Tuberous sclerosis complex (TSC) is a human syndrome characterized by widespread development of benign tumors in a variety of organs including skin, brain, lung, heart and kidney. TSC is caused by mutation in either the TSC1 or TSC2 gene. Recent studies have indicated that TSC1 and TSC2 suppress the mammalian target of rapamycin (mTOR) signaling pathway to control cell growth;thus, abnormal activation of mTOR signaling as a result of mutation in TSC1 or TSC2 gene may underlie the pathogenesis of TSC. While mechanisms associated with mTOR regulation and with mTOR downstream effects have been partly characterized, much is still unknown regarding these mechanisms. Importantly, treatment of TSC is palliative and no effective cure is known. We have recently found that the IKK complex (key upstream regulator of the transcription factor NF-kB) interacts with the mTOR complex and significantly increases both mTORC1 and mTORC2 activity. Additionally, our results revealed that mTOR controls IKK/NF-NF-kB activation reciprocally. These results implicate IKK/NF- kappaB pathway as a novel regulator of TSC/mTOR signaling pathway. My data also demonstrate that both TSC2 and rapamycin regulate IKK/NF-kB activity through mTORC1 in an Akt-dependent manner. Based on my published studies and preliminary data, I hypothesize that IKK and NF-kB are critical regulators and effectors for mTOR and Akt in controlling the progression of TSC, and that rapamycin in combination with an IKK inhibitor could effectively block the activity of mTOR, Akt and IKK/NF-kB and ultimately block progression of TSC in TSC animal models. I will characterize the mechanism whereby IKK1 controls TORC1 and mTORC2 activity in several cancer cells and in TSC2 -/- MEF cells. I will extensively examine how TSC2 and rapamycin, in combination with an IKK inhibitor, affect NF-kB activity and TSC progression in cells and TSC animal models. The goal of this proposal is to achieve a mechanistic understanding of the interaction between IKK/NF-kB and mTOR pathways in promoting cell survival and growth, and progression of TSC. The proposed genetic and biochemical analyses and animal model studies will provide novel insight into the regulation and function of TSC/mTOR and IKK/NF-kB pathways, and the progression of TSC. Further studies could lead to the identification of new therapeutic targets and ultimately help develop rational, mechanism- based treatment strategies that target TSC and TSC-related tumors.
Tuberous Sclerosis Complex (TSC) is a human syndrome characterized by widespread development of benign tumors in multiple tissues, caused by the mutations in either TSC1 or TSC2 tumor suppressor genes and the subsequent abnormal activation of mTOR. So far, there is no effective cure for TSC although mTOR inhibitors, such as rapamycin, have shown some benefit in clinical trials. My published and preliminary studies indicated that IKK and the transcription factor NF-kB play critical roles in controlling the TSC2/mTOR signaling pathway. We hypothesize that genetic inhibition of IKK1 or combination inhibition of mTOR and IKK/NF- kB by IKK inhibitors and rapamycin will effectively block progression of TSC. Cell-based and animal model studies are proposed to test our hypothesis. The completion of the project could lead to the identification of new therapeutic targets and ultimately help develop rational mechanism-based treatment strategies that target TSC in a TSC clinical trial. Additionally, the studies will provide new insight into the control of both mTOR complexes (mTORC1 and mTORC2), with subsequent effects on key downstream regulators such as Akt.
|Dan, Han C; Ebbs, Aaron; Pasparakis, Manolis et al. (2014) Akt-dependent activation of mTORC1 complex involves phosphorylation of mTOR (mammalian target of rapamycin) by I?B kinase ? (IKK?). J Biol Chem 289:25227-40|