Cysteine-rich domain of the secreted frizzled-related protein 2 (SFRP2), a regulator of Wnt activity.
The cysteine-rich-domain (CRD) is an essential part of the secreted frizzled related protein 2 (SFRP2), which regulates the activity of Wnt proteins, key players in a number of fundamental cellular processes such as embryogenesis and postnatal development. SFRPs antagonize the activation of Wnt signaling by binding to CRD domains of frizzled (Fz) proteins, thereby preventing Wnt proteins from binding to these receptors. SFRPs and Fz proteins both contain CRD domains, but SFRPs lack the seven-pass transmembrane domain which is an integral part of Fzs. As a Wnt antagonist, SFRP2 regulates Nkx2.2 expression in the ventral spinal cord and anteroposterior axis elongation. SFRP2 also has a Wnt-independent function as an enhancer of procollagen cleavage by the TLD proteinases. SFRP2 binds both procollagen and TLD, thus facilitating the enzymatic reaction by bringing together the proteinase and its substrate.