Chaperone-like activity revealed in the matricellular protein SPARC

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. © 2006 Wiley‐Liss, Inc.