A neutralizing APOA5 monoclonal antibody reduces amounts of lipoprotein lipase in capillaries and triggers hypertriglyceridemia
Abstract
Apolipoprotein AV (APOA5) regulates intravascular triglyceride metabolism by binding to the angiopoietin-like protein 3/8 complex (ANGPTL3/8) and suppressing its ability to unfold the native conformation of lipoprotein lipase (LPL). LPL unfolding results in loss of catalytic activity and the detachment of LPL from the surface of cells. An APOA5 truncation mutation (identified in two patients with hypertriglyceridemia) had suggested that the last 35 amino acids of APOA5 are important for its function. We reasoned that a monoclonal antibody (mAb) against carboxyl-terminal sequences in APOA5 could clarify functionally important amino acid residues in APOA5 and assist in elucidating the mechanism by which APOA5 regulates plasma triglyceride metabolism. Because carboxyl-terminal APOA5 sequences are evolutionarily conserved, we began by screening a human Fab bacteriophage library for binders of carboxyl-terminal APOA5 sequences. We identified one such binder and used phage DNA sequences to build a chimeric IgG 1 mAb (IBA707) against APOA5. The binding of IBA707 to APOA5 was abolished by nonconservative amino acid substitutions in conserved sequences (residues L337–I348) within a C-terminal α-helix in APOA5. The same substitutions disrupted APOA5’s ability to bind and inhibit ANGPTL3/8 activity. IBA707-mediated blockade of APOA5 function reduced intracapillary LPL levels and triggered elevated plasma levels of triglycerides and ANGPTL3/8 in both fasted and refed mice. IBA707 was cleared rapidly from the plasma in Apoa5 +/+ mice but slowly in Apoa5 –/– mice. Our studies identified functionally important amino acids in APOA5 and revealed that APOA5 controls plasma triglyceride metabolism in part by modulating plasma levels of ANGPTL3/8.
Article Details
Journal Info
Proceedings of the National Academy of Sciences
National Academy of Sciences
Authors (24)
Ye Yang
Anne P. Beigneux
Department of Medicine, David Geffen School of Medicine, University of California at Los Angeles
Troy L. Lowe
Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles
Yan Q. Chen
Lilly Research Laboratories, Eli Lilly and Company
Katherine Xie
Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles
Hyesoo Jung
Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles
Yiping Tu
Department of Medicine, David Geffen School of Medicine, University of California at Los Angeles
Rachel G. Yu
Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles
Julia L. Scheithauer
Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles
Shailen Mehta
Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles
Jerry Wu
Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles
Lindsay Alvarez
Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles
W. Sean Davidson
Gabriel Birrane
Division of Experimental Medicine, Beth Israel Deaconess Medical Center
Alan T. Remaley
Laboratory of Lipoprotein Metabolism, Translational Vascular Medicine Branch, National Heart, Lung, and Blood Institute, NIH
Denis Sviridov
Laboratory of Lipoprotein Metabolism, Translational Vascular Medicine Branch, National Heart, Lung, and Blood Institute, NIH
Michael Ploug
Finsen Laboratory, Copenhagen University Hospital - Rigshospitalet
Eugene Y. Zhen
Lilly Research Laboratories, Eli Lilly and Company
Yuewei Qian
Lilly Research Laboratories, Eli Lilly and Company
John H. Sloan
Lilly Research Laboratories, Eli Lilly and Company
Robert W. Siegel
Laboratory for Experimental Medicine, Lilly Research Laboratories, Eli Lilly and Company
Robert J. Konrad
Lilly Research Laboratories, Eli Lilly and Company
Loren G. Fong
Department of Medicine, David Geffen School of Medicine, University of California Los Angeles
Stephen G. Young
Department of Medicine, David Geffen School of Medicine, University of California Los Angeles