Dataset Information

V-ATPase (Vacuolar ATPase) Activity Required for ABCA1 (ATP-Binding Cassette Protein A1)-Mediated Cholesterol Efflux.

ABSTRACT: Objective- We have shown that ABCA1 (ATP-binding cassette protein A1) mediates unfolding of the apoA1 (apolipoprotein A1) N-terminal helical hairpin during apoA1 lipidation. Others have shown that an acidic pH exposes the hydrophobic surface of apoA1. We postulated that the V-ATPase (vacuolar ATPase) proton pump facilitates apoA1 unfolding and promotes ABCA1-mediated cholesterol efflux. Approach and Results- We found that V-ATPase inhibitors dose-dependently decreased ABCA1-mediated cholesterol efflux to apoA1 in baby hamster kidney cells and RAW264.7 cells; and similarly, siRNA knockdown of ATP6V0C inhibited ABCA1-mediated cholesterol efflux to apoA1 in RAW264.7 cells. Although ABCA1 expression did not alter total cellular levels of V-ATPase, ABCA1 increased the cell surface levels of the V0A1 and V1E1 subunits of V-ATPase. We generated a fluorescein isothiocyanate/Alexa647 double-labeled fluorescent ratiometric apoA1 pH indicator whose fluorescein isothiocyanate/Alexa647 emission ratio decreased as the pH drops. We found that ABCA1 induction in baby hamster kidney cells led to acidification of the cell-associated apoA1 pH indicator, compared with control cells without ABCA1 expression. The V-ATPase inhibitor bafilomycin A1 dose-dependently inhibited the apoA1 pH shift in ABCA1-expressing cells, without affecting the levels of cell-associated apoA1. However, we were not able to detect ABCA1-mediated extracellular proton release. We showed that acidic pH facilitated apoA1 unfolding, apoA1 solubilization of phosphatidycholine:phosphatidyserine liposomes, and increased lipid fluidity of these liposomes. Conclusions- Our results support a model that ABCA1 recruits V-ATPase to the plasma membrane where V-ATPase mediates apoA1 acidification and membrane remodeling that promote apoA1 unfolding and ABCA1-mediated HDL (high-density lipoprotein) biogenesis and lipid efflux.

SUBMITTER: Lorkowski SW

PROVIDER: S-EPMC6209108 | biostudies-literature | 2018 Nov

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

V-ATPase (Vacuolar ATPase) Activity Required for ABCA1 (ATP-Binding Cassette Protein A1)-Mediated Cholesterol Efflux.

Lorkowski Shuhui Wang SW Brubaker Gregory G Gulshan Kailash K Smith Jonathan D JD

Arteriosclerosis, thrombosis, and vascular biology 20181101 11

Objective- We have shown that ABCA1 (ATP-binding cassette protein A1) mediates unfolding of the apoA1 (apolipoprotein A1) N-terminal helical hairpin during apoA1 lipidation. Others have shown that an acidic pH exposes the hydrophobic surface of apoA1. We postulated that the V-ATPase (vacuolar ATPase) proton pump facilitates apoA1 unfolding and promotes ABCA1-mediated cholesterol efflux. Approach and Results- We found that V-ATPase inhibitors dose-dependently decreased ABCA1-mediated cholesterol ...[more]

PMID: 30354238

Similar Datasets

Project description:ObjectivesCholesterol efflux capacity (CEC) is the main antiatherogenic function of high-density lipoprotein (HDL). ATP-binding-cassette A1 (ABCA1) membrane transporter initiates cholesterol export from arterial macrophages to pre-β HDL particles fostering their maturation; in turn, those accept cholesterol through ABCG1-mediated export. Impaired pre-β HDL maturation may disrupt the collaborative function of the two transporters and adversely affect atherosclerosis. Statins exert atheroprotective functions systemically and locally on plaque. We here evaluated associations between ABCA1-CEC, coronary atherosclerosis and cardiovascular risk and the influence of statins on those relationships in rheumatoid arthritis (RA).MethodsEvaluation with computed tomography angiography was undertaken in 140 patients and repeated in 99 after 6.9 ± 0.3 years. Events comprising cardiovascular death, acute coronary syndromes, stroke, claudication, revascularization and heart failure were recorded. ABCA1-CEC and ABCG1-CEC were evaluated in J774A.1 macrophages and Chinese hamster ovary (CHO) cells respectively and expressed as percentage of effluxed over total intracellular cholesterol. Covariates in all cardiovascular event risk and plaque outcome models included atherosclerotic cardiovascular disease (ASCVD) risk score and high-density lipoprotein cholesterol.ResultsABCA1-CEC negatively correlated with ABCG1-CEC (r = -0.167, p = 0.049). ABCA1-CEC associated with cardiovascular risk (adjusted hazard ratio 2.05 [95%CI 1.20-3.48] per standard deviation [SD] increment). There was an interaction of ABCA1-CEC with time-varying statin use (p = 0.038) such that current statin use inversely associated with risk only in patients with ABCA1-CEC below the upper tertile. ABCA1-CEC had no main effect on plaque or plaque progression; instead, ABCA1-CEC (per SD) associated with fewer baseline total plaques (adjusted rate ratio [aRR] 0.81, [95%CI 0.65-1.00]), noncalcified plaques (aRR 0.78 [95%CI 0.61-0.98]), and vulnerable low-attenuation plaques (aRR 0.41 [95%CI 0.23-0.74]) in statin users, and more low-attenuation plaques (aRR 1.91 [95%CI 1.18-3.08]) in nonusers (p-for-interaction = 0.018, 0.011, 0.025 and < 0.001 respectively). Moreover, ABCA1-CEC (per SD) associated with greater partially/fully-calcified plaque progression (adjusted odds ratio 3.07 [95%CI 1.20-7.86]) only in patients not exposed to statins during follow-up (p-for-interaction = 0.009).ConclusionIn patients with RA, higher ABCA1-CEC may reflect a proatherogenic state, associated with enhanced cardiovascular risk. Statin use may unmask the protective impact of ABCA1-mediated cholesterol efflux on plaque formation, progression and cardiovascular risk.

Dataset Information

V-ATPase (Vacuolar ATPase) Activity Required for ABCA1 (ATP-Binding Cassette Protein A1)-Mediated Cholesterol Efflux.

Publications

V-ATPase (Vacuolar ATPase) Activity Required for ABCA1 (ATP-Binding Cassette Protein A1)-Mediated Cholesterol Efflux.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets