The function of NKD2 (NKD inhibitor of Wnt signaling pathway 2, Ensembl gene identifier ENSG00000145506) is as follows. Cell autonomous antagonist of the canonical Wnt signaling pathway. May activate a second Wnt signaling pathway that controls planar cell polarity (By similarity). Required for processing of TGFA and for targeting of TGFA to the basolateral membrane of polarized epithelial cells. {ECO:0000250, ECO:0000269|PubMed:15064403, ECO:0000269|PubMed:17553928}.