Testican/SPOCK Family

Testicans, also called SPOCKs, make up a family of extracellular heparan/chondroitin sulfate proteoglycans. They are characterized structurally by an N-terminal testican-specific domain, a follistatin-like region, a calcium-binding domain, a thyroglobulin-like domain, and an acidic C-terminal domain with two putative glycosaminoglycan attachment sites. Testicans contain inhibitory regions in several domains targeted to different classes of protease, and in some cases may act as protease inhibitors. In addition to their presence in testis, testicans are enriched in brain and have been shown to regulate neuronal attachment and outgrowth.