TDP-43Interaction With The Intracellular Domain Of Amyloid Precursor Protein Induces P53-associated Apoptosis

Objective:To investigate the interaction between TDP-43(TAR DNA-binding protein43)and the intracellular domain of Amyloid Precursor Protein (AICD)；To explore a novelfunction of TDP-43in Alzheimer’s disease (AD) pathology.Methods:Immunofluorescence staining was performed to detect the location of TDP-43andAICD, respectively, and whether they colocalize with each other in culturedHEK293/COS7cells.2.To investigate the interaction between TDP-43and APP,wetransfected APP-FLAG and TDP-43-V5into HEK293cells. Cell lysates weresubjected to co-immunoprecipitation (Co-IP). We examined the endogenous bindingbetween AICD and TDP-43by Co-IP with the lysates from C57BL/6J adult mice brain.Furthermore, to examine the function of TDP-43on the transcriptional activity ofAICD,, we transfected AICD-FLAG and TDP-43-V5into HEK293cells andperformed luciferase assay using an APP-Gal4luciferase reporter system.. AICD hasbeen reported to modulate the transcription of P53. Thus quantitative real-time PCR（qPCR）was performed to measure the binding of TDP43to AICD on thetranscription of P53. To examine the interaction of AICD and TDP-43on apoptosis,We performed Caspsase3staining and TUNEL assay on N2a cells transfected withAICD, TDP-43or AICD plus TDP-43.Results:Immunfluorescence staining showed that TDP-43was localized in the nucleus.AICD was detected in both the nucleus and the cytoplasm. We have shown acolocalization between TDP-43and AICD in the nucleus in cultured HEK293/COS7 cells.2. Coimmunoprecipitation in the lysates from transfected cells and C57BL/6Jadult mice brain indicated that TDP-43interacts with AICD.3. Luciferase assayshowed that TDP-43and Fe65played a convergent role in modulating thetransactivation of AICD. TDP-43, similar to AICD, could increase the mRNA level ofP53. Furthermore, TDP-43enhanced AICD-mediated P53transcription.4. Caspase3staining and TUNEL staining showed that both AICD and TDP-43played a role ininducing apoptosis. Moreover, TDP-43enhanced AICD-induced apoptosis in N2a cellsand COS7cells significantly.Conclusion:In summary, TDP-43colocalizes and interacts with AICD in the nucleus. TDP-43enhances the transctivation of AICD and AICD-mediates P53transcription. TDP-43thus enhances AICD-induced apoptosis. Therefore, our study has revealed a novel roleof TDP-43in the pathogenesis of AD, and raised an intriguing possibility that theatrophy in AD may be mediated by TDP-43through APP signaling.