The Affection Of Atox1 On The Mitochondrial Function Of Pancreatic Cancer Cells And Its Mechanisms

Atoxl was first studied extensively as a copper molecular chaperone.Atoxl binds to Cu via two conserved Cys residues in a surface exposed MTCXXC(X,any residue)copper-binding motif,and Atoxl contains a distinct nuclear localization sequence(NLS)KKTGK at its C-terminal portion.The main function of Atoxl is to transport copper to ATP7A/B.This physiological process is essential for the cell to maintain copper homeostasis.Inactivation or deletion of Atoxl will result in immature copper-binding secretase(PAM,etc.).Most current studies on Atoxl are based on model of copper transfer to the Atoxl-ATP7A/B,including Menkes and Wilson disease,cisplatin resistance,neuronal differentiation and neointimal formation after vascular injury.In addition,it was further explored the regulation of Atoxl on cellular redox homeostasis.Subsequent studies of Atoxl demonstrated the important role of this small copper chaperone protein in regulating transcription as a transcription factor.The expression level of Atoxl in pancreatic cancer cells is high.Therefore,Atoxl was selected as the research object to explore its effect on pancreatic cancer cell proliferation and mitochondrial function.Copper(Cu)is an essential nutrient for organisms,and copper ions are essential cofactors in proteins involved in cellular responses such as respiratory processes,antioxidant defenses,pigment production,connective tissue and neurotransmitter biosynthesis.The redox ability of Cu(conversion between Cu+and Cu2+)makes the Cu-carrying protein play an important role as an electron carrier and a redox catalyst in the living system.In order to avoid the toxicity of Cu+,the concentration of Cu in the cell requires specific protein regulation,specific proteins promote its absorption,efflux and distribution to related Cu-dependent proteins and enzymes.There are four major modes of copper transport in human cells:copper enters the cytoplasm through the trimeric transmembrane protein Ctrl,Atoxl transports copper to the ATP7A and ATP7B transporters in the Golgi network,and Cox 17 delivers copper to the mitochondrial electron transport chain.Complex IV,CCS transports copper to superoxide dismutase(SOD1).Therefore,we can find that copper homeostasis is related to mitochondrial activity and Golgi network transport.In this study,over-inhibition or overexpression of Atoxl in pancreatic cancer cells revealed that inhibition of Atoxl can directly or indirectly affect cell proliferation by inhibiting the expression of mitochondrial inorganic pyrophosphatase2(PPA2)gene and thereby affecting mitochondrial function.When Overoxl is overexpressed,the level of mRNA of PPA2 is quantified and the level of cell proliferation is elevated.By constructing the dual luciferase vector and CHIP experiments,it was demonstrated that Atoxl as a transcription factor has the function of binding to the cis-elements in the PPA2 promoter,thereby affecting the expression of PPA2.In the inhibition of Atox1 in pancreatic cancer cells,overexpression of PPA2 partially restored mitochondrial function and cell proliferation.Therefore,when Atox1 acts as a transcription factor,it is activated by copper into the nucleus,which helps to affect mitochondrial function.The involvement of Atoxl as a transcription factor in other functions of cells remains to be further explored.