Antibody-mediated disruption of the interaction between PCSK9 and the low-density lipoprotein receptor

Abstract

PCSK9 (proprotein convertase subtilisin/kexin type 9) promotes degradation of the LDLR [LDL (low-density lipoprotein) receptor] through an as-yet-undefined mechanism, leading to a reduction in cellular LDLc (LDL-cholesterol) and a concomitant increase in serum LDLc. Central to the function of PCSK9 is a direct protein–protein interaction formed with the LDLR. In the present study, we investigated a strategy to modulate LDL uptake by blocking this interaction using specific antibodies directed against PCSK9. Studies using surface plasmon resonance demonstrated that direct binding of PCSK9 to the LDLR could be abolished with three different anti-PCSK9 antibodies. Two of these antibodies were raised against peptide epitopes in a region of the catalytic domain of PCSK9 that is involved in the interaction with the LDLR. Such antibodies restored LDL uptake in HepG2 cells treated with exogenous PCSK9 and in HepG2 cells engineered to overexpress recombinant PCSK9. This latter observation indicates that antibodies blocking the PCSK9–LDLR interaction can inhibit the action of PCSK9 produced endogenously in a cell-based system. These antibodies also disrupted the higher-affinity interaction between the natural gain-of-function mutant of PCSK9, D374Y, and the LDLR in both the cell-free and cell-based assays. These data indicate that antibodies targeting PCSK9 can reverse the PCSK9-mediated modulation of cell-surface LDLRs.

High-dose atorvastatin causes a rapid sustained increase in human serum PCSK9 and disrupts its correlation with LDL cholesterol

“…Rather, PCSK9 binds to the LDLR and subsequently targets it for lysosomal destruction within the hepatocyte ( 8,(19)(20)(21). This concept of how PCSK9 acts to decrease hepatic LDLR levels is supported by recent fi ndings that disruption of the binding of PCSK9 to the LDLR using anti-PCSK9 antibody results in preserved LDLR and decreased [22][23][24].Several different PCSK9 mutations have been reported in humans. Patients with gain-of-function mutations of PCSK9 present with severe familial hypercholesterolemia and accompanying increased cardiovascular risk (25)(26)(27)(28)(29).…”

Plasma levels of PCSK9 and phenotypic variability in familial hypercholesterolemia

“…These fi ndings, combined with the fact that decreased PCSK9 activity is associated with lower LDL-C levels and a reduced risk of coronary heart disease ( 18 ), support the inhibition of PCSK9 as a target of great signifi cance. In fact, several agents are already being investigated in humans (19)(20)(21)(22)(23)(24).…”

PCSK9 inhibition fails to alter hepatic LDLR, circulating cholesterol, and atherosclerosis in the absence of ApoE

“…Whether this disproportionate reduction in risk is due to PCSK9 having a direct negative effect at the atherosclerotic lesion or if the additional benefi t is driven by a modest lifelong reduction in serum cholesterol is unclear. These observations have led to the development of PCSK9 inhibitors as a means to therapeutically reduce LDL-C and the associated CVD risk (25)(26)(27)(28)(29). Inhibition of PCSK9 by monoclonal antibodies, adnectins, or siRNAs reduces LDL-C levels in patients, and clinical trials designed to assess the effect of anti-PCSK9 therapies on cardiovascular outcomes are underway (30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40)(41)(42).…”