Expression and regulation of neuronal apoptosis inhibitory protein during adipocyte differentiation.
We have used the 3T3-L1 and 3T3-F442A preadipocyte cell lines to examine the expression and regulation of neuronal apoptosis inhibitory protein (NAIP) during adipocyte differentiation. When 3T3-L1 preadipocytes differentiated into adipocytes, they developed resistance to apoptosis induced by growth factor deprivation, as assessed by terminal deoxynucleotide transferase (TdT)-mediated dUTP nick end labeling. Protein expression of NAIP was markedly elevated in 3T3-L1 and 3T3-F442A adipocytes compared with that in their fibroblast-like precursors. NAIP was also present in rat white adipocytes. In 3T3-L1 cells, the increase in NAIP occurred by day 4 of the 8-day differentiation protocol, which includes exposure of confluent preadipocytes to insulin, dexamethasone, and isobutylmethylxanthine. Incubation of confluent 3T3-L1 preadipocytes with any of these components alone had no effect on NAIP expression. When 3T3-C2 cells, a control cell line that does not differentiate, were subjected to the differentiation protocol, the low NAIP levels remained unaltered. Addition of rapamycin, a p70 S6 kinase inhibitor that blocks adipocyte differentiation, to the 3T3-L1 differentiation medium prevented the rise in NAIP expression. These data demonstrate for the first time that NAIP is expressed in adipocyte cell lines and primary adipocytes. The differentiation-dependent augmentation of NAIP protein levels in 3T3-L1 adipocytes is closely correlated with the development of resistance to apoptosis induced by growth factor deprivation, suggesting a potential role for NAIP in these cells.
Magun
R
R
Department of Medicine and Biochemistry, Loeb Research Institute, Ottawa Hospital, Ontario, Canada.
Gagnon
A
A
Yaraghi
Z
Z
Sorisky
A
A
D016475:3T3 Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D017667:Adipocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D002454:Cell Differentiation; D002474:Cell-Free System / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D003470:Culture Media / Q000494:pharmacology; D016895:Culture Media, Serum-Free / Q000494:pharmacology; D007004:Hypoglycemic Agents / Q000494:pharmacology; D020287:In Situ Nick-End Labeling; D051034:Inhibitor of Apoptosis Proteins; D007328:Insulin / Q000494:pharmacology; D051379:Mice; D009419:Nerve Tissue Proteins / Q000096:biosynthesis* / Q000187:drug effects; D051616:Neuronal Apoptosis-Inhibitory Protein; D011506:Proteins / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D018160:Receptors, Cytoplasmic and Nuclear / Q000187:drug effects / Q000378:metabolism; D020123:Sirolimus / Q000494:pharmacology; D014157:Transcription Factors / Q000187:drug effects / Q000378:metabolism
D000900:Anti-Bacterial Agents; D003470:Culture Media; D016895:Culture Media, Serum-Free; D007004:Hypoglycemic Agents; D051034:Inhibitor of Apoptosis Proteins; D007328:Insulin; C496801:Naip1 protein, mouse; C496803:Naip6 protein, rat; D009419:Nerve Tissue Proteins; D051616:Neuronal Apoptosis-Inhibitory Protein; D011506:Proteins; D018160:Receptors, Cytoplasmic and Nuclear; D014157:Transcription Factors; D020123:Sirolimus