The β-subunit of ATP synthase is involved in cellular uptake and resecretion of apoA-I but does not control apoA-I-induced lipid efflux in adipocytes.
Cellular uptake and resecretion of apoA-I (apoA-I recycling) could be an important factor in determining the circulating plasma levels of apoA-I and/or HDL. Using a novel method to study protein recycling, we have recently demonstrated recycling of apoA-I by adipocytes and suggested that this is a receptor mediated process independent of ABCA1 function. In the present study, it is shown that apoA-I recycling by adipocytes can be blocked by a monoclonal antibody against the β-subunit of ATP synthase, a protein that had been previously identified as an apoA-I receptor. Investigation of the cellular recycling of two other proteins, an apolipoprotein and a small globular protein, showed that recycling of apoA-I is a selective process. The present study also shows that blocking apoA-I recycling has no effect on the rate of apoA-I-induced cholesterol or phospholipid efflux. It is concluded that cellular recycling of apoA-I is a selective process that involves the ectopically expressed β-subunit of ATP synthase. The physiological function of apoA-I recycling remains to be elucidated. However, this study shows that the process of apoA-I uptake and resecretion is not required for apoA-I lipidation.
Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, OK 74078, USA.
Alisha D
AD
Howard
Philip B
PB
Verghese
Estela L
EL
Arrese
Jose L
JL
Soulages
D041721:3T3-L1 Cells; D017667:Adipocytes / Q000201:enzymology*; D000818:Animals; D000911:Antibodies, Monoclonal; D016632:Apolipoprotein A-I / Q000235:genetics / Q000378:metabolism*; D001053:Apolipoproteins / Q000235:genetics / Q000378:metabolism; D002784:Cholesterol / Q000378:metabolism*; D054751:Cyclic AMP-Dependent Protein Kinase Catalytic Subunits / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D051379:Mice; D025261:Mitochondrial Proton-Translocating ATPases / Q000276:immunology / Q000378:metabolism*; D010743:Phospholipids / Q000378:metabolism*; D021381:Protein Transport; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013879:Thioredoxins / Q000378:metabolism; D014162:Transfection
C505693:APOA1 protein, human; D000911:Antibodies, Monoclonal; D016632:Apolipoprotein A-I; D001053:Apolipoproteins; D010743:Phospholipids; D011993:Recombinant Fusion Proteins; C042470:apolipophorin III; D013879:Thioredoxins; D002784:Cholesterol; D054751:Cyclic AMP-Dependent Protein Kinase Catalytic Subunits; C530489:ATP5b protein, mouse; D025261:Mitochondrial Proton-Translocating ATPases