Extracellular ATP is generated by ATP synthase complex in adipocyte lipid rafts.
Mitochondrial biogenesis is known to accompany adipogenesis to complement ATP and acetyl-CoA required for lipogenesis. Here, we demonstrated that mitochondrial proteins such as ATP synthase alpha and beta, and cytochrome c were highly expressed during the 3T3-L1 differentiation into adipocytes. Fully-differentiated adipocytes showed a significant increase of mitochondria under electron microscopy. Analysis by immunofluorescence, cellular fractionation, and surface biotinylation demonstrated the elevated levels of ATP synthase complex found not only in the mitochondria but also on the cell surface (particularly lipid rafts) of adipocytes. High rate of ATP (more than 30 microM) synthesis from the added ADP and P(i) in the adipocyte media suggests the involvement of the surface ATP synthase complex for the extracellular ATP synthesis. In addition, this ATP synthesis was significantly inhibited in the presence of oligomycin, an ATP synthase inhibitor, and carbonyl cyanide m-chlorophenylhydrazone (CCCP), an ATP synthase uncoupler. Decrease of extracellular ATP synthesis in acidic but not in basic media further indicates that the surface ATP synthase may also be regulated by proton gradient through the plasma membrane.
Kim
Bong-Woo
BW
Graduate School of Life Sciences and Biotechnology, Korea University, Seoul 136-701, Korea.
Choo
Hyo-Jung
HJ
Lee
Joong-Won
JW
Kim
Ji-Hyun
JH
Ko
Young-Gyu
YG
D000255:Adenosine Triphosphate / Q000032:analysis / Q000096:biosynthesis*; D017667:Adipocytes / Q000201:enzymology* / Q000648:ultrastructure; D000818:Animals; D002454:Cell Differentiation / Q000502:physiology; D002462:Cell Membrane / Q000737:chemistry; D002478:Cells, Cultured; D006801:Humans; D021962:Membrane Microdomains / Q000737:chemistry / Q000201:enzymology*; D051379:Mice; D008928:Mitochondria / Q000378:metabolism / Q000648:ultrastructure; D025261:Mitochondrial Proton-Translocating ATPases / Q000032:analysis / Q000502:physiology*
D000255:Adenosine Triphosphate; D025261:Mitochondrial Proton-Translocating ATPases