Studies On The Role And Molecular Mechanism Of Deubiquitinase USP14 In The Degradation Of Glutaminase C

GAC(glutaminase C)is a kidney-type glutaminase,which catalyzes the hydrolysis of glutamine to glutamate and ammonia.It participates in citric acid cycle and play important role in energy metabolism.Some recent findings reported that GAC promoted the occurence and development of many types of cancer,such as breast cancer and lung cancer.However the upstream regulation signaling pathway remains unclear.In our previous study,we found that USP14(ubiquitin specific peptidase 14)may bind to GAC in yeast two-hybrid assay.Therefore,we want to reveal the mode of action between USP14 and GAC,and its regulatory pathway in this work.We confirmed the binding between USP14 and GAC by immunoprecipitation.The knocking down of USP14 by si RNA increased GAC protein expression,but had no effect on its m RNA level.Due to the deubiquitinating activity of USP14,we tested the ubiquitination level of GAC after the knocking down or overexpression of USP14.The result proved that USP14 modulated the ubiquitination level of GAC obviously.The knocking down of USP14 increased the Lys48 type of ubiquitin chain on GAC,but the dead mutant USP14 had no such function.We conclude that USP14 promotes the degradation of GAC through the 26 S proteasome pathway,and the degradation of GAC may depend on the modification of the Lys48 type of ubiquitin chain.Finally,we examined the effects of USP14's deletion on the phenotype of non-small cell lung cancer cells.The results show that the deletion of USP14 can inhibit the proliferation of non-small-cell lung cancer cells,attenuate their ability to form colony,hinder cell cycle and autophagy.All these results indicate that USP14 plays an important role in the growth of non-small-cell lung cancer.