CANCER CHARACTHERISTICS AND CELLULAR LOCALIZATION OF HUMAN TESTIS EXPRESSED 261  PROTEIN IN HEPATOCYTES

Human testis expressed 261 (TEX261) protein is predicted to be involved in essential cellular pathways such as proliferation, apoptosis, and COPII-mediated intracellular trafficking, yet has been scarcely researched in human cell models. Since TEX261 dysregulation has been observed in HCC, investigating the role of TEX261 in hepatocytes is essential. In this study we utilized molecular cloning and fluorescent protein tags to visualize the expression of TEX261 and associated proteins SAR1A and ALPL by confocal microscopy. We observed that TEX261 is closely associated with both proteins, indicating that TEX261 may be involved in ALPL packing into the COPII complex responsible for intracellular trafficking from the ER to the Golgi apparatus. We assessed TEX261 role in apoptosis by measuring caspase 3 activity and observed that TEX261 overexpression induced apoptosis at a similar rate as the positive control but did not significantly increase apoptosis compared to the negative control. We also recorded cell proliferation by overexpressing and silencing TEX261 in two cell lines. Our data showed that altered TEX261 expression did not impact Thle-2 proliferation, but TEX261 overexpression did significantly decrease proliferation in the HCC cell line Hep3B2.1-7. Overall, our results suggest that TEX261 does play a role in intracellular trafficking, apoptosis and proliferation, yet future studies need to be done to further define its role in cell regulatory mechanisms. Better control of the experimental error seems to be required to define the function of TEX261 in apoptosis.