AIFM3 Has Pro-apoptotic, Whereas LZTR1 Has Bilateral Functions In The Intrinsic Apoptosis Pathway

Leucine Zipper-Like Post-Translational Regulator 1 (LZTR1) is associated with several congenital diseases and cancers. The degradation of LZTR1 upon apoptosis induction in HeLa cells was reported. In addition, mass spectrometry analyses indicate that LZTR1 interacts with Apoptosis Inducing Factor Mitochondria Associated 3 (AIFM3) protein in HEK293 cells. However, the functions of LZTR1 and AIFM3 in apoptosis are not known. In this study, the characterization of the roles of LZTR1 and AIFM3 in the intrinsic apoptosis mechanism was aimed. For this purpose, firstly, FLAG-LZTR1 and Myc-AIFM3 expression plasmids had been prepared and stably FLAG-LZTR1-expressing HEK293 Flp-In cells were established. Myc-AIFM3 expression plasmids were transiently transfected into parental and stably FLAG-LZTR1-expressing HEK293 cells. Apoptosis was triggered by treating cells with hydrogen peroxide (H2O2), and the levels of apoptosis-associated target proteins were analyzed using western blotting. Our analyses firstly revealed that H2O2 treatment triggered intrinsic apoptosis through p53/p21/BCL2/Caspase 8/Caspase 9/Caspase 3 axis of the intrinsic apoptosis pathway in HEK293 cells. In addition, increased cleaved Caspase 9, Caspase 3, and PARP1 protein levels were observed in AIFM3-overexpressing cells. LZTR1 was found to have pro-apoptotic roles by increasing AIFM3 and cleaved Caspase 3 proteins and anti-apoptotic roles by decreasing cleaved Caspase 8, Caspase 9, and PARP1 proteins. In conclusion, the data obtained in this study indicate that AIFM3 has pro-apoptotic, whereas LZTR1 has both anti- and pro-apoptotic roles in the intrinsic apoptosis pathway.