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Purification and characterization of clusterin (APOJ) : the role of clusterin in brain function and neurodegeneration
Clusterin is a multi-functional protein that was initially isolated from ram testis. It was first identified for its ability to promote aggregation of cells, hence the name clusterin (Fritz et al., 1983). Subsequent research has identified clusterin in many mammalian fluids and organ systems. A number of functions have been hypothesized for clusterin from independent labs which produced a variety of acronyms. For example, clusterin has been shown to protect cells from the innate immune response such as complement mediated lysis , complement lysis inhibitor, CLI (Oda et al., 1995) and is also involved in cholesterol transport, ApolipoproteinJ, Apoj , (Gelisseb et al., 1998). It is the major secretory product from sperm cells (sulfated glycoprotein 2,SGP-2). It is also known as Testosterone repressed prostate message (TRPM) due to the fact that it is up- regulated after castration and is involved in apoptosis. The role of clusterin as a neuroprotectant has been investigated, however, data supporting a neuroprotective role remain under debate. In this report we combined immunoaffinity chromatography with HPLC to purify clusterin from human serum. We also utilized a clusterin knock-out model to determine the role of clusterin under toxic insults. A recombinant protein purification protocol was also developed.