Dominant and sensitive control of oxidative flux by the ATP-ADP carrier in human skeletal muscle mitochondria: Effect of lysine acetylation.

The adenine nucleotide translocase (ANT) of the mitochondrial inner membrane exchanges ADP for ATP. Mitochondria were isolated from human vastus lateralis muscle (n = 9). Carboxyatractyloside titration of O2 consumption rate (Jo) at clamped [ADP] of 21 µM gave ANT abundance of 0.97 ±â€¯0.14 nmol ANT/mg and a flux control coefficient of 82% ±â€¯6%. Flux control fell to 1% ±â€¯1% at saturating (2 mM) [ADP]. The KmADP for Jo was 32.4 ±â€¯1.8 µM. In terms of the free (-3) ADP anion this KmADP was 12.0 ±â€¯0.7 µM. A novel luciferase-based assay for ATP production gave KmADP of 13.1 ±â€¯1.9 µM in the absence of ATP competition. The free anion KmADP in this case was 2.0 ±â€¯0.3 µM. Targeted proteomic analyses showed significant acetylation of ANT Lysine23 and that ANT1 was the most abundant isoform. Acetylation of Lysine23 correlated positively with KmADP, r = 0.74, P = 0.022. The findings underscore the central role played by ANT in the control of oxidative phosphorylation, particularly at the energy phosphate levels associated with low ATP demand. As predicted by molecular dynamic modeling, ANT Lysine23 acetylation decreased the apparent affinity of ADP for ANT binding.

Simplified culture techniques for growth and differentiation of murine and human pre-adipocytes for translational applications.

BACKGROUND: Adipose tissue has become a promising source of adult stem cells. Looking for optimal culture conditions, we evaluated the ability of L15, a free-gas exchange culture medium, to support cell proliferation and adipogenesis of murine 3T3-F442A and human normal (HNPA) and lipoma-derived (HLPA) pre-adipocytes. METHODS: 3T3-F442A, HNPA and HLPA cell proliferation were compared in short-term cultures and along multiple passages in Dulbecco's modified Eagle medium (DMEM) or DMEM-F12 under a 5% CO(2) atmosphere or L15 medium under a free-gas exchange atmosphere. Adipogenesis in these cells was evaluated by quantifying lipid accumulation and glycerol-3-phosphate dehydrogenase (GPDH) activity, and by assaying the expression of adipogenic markers by reverse transcriptase-polymerase chain reaction (RT-PCR). RESULTS: 3T3 pre-adipocytes grew at similar rates in serum-supplemented L15 or DMEM, but L15 induced higher colony-forming efficiency in these cells. HNPA and HLPA grew more actively in L15 than in DMEM-F12 for more than 10 successive passages and reached higher colony-forming efficiency in L15 medium. On the other hand, while high-glucose DMEM and L15 supplemented with glucose 1 g/L induced similar levels of 3T3 adipogenesis, L15 with no added glucose increased HNPA and HLPA adipogenesis with respect to DMEM-F12, as measured by lipid accumulation, GPDH activity and expression of adipogenic markers C/EBPalpha, GLUT-4, LPL and aP2. DISCUSSION: The free-gas exchange medium L15 supports cell proliferation and adipogenesis of murine 3T3 and normal and lipoma-derived human subcutaneous pre-adipocytes to a greater extent than DMEM or DMEM-F12. The routine use of L15 will optimize translational applications of adipose cells.