metabolism
  • Hedgehog Proteins / chemistry*
  • Hedgehog Proteins / metabolism
  • Hedgehog Proteins / ultrastructure*
  • Humans
  • Ligands
  • Lipoylation*
  • Models, Molecular
  • Palmitic Acid / metabolism*
  • Patched-1 Receptor / chemistry*
  • Patched-1 Receptor / ultrastructure*
  • Protein Domains

Substances

  • Fatty Acids
  • Hedgehog Proteins
  • Ligands
  • PTCH protein, human
  • Patched-1 Receptor
  • SHH protein, human
  • Palmitic Acid
  • Cholesterol