The Degradation Mechanism Of P-glycoprotein In The Nerve Cells And Its Clinical Significance

P-glycoprotein (P-gp) is the most important and widely studied members of ABC(ATP Binding Cassette) super family. P-glycoprotein detoxifies cells by exportinghundreds of chemically unrelated toxins but has been implicated in multidrug resistance(MDR) in the treatment of cancers and the occurrence of intractable epilepsy. Cancer isaffected with proto-oncogene, anti-oncogene, apoptosis-related gene and repair gene.Whereas the P-glycoprotein plays an essential role in intractable epilepsy.Currently, theresearch about the mechanism of increased P-glycoprotein only from synthetic of theprotein. Due to the dynamic balance of P-glycoprotein in the synthesis and degradation, itis a new insight to research on the increased P-glycoprotein in intractable epilepsy fromthe perspective of protein degradation.ObjectiveIn the present study, we investigated the degradation pathway of P-glycoprotein inthe astrocytes and its mechanism in intractable epilepsy.Methods1.The ABCB1gene was transfected into U251cells, accompanied with the adenovirusas a vector, to establish a cell model with high expression of P-glycoprotein.2.Treat the cell models with specific proteasome inhibitor(MG132), lysosomalinhibitors(ChlQ) in different concentration for24hours. Detection the expression ofP-glycoprotein by immunoprecipitation and western blot to demonstrate whether thedegradation of P-glycoprotein in nerve cells is through ubiquitin proteasome pathway orlysosomal pathway.Results1.The expressions of P-glycoprotein significantly increased in specific proteasomeinhibitor(MG132) group compared with the control. And the expression of P-glycoproteinincreased with increasing MG132concentration，while the expressions of P-glycoproteindoes not increased with prolonging the drug treatment. 2.The expressions of P-glycoprotein has no significant difference among thelysosomal inhibitors(ChlQ) groups.Conclusion1.The degradation of P-glycoprotein in nerve cells is not through lysosomal pathway.2.The degradation of P-glycoprotein in nerve cells is through ubiquitin proteasomepathway.3.The inhibition of the ubiquitin proteasome can increase the expression ofubiquitinated P-glycoprotein in nerve cells, accompany with accumulation ofP-glycoprotein.