Calpain system regulates the differentiation of adult primitive mesenchymal ST-13 adipocytes.
The activity of calpain, a calcium-activated protease, is required during the mitotic clonal expansion phase of 3T3-L1 embryonic preadipocyte differentiation. Here we examined the role of calpain in the adipogenesis of ST-13 preadipocytes established from adult primitive mesenchymal cells, which do not require mitotic clonal expansion. After exposure to the calpain inhibitor, N-benzyloxycarbonyl-L-leucyl-L-leucinal or overexpression of calpastatin, a specific endogenous inhibitor of calpain, ST-13 preadipocytes acquired the adipocyte phenotype. Overexpression of calpastatin in ST-13 adipocytes stimulated the expression of adipocyte-specific CCAAT/enhancer-binding protein-alpha (C/EBPalpha), peroxisome proliferator-activated receptor (PPAR)-gamma, sterol regulatory element-binding protein 1, and the insulin signaling molecules, insulin receptor alpha, insulin-receptor substrates, and GLUT4. However, insulin-stimulated glucose uptake was reduced by approximately 52%. The addition of calpain to the nuclear fraction of ST-13 adipocytes resulted in the Ca(2+)-dependent degradation of PPARgamma and C/EBPalpha but not sterol regulatory element-binding protein 1. Exposing ST-13 adipocytes to A23187 also led to losses of endogenous PPARgamma and C/EBPalpha. Under both conditions, calpain inhibitors almost completely prevented C/EBPalpha cleavage but partially blocked the decrease of PPARgamma. Two ubiquitous forms of calpain, mu- and m-calpain, localized to the cytosol and the nucleus, whereas the activated form of mu- but not m-calpain was found in the nucleus. Finally, stable dominant-negative mu-calpain transfectants showed accelerated adipogenesis and increase in the levels of PPARgamma and C/EBPalpha during adipocyte program. These results support evidence that the calpain system is involved in regulating the differentiation of adult primitive mesenchymal ST-13 preadipocytes.
Yajima
Yukiko
Y
Tokyo Metropolitan Institute of Medical Science, 18-22 Honkomagome 3-chome, Tokyo 113-8613, Japan. yajima@rinshoken.or.jp
Sato
Mayumi
M
Sorimachi
Hiroyuki
H
Inomata
Mitsushi
M
Maki
Masatoshi
M
Kawashima
Seiichi
S
D017667:Adipocytes / Q000502:physiology*; D000273:Adipose Tissue / Q000254:growth & development; D000963:Antimetabolites / Q000378:metabolism; D015152:Blotting, Northern; D022763:CCAAT-Enhancer-Binding Protein-alpha / Q000037:antagonists & inhibitors; D000001:Calcimycin / Q000494:pharmacology; D002135:Calcium-Binding Proteins / Q000096:biosynthesis; D002154:Calpain / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000502:physiology*; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology*; D018076:DNA, Complementary / Q000096:biosynthesis / Q000235:genetics; D003847:Deoxyglucose / Q000378:metabolism; D004151:Dipeptides / Q000494:pharmacology; D006801:Humans; D013234:Stem Cells / Q000187:drug effects; D051780:Sterol Regulatory Element Binding Protein 1 / Q000096:biosynthesis / Q000502:physiology; D013347:Subcellular Fractions / Q000502:physiology
D000963:Antimetabolites; D022763:CCAAT-Enhancer-Binding Protein-alpha; D002135:Calcium-Binding Proteins; D018076:DNA, Complementary; D004151:Dipeptides; D051780:Sterol Regulatory Element Binding Protein 1; C400241:benzyloxycarbonylleucyl-leucine aldehyde; D000001:Calcimycin; C033668:calpastatin; D003847:Deoxyglucose; D002154:Calpain; C449000:m-calpain; C449002:mu-calpain