Structural insights into hedgehog ligand sequestration by the human hedgehog-interacting protein HHIP

Nat Struct Mol Biol. 2009 Jul;16(7):698-703. doi: 10.1038/nsmb.1607. Epub 2009 Jun 28.

Abstract

Hedgehog (Hh) morphogens have fundamental roles in development, whereas dysregulation of Hh signaling leads to disease. Multiple cell-surface receptors are responsible for transducing and/or regulating Hh signals. Among these, the Hedgehog-interacting protein (Hhip) is a highly conserved, vertebrate-specific inhibitor of Hh signaling. We have solved a series of crystal structures for the human HHIP ectodomain and Desert hedgehog (DHH) in isolation, as well as HHIP in complex with DHH (HHIP-DHH) and Sonic hedgehog (Shh) (HHIP-Shh), with and without Ca2+. The interaction determinants, confirmed by biophysical studies and mutagenesis, reveal previously uncharacterized and distinct functions for the Hh Zn2+ and Ca2+ binding sites--functions that may be common to all vertebrate Hh proteins. Zn2+ makes a key contribution to the Hh-HHIP interface, whereas Ca2+ is likely to prevent electrostatic repulsion between the two proteins, suggesting an important modulatory role. This interplay of several metal binding sites suggests a tuneable mechanism for regulation of Hh signaling.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Binding Sites
  • Calcium / metabolism
  • Carrier Proteins / chemistry*
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism*
  • Hedgehog Proteins / chemistry*
  • Hedgehog Proteins / genetics
  • Hedgehog Proteins / metabolism
  • Humans
  • Ligands
  • Membrane Glycoproteins / chemistry*
  • Membrane Glycoproteins / genetics
  • Membrane Glycoproteins / metabolism*
  • Models, Molecular
  • Molecular Sequence Data
  • Multiprotein Complexes / metabolism
  • Protein Structure, Secondary*
  • Protein Structure, Tertiary*
  • Zinc / metabolism

Substances

  • Carrier Proteins
  • HHIP protein, human
  • Hedgehog Proteins
  • Ligands
  • Membrane Glycoproteins
  • Multiprotein Complexes
  • SHH protein, human
  • Zinc
  • Calcium

Associated data

  • PDB/2WFQ
  • PDB/2WFR
  • PDB/2WFT
  • PDB/2WFX
  • PDB/2WG3
  • PDB/2WG4