The function of FZD1 (frizzled class receptor 1, ENSG00000157240) is as follows. Receptor for Wnt proteins (PubMed:10557084). Activated by WNT3A, WNT3, WNT1 and to a lesser extent WNT2, but apparently not by WNT4, WNT5A, WNT5B, WNT6, WNT7A or WNT7B (PubMed:10557084). Contradictory results showing activation by WNT7B have been described for mouse (By similarity). Functions in the canonical Wnt/beta-catenin signaling pathway (PubMed:10557084). The canonical Wnt/beta-catenin signaling pathway leads to the activation of disheveled proteins, inhibition of GSK-3 kinase, nuclear accumulation of beta-catenin and activation of Wnt target genes (PubMed:10557084). A second signaling pathway involving PKC and calcium fluxes has been seen for some family members, but it is not yet clear if it represents a distinct pathway or if it can be integrated in the canonical pathway, as PKC seems to be required for Wnt-mediated inactivation of GSK-3 kinase. Both pathways seem to involve interactions with G proteins. May be involved in transduction and intercellular transmission of polarity information during tissue morphogenesis and/or in differentiated tissues (Probable). {ECO:0000250|UniProtKB:O70421, ECO:0000269|PubMed:10557084, ECO:0000305}. (Microbial infection) Acts as a receptor for C.difficile toxin TcdB in the colonic epithelium. .