ultured according to the manufacturer’s manual. Briefly, human ASC were cultured in ASC growth medium containing basal medium, growth supplement and 2 mmol/L L-glutamine. The 12409010 cultures were maintained in a humidified atmosphere of 5% CO2 and 95% air at 37uC. The medium was replaced every 23 days. Passages 56 were used for all experiments. To initiate differentiation, two days post-confluent ASC were treated with a differentiation medium containing ASC basal medium, 10% FBS, 2 mmol/L Lglutamine, 1 mmol/L dexamethasone, 10 mmol/L insulin, 0.5 mmol/L IBMX, 200 mmol/L Indomethacin, 100 U/ml penicillin and 100 ug/ml streptomycin. The differentiation medium was changed every three days thereafter until the indicated times. Transfection of siRNA in 3T3-L1 cells One day before transfection, 3T3-L1 cells were seeded in the growth medium without antibiotics so that they would be 5070% confluent at the time of transfection. Cells were transfected with 10 nmol/L siRNA using Lipofectamine RNAiMAX, according to the manufacturer’s protocol. A universal siRNA Control was used as the negative control. All siRNAs were obtained from Invitrogen. Oil Red O staining Oil red O staining was performed as suggested by the manufacturer with minor modifications. Seven days after the induction of adipocyte differentiation, 3T3-L1 cells in 60 mm dishes were washed with PBS and fixed with 10% formalin. The dishes were washed once with 60% isopropanol and left to dry completely. The cells were then stained in 0.2% Oil Red O for 10 minutes, rinsed with 60% isopropanol once, and thoroughly washed with water four times. The dishes were subsequently scanned to get the pictures. After extracting the Oil Red O with 100% isopropanol, the extracted dye was quantified on a spectrophotometer by reading the absorbance at 510 nm wave length. Immunoblotting Cells were lysed in mammalian protein extraction reagent supplemented with protease inhibitor cocktail. Additionally, phosphatase inhibitor cocktail I and II were added for phospho-ERK detection. The cell lysates were resolved by electrophoresis on 10% or 412% precast Bis-Tris gel. Proteins were transferred from the gel to a BioPQQ web nitrocellulose membrane using the iBlot Dry Blotting System. Specific proteins were detected by immunoblotting 8632751 using primary antibodies anti-PHB1, 
anti-PHB2, anti-C/EBPb, anti-PPARc, anti-aP2, anti-HSP90 anti-b-actin, anti-ERK, anti-p-ERK and anti-porin. Horseradish peroxidase -conjugated anti-rabbit IgG and anti-mouse IgG were used as secondary antibodies in a 6-well plate. 3T3-L1 cells were seeded and treated with differentiation medium in the plate as described above. The cells were then fixed with 4% paraformaldehyde in PBS for 30 min, Prohibitins Are Required for Adipogenesis followed by PBS wash and subsequent treatment with cold absolute methanol for 5 min at 220uC. The cells were rinsed with PBS and permeabilized with 0.2% Triton X-100 in PBS for 10 min. After blocking with 5% BSA in PBS for 1 hour, the cover glasses were incubated with anti-PHB1, antiPHB2 or anti-Cytochrome C antibody in 0.1% BSA in PBS at room temperature for two hours. The cells were then washed with PBS and incubated with Rhodamine or Alexa Fluor 488 conjugated secondary antibody in 0.1% BSA in PBS at room temperature for 1 hour. Thereafter, the cover glasses were mounted upside down on microscope slides containing mounting medium. The mounted slides were examined under an Olympus BX41 microscope equipped with an Optronics Magnaf
