DIRAS3
GTP-binding protein Di-Ras3 precursor (Distinct subgroup of the Ras family member 3) (Rho-related GTP-binding protein RhoI) [ARHI] [NOEY2] [RHOI]
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Inhibition of Akt-mTOR signaling protects from obesity and extends life span in animals. In the present study, we analyse the impact of the small GTPase, GTP-binding RAS-like 3 (DIRAS3), a recently identified weight-loss target gene, on cellular senescence in adipose stromal/progenitor cells (ASCs) derived from human subcutaneous white adipose tissue (sWAT). We demonstrate that DIRAS3 knock-down (KD) in ASCs induces activation of Akt-mTOR signaling and proliferation arrest. DIRAS3 KD ASCs lose the potential to form colonies and are negative for Ki-67. Moreover, silencing of DIRAS3 results in a premature senescence phenotype. This is characterized by senescence-associated [i]β[/i]-galactosidase positive enlarged ASCs containing increased p16 level and activated retinoblastoma protein. DIRAS3 KD ASCs form senescence-associated heterochromatic foci as shown by increased level of γ-H2A.X positive foci. Furthermore, these cells express a senescence-associated secretory phenotype characterized by increased interleukin-8 secretion. Human DIRAS3 KD ASCs develop also a senescence phenotype in sWAT of SCID mice. Finally, we show that DIRAS3 KD in ASCs stimulates both adipogenic differentiation and premature senescence. In conclusion, our data suggest that silencing of DIRAS3 in ASCs and subsequently hyper-activation of Akt-mTOR drives adipogenesis and premature senescence. Moreover, differentiating ASCs and/or mature adipocytes may acquire features of cellular senescence.
MeSH Terms
- Adipocytes
- Adipogenesis
- Adipose Tissue, White
- Cell Proliferation
- Cellular Senescence
- Cyclin-Dependent Kinase Inhibitor p16
- Female
- Gene Silencing
- Humans
- Proto-Oncogene Proteins c-akt
- Signal Transduction
- Stem Cells
- TOR Serine-Threonine Kinases
- beta-Galactosidase
- rho GTP-Binding Proteins
Keywords
- DIRAS3
- adipocyte
- adipogenesis
- adipose stem cell
- adipose stromal/progenitor cell
- aging
- mTOR
- obesity
- senescence
Long-term weight-loss (WL) interventions reduce insulin serum levels, protect from obesity, and postpone age-associated diseases. The impact of long-term WL on adipose-derived stromal/progenitor cells (ASCs) is unknown. We identified DIRAS3 and IGF-1 as long-term WL target genes up-regulated in ASCs in subcutaneous white adipose tissue of formerly obese donors (WLDs). We show that DIRAS3 negatively regulates Akt, mTOR and ERK1/2 signaling in ASCs undergoing adipogenesis and acts as a negative regulator of this pathway and an activator of autophagy. Studying the IGF-1-DIRAS3 interaction in ASCs of WLDs, we demonstrate that IGF-1, although strongly up-regulated in these cells, hardly activates Akt, while ERK1/2 and S6K1 phosphorylation is activated by IGF-1. Overexpression of DIRAS3 in WLD ASCs completely inhibits Akt phosphorylation also in the presence of IGF-1. Phosphorylation of ERK1/2 and S6K1 is lesser reduced under these conditions. In conclusion, our key findings are that DIRAS3 down-regulates Akt-mTOR signaling in ASCs of WLDs. Moreover, DIRAS3 inhibits adipogenesis and activates autophagy in these cells.
MeSH Terms
- Adipogenesis
- Adult
- Animals
- Autophagy
- Cell Differentiation
- Cells, Cultured
- Female
- Gene Expression Regulation
- Humans
- Insulin-Like Growth Factor I
- MAP Kinase Signaling System
- Mice
- Middle Aged
- Phosphorylation
- Proto-Oncogene Proteins c-akt
- Stem Cells
- Subcutaneous Fat
- TOR Serine-Threonine Kinases
- Weight Loss
- Young Adult
- rho GTP-Binding Proteins
Keywords
- Adipogenesis
- Aging
- Akt
- Autophagy
- Caloric restriction
- DIRAS3
- ERK1/2
- Human adipose-derived stromal/progenitor cells
- IGF-1
- Insulin
- Obesity
- Weight loss
- mTOR