DEPTOR is a direct p53 target that suppresses cell growth and chemosensitivity

Abstract

DEP-domain containing mTOR-interacting protein (DEPTOR), a natural mTOR inhibitor, has essential roles in several processes, including cell growth, metabolism, apoptosis, and immunity. DEPTOR expression has been shown to be diversely controlled at transcriptional levels in cell- and context-specific manners. However, whether there is a general mechanism for the regulation of DEPTOR expression remains largely unknown. Here, we report that DEPTOR is a downstream target of the tumor suppressor, p53, whose activity is positively correlated with DEPTOR expression both in vitro in cell cultures and in vivo in mouse tissues. Mechanistically, p53 directly binds to the DEPTOR promoter and transactivates its expression. Depletion of the p53-binding site on the DEPTOR promoter by CRISPR-Cas9 technology decreases DEPTOR expression and promotes cell proliferation and survival by activating AKT signaling. Importantly, inhibition of AKT by small molecular inhibitors or genetic knockdown abrogates the induction of cell growth and survival induced by deletion of the p53-binding region on the DEPTOR promoter. Furthermore, p53, upon activation by the genotoxic agent doxorubicin, induces DEPTOR expression, leading to cancer cell resistance to doxorubicin. Together, DEPTOR is a direct p53 downstream target and contributes to p53-mediated inhibition of cell proliferation, survival, and chemosensitivity.

The Cross Talk Between p53 and mTOR Pathways in Response to Physiological and Genotoxic Stresses

“…Third, mTORC1 directly phosphorylates IRS1 at sites that inhibit its interaction with PI3K ( Tzatsos, 2009 ). Therefore, high levels of DEPTOR, a natural inhibitor of both mTORC1 and mTORC2, inhibit mTORC1 and activate mTORC2 by relieving the feedback inhibition from mTORC1 to IRS1/PI3K signaling ( Peterson et al, 2009 ; Zhao et al, 2011 ; Zhao and Sun, 2012 ; Cui et al, 2020a ) ( Figure 1 ).…”

“…Given that DEPTOR inhibits both mTORC1 and mTORC2, and there is a negative feedback from mTORC1 to IRS1/PI3K signaling, p53-mediated DEPTOR expression has distinct roles in regulating mTORC2 under non-stressed and genotoxic stress conditions. In non-stressed cells, p53-mediated DEPTOR expression inhibits mTORC2 activity, which is reflected by the decreased phosphorylation of AKT at Ser473; whereas, upon genotoxic treatment, the dramatic induction of DEPTOR expression via p53 hyperactivation inhibits mTORC1, subsequently alleviating the feedback inhibition from mTORC1 to IRS1, thereby activating mTORC2 via IRS1/PI3K signaling ( Cui et al, 2020a ) ( Figure 1 and Table 1 ).…”

Stabilization of DEPTOR sensitizes hypopharyngeal cancer to radiotherapy via targeting degradation

“…Quantitative real-time-PCR was performed using iTaq SYBR Green Mix (Bio-Rad) and the primers listed in Table S2 . 39 , 48 Each sample was examined at least in triplicate. PCR product specificity was confirmed by melting-curve analysis.…”

p53-mediated AKT and mTOR inhibition requires RFX7 and DDIT4 and depends on nutrient abundance

“…However, other reports indicate that p53 also can activate AKT [ 10 ] and does not affect AMPK [ 11 ]. p53 transcriptionally up-regulates multiple regulators of the PI3K-AKT-mTORC1 and AMPK-mTORC1 pathways, such as the PI3K opponent PTEN [ 8 ], the AKT inhibitors PHLDA3 and ASS1 [ 9 , 12 ], and the negative mTORC1 regulators AMPKβ [ 13 ], SESN1, SESN2 [ 6 ], and DEPTOR [ 14 ]. Consequently, the inhibition of mTORC1 activity is perceived to be critical for p53’s ability to regulate cell fitness [ 15 ] and to suppress tumorigenesis [ 16 – 18 ].…”

“…DDIT4 (also known as REDD1) is a p53 target [ 19 ] that has been shown to inhibit both AKT and mTORC1 [ 20 – 22 ]. While it has not been assessed whether p53-induced DDIT4, PTEN, AMPKβ, ASS1, and DEPTOR inhibit mTORC1 or AKT [ 8 , 12 – 14 , 19 ], knockdown of PHLDA3 has been shown to increase AKT activity irrespective of p53 [ 9 ]. The p53 targets SESN1 and SESN2 were essential for p53-mediated mTORC1 inhibition in MEF but only contributed to it in U2OS cells.…”