MOLECULAR ASPECTS OF APOPROTEIN J

Indu Verma*, Priyanka Joshi, Jasbir Singh, Rajesh Pandey, K. S. Sodhi

ABSTRACT

Apolipoprotein J (apoprotein J, apo J, clusterin) is a multifunctional protein normally associated with lipids in plasma and cerebrospinal fluid, and secreted as lipoparticles by hepatocytes and astrocytes. Apo J is abundant in numerous biological fluids including semen, urine, breast milk, plasma and cerebrospinal fluid. There are two major sources of apo J in the circulation: plasma, in which it is found associated with high-density lipoprotein (HDL) particles; and platelets, where it is a constituent of the α-granules. Apo J has been implicated in a wide range of physiological and pathophysiological processes, such as reverse lipid transport and redistribution, apoptosis, folding of damaged extracellular proteins (chaperone), cell adhesion and aggregation, membrane recycling, complement regulation, tissue remodeling, tumorigenesis and several age related diseases (e.g. atherosclerosis and Alzheimer‟s disease). In blood, complexes of apo J with apolipoprotein A-I and the human esterase paraoxonase regulate the transport and local redistribution of lipids. Serum apo J concentrations are increased in experimental models of diet-induced atherosclerosis, as well as in patients with diabetes mellitus or coronary heart disease. However, the pathophysiological role of apo J in atherosclerosis and the therapeutic implications merit further evaluation.

Keywords: Apolipoprotein J, clusterin, atherosclerosis, HDL, cardiovascular disease, plasma.