TERT Promotes Cellular and Organismal Survival Independently of Telomerase Activity

The expression level of the telomerase catalytic subunit (telomerase reverse transcriptase, TERT) positively correlates with cell survival after exposure to several lethal stresses. However, whether the protective role of TERT is independent of telomerase activity has not yet been clearly explored. Here, we genetically evaluated the protective roles of both TERT and telomerase activity against cell death induced by staurosporine (STS) and N-methyl-D-aspartic acid (NMDA). First generation (G1) TERT-deficient mouse embryonic fibroblasts (MEFs) displayed an increased sensitivity to STS, while TERT transgenic MEFs were more resistant to STS-induced apoptosis than wild-type. Deletion of the telomerase RNA component (TERC) failed to alter the sensitivity of TERT transgenic MEFs to STS treatment. Similarly, NMDA-induced excitotoxic cell death of primary neurons was suppressed by TERT, but not by TERC both in vitro and in vivo. Specifically, NMDA accelerated death of TERT-deficient mice, while TERT transgenic mice showed enhanced survival when compared with wild-type littermates after administration of NMDA. In addition, the transgenic expression of TERT protected motor neurons from apoptosis induced by sciatic nerve axotomy. These results indicate that telomerase activity is not essential for the protective function of TERT. This telomerase activity-independent TERT function may contribute to cancer development and aging independently of telomere lengthening.