ABSTRACT
Wnt signaling is essential for normal development and is a therapeutic target in cancer. The enzyme PORCN, or porcupine, is a membrane-bound O-acyltransferase (MBOAT) that is required for the post-translational modification of all Wnts, adding an essential mono-unsaturated palmitoleic acid to a serine on the tip of Wnt hairpin 2. Inherited mutations in PORCN cause focal dermal hypoplasia, and therapeutic inhibition of PORCN slows the growth of Wnt-dependent cancers. Here, based on homology to mammalian MBOAT proteins we develop and validate a molecular structural model of PORCN. The model accommodates palmitoleoyl-CoA and Wnt hairpin 2 in two tunnels in the conserved catalytic core, shedding light on the catalytic mechanism. The model predicts how previously uncharacterized human variants of uncertain significance can alter PORCN function. Drugs including ETC-159, IWP-L6 and LGK-974 dock in the PORCN catalytic site, providing insights into PORCN pharmacologic inhibition. This structural model provides mechanistic insights into PORCN substrate recognition and catalysis as well as the inhibition of its enzymatic activity and can facilitate the development of improved inhibitors and the understanding of disease relevant PORCN mutants.
Competing Interest Statement
WX and TK are employees of the Experimental Drug Development Centre. This institute has a commercial interest in the development of ETC-159. DMV also has financial interest in ETC-159. Other authors declare no competing interests.
Footnotes
Funding Information: The National Research Foundation, administered by the Singapore Ministry of Health’s National Medical Research Council under Singapore Translational Research (STaR) Award MOH-000155 to D.M.V.
Competing Interests: WX and TK are employees of the Experimental Drug Development Centre. This institute has a commercial interest in the development of ETC-159. DMV also has financial interest in ETC-159. Other authors declare no competing interests.
corrected typos in section on competing interests and supplemental figure legends.