Senescence marker protein-30 regulates Akt activity and contributes to cell survival in Hep G2 cells.
Senescence marker protein-30 (SMP30) is highly expressed in cytosol of hepatocytes, and its amount decreases with aging. Human hepatocellular carcinoma cell line was transfected with pcDNA3/SMP30 (SMP30 transfectants), or as a control with pcDNA3 (mock transfectants). When cells were exposed to 20 ng/ml tumor necrosis factor-alpha (TNF-alpha) plus 10 ng/ml actinomycin D (Act-D) for 15 h, the viability of cells was decreased in both SMP30 and mock transfectants. However, the viability of cells was threefold higher in SMP30 transfectants than mock transfectants. Cell death was confirmed as apoptosis by TUNEL assay. The presence of trifluoperazine, a calmodulin (CaM) inhibitor, attenuated anti-apoptotic effect of SMP30 in both transfectants, but the effect was more prominent in SMP30 transfectants. Western blot analyses revealed that Akt, which acts as a survival factor in cells, was activated in SMP30, but not mock, transfectants either in the presence or absence of TNF-alpha plus Act-D. Further, trifluoperazine inhibited Akt activation in SMP30 transfectants. We therefore propose that interplay between CaM and SMP30 regulates Akt activity, and thus SMP30 acts as a survival factor in hepatocytes.
Matsuyama
Syujirou
S
Department of Gastroenterology, Juntendo University School of Medicine, Tokyo, Japan.
Kitamura
Tsuneo
T
Enomoto
Nobuyuki
N
Fujita
Toshiko
T
Ishigami
Akihito
A
Handa
Setsuko
S
Maruyama
Naoki
N
Zheng
Dongmei
D
Ikejima
Kenichi
K
Takei
Yoshiyuki
Y
Sato
Nobuhiro
N
D002135:Calcium-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D016895:Culture Media, Serum-Free / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D005786:Gene Expression Regulation; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008099:Liver / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D010768:Phosphoserine / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D015238:Sulfotransferases; D014162:Transfection; D014268:Trifluoperazine / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D002135:Calcium-Binding Proteins; D016895:Culture Media, Serum-Free; D047908:Intracellular Signaling Peptides and Proteins; D011518:Proto-Oncogene Proteins; C513323:RGN protein, human; D014409:Tumor Necrosis Factor-alpha; D010768:Phosphoserine; D003609:Dactinomycin; D014268:Trifluoperazine; C494918:AKT1 protein, human; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D015238:Sulfotransferases; C028152:alcohol sulfotransferase