Background information
The Testican family, also designated the BM-40/SPARC/osteonectin family, is composed of highly conserved, extracellular, calcium-binding, sulfate proteoglycans. Expression of Testicans is detected in a variety of tissues, but is most abundant in brain. Family members include Testican-1, Testican-2, Testican-3 and an amino-terminal splice variant of Testican-3, designated N-Tes. Most Testicans inhibit MT-MMPs, thereby inhibiting the activity of pro-MMP-2. Testican-2 is expressed in the central nervous system (CNS), with widespread expression in the olfactory bulb, cerebral cortex, thalamus, hippocampus, cerebellum and medulla, and is also found in lung and testis. Testican-2 is unique in that it actually abolishes the inhibition of MT-MMPs by other testican family members and specifically inactivates N-Tes by binding to its COOH-terminal extracellular calcium-binding domain. Testican-2 halts neurite growth from cerebellar neurons and may be involved in regu-lating the development of the CNS.
