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RIP1 activates PI3K-Akt via a dual mechanism involving NF-kappaB-mediated inhibition of the mTOR-S6K-IRS1 negative feedback loop and down-regulation of PTEN.

Abstract：

:Therapeutic inhibition of mammalian target of rapamycin (mTOR) in cancer is complicated by the existence of a negative feedback loop linking mTOR to the phosphatidylinositol 3-kinase (PI3K)-Akt pathway. Thus, mTOR inhibition by rapamycin or TSC1/2 results in increased PI3K-Akt activation. The death domain kinase receptor interacting protein 1 (RIP1) plays a key role in nuclear factor-kappaB (NF-kappaB) activation and also activates the PI3K-Akt pathway through unknown mechanisms. RIP1 has recently been found to be overexpressed in glioblastoma multiforme, the most common adult primary malignant brain tumor, but not in grade II to III glioma. Our data suggest that RIP1 activates PI3K-Akt using dual mechanisms by removing the two major brakes on PI3K-Akt activity. First, increased expression of RIP1 activates PI3K-Akt by interrupting the mTOR negative feedback loop. However, unlike other signals that regulate mTOR activity without affecting its level, RIP1 negatively regulates mTOR transcription via a NF-kappaB-dependent mechanism. The second mechanism used by RIP1 to activate PI3K-Akt is down-regulation of cellular PTEN levels, which appears to be independent of NF-kappaB activation. The clinical relevance of these findings is highlighted by the demonstration that RIP1 levels correlate with activation of Akt in glioblastoma multiforme. Thus, our study shows that RIP1 regulates key components of the PTEN-PI3K-Akt-mTOR pathway and elucidates a novel negative regulation of mTOR signaling at the transcriptional level by the NF-kappaB pathway. Our data suggest that the RIP1-NF-kappaB status of tumors may influence response to treatments targeting the PTEN-PI3K-mTOR signaling axis.

journal_name

Cancer Res

journal_title

Cancer research

authors

Park S,Zhao D,Hatanpaa KJ,Mickey BE,Saha D,Boothman DA,Story MD,Wong ET,Burma S,Georgescu MM,Rangnekar VM,Chauncey SS,Habib AA

doi

10.1158/0008-5472.CAN-09-0474

subject

Has Abstract

pub_date

2009-05-15 00:00:00

pages

4107-11

issue

eissn

0008-5472

issn

1538-7445

pii

0008-5472.CAN-09-0474

journal_volume

pub_type

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RIP1 activates PI3K-Akt via a dual mechanism involving NF-kappaB-mediated inhibition of the mTOR-S6K-IRS1 negative feedback loop and down-regulation of PTEN.