The N-terminus of apolipoprotein B mediates the interaction of atherogenic lipoproteins with endothelial cells
Ainara G. Cabodevilla, Camila Calistru, Waqas Younis, Dimitris Nasias, Tse W.W. Ho, Narasimha Anaganti, Swati Valmiki, Sujith Rajan, Jana Gjini, Rufina Kore, Carmen Hannemann, Nicholas O. Davidson, Tomas Vaisar, Jenny E. Kanter, Karin E. Bornfeldt, Edward A. Fisher, Warren L. Lee, Tobias Madl, M. Mahmood Hussain, Ira J. Goldberg
Ainara G. Cabodevilla, Camila Calistru, Waqas Younis, Dimitris Nasias, Tse W.W. Ho, Narasimha Anaganti, Swati Valmiki, Sujith Rajan, Jana Gjini, Rufina Kore, Carmen Hannemann, Nicholas O. Davidson, Tomas Vaisar, Jenny E. Kanter, Karin E. Bornfeldt, Edward A. Fisher, Warren L. Lee, Tobias Madl, M. Mahmood Hussain, Ira J. Goldberg
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Research Article Metabolism Vascular biology

The N-terminus of apolipoprotein B mediates the interaction of atherogenic lipoproteins with endothelial cells

Abstract

Apolipoprotein B–containing (APOB-containing) lipoproteins contribute to atherosclerosis by entering the arterial wall through the endothelial cell (EC) surface receptors scavenger receptor-BI (SR-BI) and activin receptor-like kinase 1 (ALK1). We used N-terminal fragments of APOB, molecular modeling, and site-directed mutagenesis to identify and block the binding of chylomicrons and LDL to these receptors in cells and mice. We discovered that different APOB regions interact with SR-BI and ALK1 expressed on ECs. APOB48 lipoproteins were only internalized by SR-BI. A fragment of APOB comprising 18% of the N-terminal sequence, APOB18, reduced the uptake and transport of both chylomicrons and LDL by ECs, whereas a shorter fragment, APOB12, only blocked ALK1-mediated uptake of APOB100-containing lipoproteins. Importantly, overexpressing APOB18 decreased atherosclerosis in hypercholesterolemic mice. These findings identify the N-terminal region of APOB as the cause of atherosclerosis and illustrate an approach to treating or preventing vascular disease.

Authors

Ainara G. Cabodevilla, Camila Calistru, Waqas Younis, Dimitris Nasias, Tse W.W. Ho, Narasimha Anaganti, Swati Valmiki, Sujith Rajan, Jana Gjini, Rufina Kore, Carmen Hannemann, Nicholas O. Davidson, Tomas Vaisar, Jenny E. Kanter, Karin E. Bornfeldt, Edward A. Fisher, Warren L. Lee, Tobias Madl, M. Mahmood Hussain, Ira J. Goldberg

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Figure 3

Molecular modeling and mutational studies of APOB18 complexes.

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Molecular modeling and mutational studies of APOB18 complexes. (A and B)...
(A and B) AlphaFold 2 predictions of the APOB18–SR-BI (A) and APOB18-ALK1 (B) complex structures. For all AlphaFold 2 predictions, an overlay of 5 independent calculations is shown. The binding interfaces of SR-BI and ALK1 on the surface of APOB18 are visualized by coloring all residues within APOB18, which are within 5 Å distance of SR-BI and ALK1. Note that the ALK1 binding interface appears more extensive due to the nonconvergence of the structural models. (C) Display of surface-exposed hydrophobic residues selected for mutational studies. (D) ECs were deprived of serum overnight, then incubated with DiI-labeled chylomicrons (4 mg/dL) in serum-free medium and in the presence of control, WT, or mutant APOB18, as indicated. DiI-chylomicron uptake was strongly and similarly inhibited by WT, L682, and L687 APOB18 (≈80% inhibition). (E) In contrast, L645G APOB18 was less potent in inhibiting CM uptake, and W721G mutation completely blunted CM uptake inhibition. (F) The inhibitory efficiency of mutant APOB18 fragments significantly correlates with their ability to associate with the EC surface. (G and H) Representative images of 4 independent competition (G) and membrane association studies (H), each performed with 3 biological replicates. Scale bars, 10 μm (G), 20 μm (H). *P < 0.01, **P < 0.001, ****P < 0.00001, 1-way ANOVA followed by Dunnett’s post hoc multiple-comparison test against control.