Abstract 320: Procollagen C-Endopeptidase Enhancer Protein 2 Enhances SR-BI Mediated HDL Cholesterol Uptake and Reduces Atherosclerosis in Mice
Epidemiological studies have shown an inverse correlation between plasma high density lipoprotein (HDL) concentrations and cardiovascular disease risk. At variance with these observations, clinical trials that significantly raised plasma HDL-C levels did not have improved clinical outcomes, emphasizing the importance of understanding HDL function. Recently, a significant correlation has been reported between human procollagen c-endopeptidase enhancer protein 2 (PCPE2) single nucleotide polymorphisms and HDL. PCPE2, a 52 kDa glycoprotein found in the extracellular matrix enhances cleavage of C-terminal procollagen by bone morphogenetic protein 1. Mice lacking PCPE2 have elevated concentrations of enlarged plasma HDL, a phenomenon associated with defective cholesterol efflux. HDL synthesis depends on ABCA1-mediated lipid efflux to lipid-poor apoA-I balanced by cholesterol uptake through hepatic scavenger receptor class B type I (SR-BI). Our studies focused on investigating if the elevated concentration of enlarged plasma HDL in PCPE2 deficient mice was atheroprotective. PCPE2 deficient mice were crossed with LDLr-/- mice (SKO) giving LDLr-/-, PCPE2-/- (DKO) mice that had elevated HDL levels compared to SKO mice. Despite elevated HDL levels, we found that DKO mice had significantly more lipid and CD68+ infiltration into the aortic root, similar to that reported for LDLr-/-, apoA-I-/- mice that lack plasma apoA-I/HDL. Furthermore, DKO mice showed reduced HDL apoA-I fractional clearance and reverse cholesterol transport rates compared to SKO mice suggesting PCPE2 plays a significant role in HDL remodeling and/or cholesterol uptake by the liver. To test the effect of PCPE2 on SR-BI function we incubated 3H-cholesteryl ether (3H-CE) enriched HDL from SKO and DKO mice with CHO cells overexpressing PCPE2. Compared to CHO control cells, overexpression of PCPE2 increased 3H-CE HDL uptake that was independent of HDL particle origin. Western Blot analysis showed no difference in SR-BI expression between control and PCPE2 transfected cells, suggesting that PCPE2 enhanced SR-BI function and promoted HDL cholesterol ester uptake. We conclude that PCPE2 is atheroprotective and an essential component of the reverse cholesterol transport system.
Author Disclosures: R.D. Pollard: None. C.N. Blesso: None. M. Zabalawi: None. B. Fulp: None. M. Gerelus: None. E.L. Lyons: None. X. Zhu: None. N. Nuradin: None. X. Li: None. O.L. Francone: None. D. Sahoo: None. M.J. Thomas: None.
- © 2015 by American Heart Association, Inc.