TCTP Silencing and mTOR Signaling
Authors:
Waheed Akberzie, Shane Kennedy, Daniel TeranMentor:
Nitika Parmar, Associate Professor of Biology, California State University Channel IslandsTCTP (Translationally Controlled Tumor Protein) is a highly conserved protein that has been suggested as a tumor-associated antigen as shown by its deregulation in many different types of cancers. TCTP has been hypothesized to impact the mTOR pathway via its interaction with the small G-protein, Rheb. In this study we investigated a possible link between TCTP and mTOR signaling by gene silencing using RNA interference in a mammalian cell line model system. The effects were monitored via analysis of S6 phosphorylation via immunoblotting and cell viability using MTT proliferation assays respectively. We treated HEK293 cells with three different TCTP siRNAs in a dose-dependent manner and confirmed silencing by semi-quantitative RT-PCR. We observed that silencing of the endogenous TCTP gene was found to stimulate growth and enhance S6 phosphorylation, implying that TCTP is inhibitory to mTOR signaling. We also analyzed the impact of TCTP silencing on phosphorylation of S6 under starved and stimulated conditions. Under starved conditions silencing of TCTP displayed differential results for the three siRNAs. While two siRNA treatments did not show an increase in S6 phosphorylation following serum stimulation, one siRNA treatment did. These results suggest a deeper investigation of the silencing effects of TCTP.