| abstract |
EF-hand, extracellular calcium-binding (EC) motif, found in secreted protein acidic and rich in cysteine (SPARC) and similar proteins. This family includes secreted protein acidic and rich in cysteine (SPARC), secreted protein, acidic and rich in cysteine-like 1 (SPARCL1), and similar proteins. SPARC is a prototypic collagen-binding matricellular protein that is involved in extracellular matrix (ECM) assembly and fibrosis through binding both fibrillar collagen and basal lamina collagen IV. It regulates the activity of matrix metalloproteinases (MMPs), as well as the growth factor signaling mediated by cell surface receptors including vascular endothelial growth factor (VEGF) receptor, basic fibroblast growth factor (bFGF), and transforming growth factor (TGF) beta1. It also shows survival activity in tumor progression. SPARC contains an N-terminal acidic 52-residue segment followed by a follistatin-like (FS) domain, and an alpha-helical EC domain with 2 unusual calcium-binding EF-hands and the collagen-binding site. SPARCL1 is the closest family member to SPARC. It shares the three primary domains contained within SPARC with an expanded N-terminal domain. SPARCL1 may function as both a tumor suppressor and as a regulator of angiogenesis. It can bind to collagens and be counter-adhesive to wild-type dermal fibroblasts, but do not influence rates of cell proliferation. Moreover, SPARCL1 can influence central nervous system (CNS) development and synaptic rearrangement. |