GPIHBP1 stabilizes lipoprotein lipase and prevents its inhibition by angiopoietin-like 3 and angiopoietin-like 4

Abstract

Glycosylphosphatidylinositol-anchored HDL-binding protein (GPIHBP1) binds both LPL and chylomicrons, suggesting that GPIHBP1 is a platform for LPL-dependent processing of triglyceride (TG)-rich lipoproteins. Here, we investigated whether GPIHBP1 affects LPL activity in the absence and presence of LPL inhibitors angiopoietin-like (ANGPTL)3 and ANGPTL4. Like heparin, GPIHBP1 stabilized but did not activate LPL. ANGPTL4 potently inhibited nonstabilized LPL as well as heparinstabilized LPL but not GPIHBP1-stabilized LPL. Like ANGPTL4, ANGPTL3 inhibited nonstabilized LPL but not GPIHBP1-stabilized LPL. ANGPTL3 also inhibited heparinstabilized LPL but with less potency than nonstabilized LPL. Consistent with these in vitro findings, fasting serum TGs of Angptl4-/- Gpihbp1-/- mice were lower than those of Gpihbp1-/- mice and approached those of wild-type littermates. In contrast, serum TGs of Angptl3-/-/ Gpihbp1-/- mice were only slightly lower than those of Gpihbp1-/- mice. Treating Gpihbp1-/- mice with ANGPTL4- or ANGPTL3-neutralizing antibodies recapitulated the double knockout phenotypes. These data suggest that GPIHBP1 functions as an LPL stabilizer. Moreover, therapeutic agents that prevent LPL inhibition by ANGPTL4 or, to a lesser extent, ANGPTL3, may benefit individuals with hyperlipidemia caused by gene mutations associated with decreased LPL stability. Copyright © 2009 by the American Society for Biochemistry and Molecular Biology, Inc.