PMID- 16952420
OWN - NLM
STAT- MEDLINE
DCOM- 20070213
LR  - 20211203
IS  - 0006-3002 (Print)
IS  - 0006-3002 (Linking)
VI  - 1770
IP  - 1
DP  - 2007 Jan
TI  - Effects of rapamycin on cell proliferation and phosphorylation of mTOR and 
      p70(S6K) in HepG2 and HepG2 cells overexpressing constitutively active Akt/PKB.
PG  - 71-8
AB  - Mammalian target of rapamycin (mTOR) is a serine-threonine kinase that plays an 
      important role in the regulation of cell proliferation and protein synthesis 
      through the activation of its downstream target ribosomal p70 S6 kinase 
      (p70(S6K)). The levels of p-mTOR are regulated by the protein kinase B (Akt/PKB). 
      Therefore, the effects of insulin and rapamycin (an inhibitor of mTOR) on the 
      phosphorylation of mTOR (Ser 2448) and p70(S6K) (Thr 389) as well as on cell 
      proliferation in parental HepG2 cells and HepG2 cells overexpressing 
      constitutively active Akt/PKB (HepG2-CA-Akt/PKB) were studied. Insulin increased 
      the levels of phosphorylated mTOR and p70(S6K) in both the cell lines. Rapamycin 
      treatment partially decreased the phosphorylation of mTOR but completely 
      abolished the phosphorylation of p70(S6K) in the absence as well as presence of 
      insulin in both cell lines. The effect of insulin and rapamycin on the cell 
      proliferation in both cell lines was further studied. In the presence of serum, 
      parental HepG2 cells and HepG2-CA-Akt/PKB showed an increase in cell 
      proliferation until 120 and 168 h respectively. Rapamycin inhibited cell 
      proliferation under all experimental conditions more evident under serum deprived 
      conditions. Parental HepG2 cells showed decline in the cell proliferation after 
      48 h and the presence of insulin prolonged cell survival until 120 h and this 
      effect were also inhibited by rapamycin under serum deprived conditions. On the 
      contrary, HepG2-CA-Akt/PKB cells continued proliferation until 192 h. The effects 
      of insulin on cell proliferation were more pronounced in parental HepG2 cells as 
      compared to HepG2-CA-Akt/PKB cells. Long term effects of rapamcyin significantly 
      decreased the levels of p-mTOR (Ser 2448) both in the presence and absence of 
      insulin in these cells. A positive correlation between the levels of p-mTOR 
      (Ser2448) and cell proliferation was observed (99% confidence interval, 
      r(2)=0.525, p<0.0001). These results suggest that rapamycin causes a decline in 
      the cell growth through the inhibition of mTOR.
FAU - Varma, Shailly
AU  - Varma S
AD  - Department of Biochemistry, College of Medicine, 107 Wiggins Road, University of 
      Saskatchewan, Saskatoon, SK, Canada S7N5E5.
FAU - Khandelwal, Ramji L
AU  - Khandelwal RL
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
DEP - 20060801
PL  - Netherlands
TA  - Biochim Biophys Acta
JT  - Biochimica et biophysica acta
JID - 0217513
RN  - EC 2.7.- (Protein Kinases)
RN  - EC 2.7.1.1 (MTOR protein, human)
RN  - EC 2.7.11.1 (Proto-Oncogene Proteins c-akt)
RN  - EC 2.7.11.1 (Ribosomal Protein S6 Kinases, 70-kDa)
RN  - EC 2.7.11.1 (TOR Serine-Threonine Kinases)
RN  - W36ZG6FT64 (Sirolimus)
SB  - IM
MH  - Cell Line
MH  - Cell Proliferation/*drug effects
MH  - Fluorescent Antibody Technique
MH  - Humans
MH  - Phosphorylation
MH  - Protein Kinases/*metabolism
MH  - Proto-Oncogene Proteins c-akt/*metabolism
MH  - Ribosomal Protein S6 Kinases, 70-kDa/*metabolism
MH  - Sirolimus/*pharmacology
MH  - TOR Serine-Threonine Kinases
EDAT- 2006/09/06 09:00
MHDA- 2007/02/14 09:00
CRDT- 2006/09/06 09:00
PHST- 2006/04/12 00:00 [received]
PHST- 2006/06/22 00:00 [revised]
PHST- 2006/07/19 00:00 [accepted]
PHST- 2006/09/06 09:00 [pubmed]
PHST- 2007/02/14 09:00 [medline]
PHST- 2006/09/06 09:00 [entrez]
AID - S0304-4165(06)00206-6 [pii]
AID - 10.1016/j.bbagen.2006.07.016 [doi]
PST - ppublish
SO  - Biochim Biophys Acta. 2007 Jan;1770(1):71-8. doi: 10.1016/j.bbagen.2006.07.016. 
      Epub 2006 Aug 1.