ABSTRACT
ABCG1 is an ATP binding cassette (ABC) transporter that removes excess cholesterol from peripheral tissues. Despite its role in preventing lipid accumulation and the development of cardiovascular and metabolic disease, the mechanism underpinning ABCG1-mediated cholesterol transport is unknown. Here we report a cryo-EM structure of human ABCG1 at 4 Å resolution in an inward-open state, featuring sterol-like density in the binding cavity. Structural comparison with the multidrug transporter ABCG2 and the sterol transporter ABCG5/G8 reveals the basis of mechanistic differences and distinct substrate specificity. Benzamil and taurocholate inhibited the ATPase activity of liposome-reconstituted ABCG1, whereas the ABCG2 inhibitor Ko143 did not. Based on the structural insights into ABCG1, we propose a mechanism for ABCG1-mediated cholesterol transport.
Subject(s)
ATP Binding Cassette Transporter, Subfamily G, Member 1/chemistry , ATP Binding Cassette Transporter, Subfamily G, Member 2/chemistry , Adenosine Triphosphate/chemistry , Amiloride/analogs & derivatives , Cholesterol/chemistry , Neoplasm Proteins/chemistry , Taurocholic Acid/pharmacology , ATP Binding Cassette Transporter, Subfamily G, Member 1/antagonists & inhibitors , ATP Binding Cassette Transporter, Subfamily G, Member 1/genetics , ATP Binding Cassette Transporter, Subfamily G, Member 1/metabolism , ATP Binding Cassette Transporter, Subfamily G, Member 2/antagonists & inhibitors , ATP Binding Cassette Transporter, Subfamily G, Member 2/genetics , ATP Binding Cassette Transporter, Subfamily G, Member 2/metabolism , ATP Binding Cassette Transporter, Subfamily G, Member 5/antagonists & inhibitors , ATP Binding Cassette Transporter, Subfamily G, Member 5/chemistry , ATP Binding Cassette Transporter, Subfamily G, Member 5/genetics , ATP Binding Cassette Transporter, Subfamily G, Member 5/metabolism , ATP Binding Cassette Transporter, Subfamily G, Member 8/antagonists & inhibitors , ATP Binding Cassette Transporter, Subfamily G, Member 8/chemistry , ATP Binding Cassette Transporter, Subfamily G, Member 8/genetics , ATP Binding Cassette Transporter, Subfamily G, Member 8/metabolism , Adenosine Triphosphate/metabolism , Amiloride/chemistry , Amiloride/pharmacology , Amino Acid Sequence , Binding Sites , Biological Transport/drug effects , Cholesterol/metabolism , Cryoelectron Microscopy , Diketopiperazines/chemistry , Diketopiperazines/pharmacology , Gene Expression , HEK293 Cells , Heterocyclic Compounds, 4 or More Rings/chemistry , Heterocyclic Compounds, 4 or More Rings/pharmacology , Humans , Kinetics , Lipoproteins/antagonists & inhibitors , Lipoproteins/chemistry , Lipoproteins/genetics , Lipoproteins/metabolism , Models, Molecular , Neoplasm Proteins/antagonists & inhibitors , Neoplasm Proteins/genetics , Neoplasm Proteins/metabolism , Protein Binding , Protein Conformation, alpha-Helical , Protein Conformation, beta-Strand , Protein Interaction Domains and Motifs , Recombinant Proteins/chemistry , Recombinant Proteins/genetics , Recombinant Proteins/metabolism , Sequence Alignment , Sequence Homology, Amino Acid , Substrate Specificity , Taurocholic Acid/chemistryABSTRACT
Atherosclerosis (AS) is a risky cardiovascular disease with limited treatment options. Various pan or type-selective histone deacetylase (HDAC) inhibitors are reportedly atheroprotective against atherosclerosis (AS); however, the key effectors and the main cellular processes that mediate the protective effects remain poorly defined. Here, we report that PPARγ (Peroxisome proliferator-activated receptor gamma), a transcription factor actively involved in lipid metabolism with strong tissue protective and anti-inflammation properties, is a critical mediator of the anti-AS effects by HDAC inhibition. We showed that a well-known pan-HDAC inhibitor TSA (Trichostatin A) reduced foam cell formation of macrophages that is accompanied by a marked elevation of PPARγ and its downstream cholesterol efflux transporter ABCA1 (ATP-binding membrane cassette transport protein A1) and ABCG1. In an AS model of ApoE-/- mice fed on high-fat diet, TSA treatment alleviated AS lesions, similarly increased PPARγ and the downstream cholesterol transporters and mitigated the induction of inflammatory cytokine TNFα and IL-1ß. Exploring the potential cause of PPARγ elevation revealed that TSA induced the acetylation of C/EBPα (CCAAT enhancer binding protein alpha), the upstream regulator of PPARγ, through which it increased PPARγ transactivation. More importantly, we generated a strain of PPARγ/ApoE double knockout mice and demonstrated that lack of PPARγ abrogated the protective effects of TSA on foam cell formation of peritoneal macrophages and the AS pathogenesis. Taken together, these results unravel that C/EBPα and PPARγ are the HDAC-sensitive components of an epigenetic signaling pathway mediating foam cell formation and AS development, and suggest that targeting C/EBPα/PPARγ axis by HDAC inhibitors possesses therapeutic potentials in retarding the progression of AS and the related cardiovascular diseases.
