Precise regulation of porcupine activity is required for physiological Wnt signaling.
Gradients of diverse Wnt proteins regulate development, renewal, and differentiation. Porcupine (PORCN) is a membrane-bound O-acyltransferase that is required for post-translational modification of all Wnts to enable their transport, secretion, and activity. Mutations in PORCN are associated with focal dermal hypoplasia (FDH), whereas gene deletion causes embryonic lethality in mice. To study the protein in more detail, zinc finger nucleases were used to edit the PORCN genomic locus, establishing two HT1080 fibrosarcoma clones null for PORCN activity that facilitate the study of PORCN structure and function. We establish that PORCN is a key non-redundant node for the regulation of global Wnt signaling because PORCN null cells are completely incapable of autocrine Wnt signaling. The strength of Wnt signaling is exquisitely sensitive to PORCN expression, with a dynamic range of at least 3 orders of magnitude, suggesting that PORCN activity is a key modulator of all Wnt ligand activity. Consistent with this, we find that multiple FDH-associated mutants have only subtle alterations in enzyme activity yet are associated with a severe FDH phenotype. These studies support an essential regulatory role of PORCN in shaping Wnt signaling gradients.
Program in Cancer and Stem Cell Biology, Duke-National University of Singapore Graduate Medical School, 8 College Road, 169857 Singapore.
Kyle D
KD
Proffitt
David M
DM
Virshup
D000217:Acyltransferases; D000818:Animals; D045744:Cell Line, Tumor; D005489:Focal Dermal Hypoplasia / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D005786:Gene Expression Regulation / Q000502:physiology*; D056426:Genetic Loci / Q000502:physiology*; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D060449:Wnt Signaling Pathway / Q000502:physiology*; D029867:Xenopus Proteins / Q000235:genetics / Q000378:metabolism*; D014982:Xenopus laevis
D008565:Membrane Proteins; D029867:Xenopus Proteins; D000217:Acyltransferases; C491187:Porcn protein, mouse