Silencing of the small GTPase DIRAS3 induces cellular senescence in human white adipose stromal/progenitor cells.
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-associatedβ-galactosidase positive enlarged ASCs containing increased p16INK4Alevel 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.
Division of Cell Metabolism and Differentiation Research, Institute for Biomedical Aging Research, University of Innsbruck, A-6020 Innsbruck, Austria.
Asim
A
Ejaz
Department of Plastic and Reconstructive Surgery, Innsbruck Medical University, A-6020 Innsbruck, Austria.
Monika
M
Mattesich
Division of Cell Metabolism and Differentiation Research, Institute for Biomedical Aging Research, University of Innsbruck, A-6020 Innsbruck, Austria.
Werner
W
Zwerschke
D017667:Adipocytes / Q000166:cytology* / Q000378:metabolism; D050156:Adipogenesis / Q000235:genetics; D052436:Adipose Tissue, White / Q000166:cytology* / Q000378:metabolism; D049109:Cell Proliferation / Q000235:genetics; D016922:Cellular Senescence / Q000235:genetics*; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000378:metabolism; D005260:Female; D020868:Gene Silencing; D006801:Humans; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics; D013234:Stem Cells / Q000166:cytology* / Q000378:metabolism; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism; D001616:beta-Galactosidase / Q000378:metabolism; D020741:rho GTP-Binding Proteins / Q000235:genetics* / Q000378:metabolism
D019941:Cyclin-Dependent Kinase Inhibitor p16; C117386:DIRAS3 protein, human; C546842:MTOR protein, human; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases; D001616:beta-Galactosidase; D020741:rho GTP-Binding Proteins
DIRAS3; adipocyte; adipogenesis; adipose stem cell; adipose stromal/progenitor cell; aging; mTOR; obesity; senescence