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Journal of Lipid Research, Vol. 50, S150-S155, April 2009
Copyright © 2009 by American Society for Biochemistry and Molecular Biology

Lipoprotein Metabolism

The ins (cell) and outs (plasma) of apolipoprotein A-V

Trudy M. Forte^1,*, Xiao Shu^*, and Robert O. Ryan^*,

^* Center for Prevention of Obesity, Diabetes, and Cardiovascular Disease, Children's Hospital Oakland Research Institute, Oakland, CA 94609
Department of Nutritional Sciences and Toxicology, University of California, Berkeley, CA 94720

Work from the authors' laboratory was supported by a grant from the National Institutes of Health (HL-73061). X.S. is a recipient of the Americal Heart Association Western States Affiliate Predoctoral Fellowship.

Published, JLR Papers in Press, December 2, 2008.

¹ To whom correspondence should be addressed. e-mail: tforte{at}chori.org

ABSTRACT

Apolipoprotein A-V (apoA-V) has a close interrelationship with plasma triglyceride (TG). Since the discovery of the apoA-V gene in 2001, we have learned that single nucleotide polymorphisms in this gene correlate with altered plasma TG levels in humans, while genetically engineered mice manifest unique TG phenotypes. Studies of recombinant apoA-V protein have revealed that it is composed of two independently folded structural domains. The C-terminal domain possesses high lipid binding affinity, while the N-terminal domain adopts a helix bundle molecular architecture. A sequence element with high positive charge character, between residues 185 and 228, functions in binding of apoA-V to heparan sulfate proteoglycans as well as to members of the low-density lipoprotein receptor family and glycosylphosphatidylinositol high-density lipoprotein binding protein1. These interactions may be related to the capacity of this protein to regulate TG levels. ApoA-V is poorly secreted from transfected cultured hepatoma cell lines and is present in plasma at exceedingly low levels. Studies of apoA-V intracellular trafficking revealed an association with cytosolic lipid droplets. Thus, it is conceivable that apoA-V may also modulate TG metabolism within the cell. Much remains to be learned about this fascinating yet confounding member of the class of exchangeable apolipoproteins.

Supplementary key words apolipoprotein A-V molecular structure • apolipoprotein A-V mutants • apolipoprotein A-V lipid binding • heparan sulfate proteoglycans • apolipoprotein A-V intracellular trafficking • apolipoprotein A-V lipid droplet association

Abbreviations: ADRP, adipocyte differentiation-related protein; apo, apolipoprotein; ER, endoplasmic reticulum; GPIHBP1, glycosylphosphatidylinositol high-density lipoprotein binding protein1; HSPG, heparan sulfate proteoglycan; HTG, hypertriglyceridemia; LDLR, LDL receptor; LRP, LDL receptor-related protein; SNP, single nucleotide polymorphism; TG, triglyceride

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