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Defining roles of the sterol recognition region in Hedgehog cholesterolyation
Author(s) -
Purohit Rahul,
Vielmas Erika,
Peng Daniel S.,
Ondrus Alison
Publication year - 2020
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.2020.34.s1.09381
Subject(s) - morphogen , smoothened , hedgehog , patched , hedgehog signaling pathway , chemistry , microbiology and biotechnology , sonic hedgehog , biology , biochemistry , signal transduction , gene
The Hedgehog (Hh) signaling pathway plays an essential role during embryogenesis and when dysregulated, can lead to human cancer (basal cell carcinomas) and the most lethal form of juvenile medulloblastoma. Binding of the Hh ligand to its receptor Patched (Ptch) relieves inhibition of the GPCR protein Smoothened (Smo) leading to activation of the Gli transcription factors and changes in target gene expression. The Hh ligand is decorated with two covalent modifications, N‐terminal palmitoylation and C‐terminal cholesterolyation. Hh proteins are synthesized as approximately 45 kDa full‐length species, whereupon a unique process yields the mature morphogen: an autocatalytic cleavage that splits the protein in two and attaches cholesterol to the newly formed C‐terminus. Of the two approximately equal molecular weight cleavage products, the dually lipidated N‐terminal fragment (Hh‐N/“Hog” domain) constitutes the classical Hh morphogen, whereas the C‐terminus (Hh‐C/“Hint”) is responsible for the cleavage reaction. In order to elucidate the chemical mechanism of cholesterolyation, we have determined the roles of the previously uncharacterized sterol recognition region (SRR) in Hh proteins. Using bioinformatics, alanine scanning, and biochemical assays we have identified key motifs and specified residues of the SRR that are required for biochemical processing of Hh. These results provide a first in detail insights into the role of this unique small region of the Hh protein that is capable of cellular targeting and engaging cholesterol to generate an active Hh ligand. Support or Funding Information This work was supported by the Margaret E. Early Medical Research Trust.