Chaperone‐like activity revealed in the matricellular protein SPARC

Abstract
SPARC (Secreted Protein, Acidic and Rich in Cysteine) is a matricellular glycoprotein that modulates cell proliferation, adhesion, migration, and extracellular matrix (ECM) production. In this report chaperone-like activity of SPARC was identified in a thermal aggregation assay in vitro. Ultraviolet circular dichroism (UVCD) spectroscopy determined that SPARC was stable at temperatures up to 50°C. Unfolding and aggregation of the chaperone target protein, alcohol dehydrogenase (ADH), were initiated at 50°C. SPARC inhibited the thermal aggregation of ADH in a concentration-dependent manner, with maximal inhibition at a 1:4 molar ratio of SPARC:ADH. Synergy between the chaperone-like activities of SPARC and αB-crystallin, a small heat shock protein and molecular chaperone in the lens, was observed in SPARC-αB-crystallin double −/− mice. J. Cell. Biochem. 98: 701–705, 2006.