AbstractTMEM45A has been discovered as an essential biomarker for chemoresistance induced by hypoxia in cancer cells. Indeed, when
TMEM45A expression is silenced, HepG2 hepatocarcinoma cells incubated with etoposide under hypoxia (1 % O2) are sensitive to cell death induced by etoposide.
Furthermore, Kaplan Meier curves show that TMEM45A can be used as a prognostic factor for cancer patients. However,TMEM45A function is still unknown. In order to discover the TMEM45A function, we used a split-ubiquitin yeast-two hybrid system to identify proteins that interact with TMEM45A. VKORC1 -Vitamin K
2,3 epoxide reductase complex subunit 1-was shown to interact with TMEM45A. This interaction was confirmed by co-immunofluorescence and co-immunoprecipitation. TMEM45A was evidenced to be involved in the resistance of cancer cells to etoposide and since TMEM45A interacts with VKORC1, we sought whether VKORC1 could also be implicated in this process. VKORC1 silencing using siRNA rendered HepG2 cells more sensitive to toposide under hypoxia as shown by caspase activity assays as well as by studying PARP cleavage.
In a second time, we generated knock-out mice for TMEM45A with the aim to analyze its function in vivo. We noticed that the knock-out mice are fertile, viable and have no obvious phenotype. As TMEM45A expression is high in the skin, we investigated the impact of the absence of TMEM45A in mice epidermis and in human reconstructed epidermis invalidated for TMEM45A. We were not able to evidence differences in the morphology, in the differentiation and in the epithelial barrier formation in the epidermis when TMEM45A was deleted.
Our results allow to define new perspectives about TMEM45A function. This protein could be for example in coagulation during wound healing of the epidermis.
|Date of Award||30 Sep 2015|
|Supervisor||Carine MICHIELS (Supervisor), Olivier De Backer (Co-Supervisor), Yves Poumay (President), Isabelle Hamer (Jury), Carlos GRAUX (Jury) & Thierry Magnaldo (Jury)|