Role of Jab1/CSN5 in targeting immatur BCRP for endoplasimic reticulum-associated degration

Abstract

ABSTRACT

Role of Jab1/CSN5 in targeting immature BCRP for endoplasmic reticulum-associated degradation

Lee, Ji-Yoon Advisor: Prof. Yun Jisoo Department of Bio new drug development Graduate School of Chosun University

Breast cancer resistance protein (BCRP/ABCG2) is an ABC half-transporter, glycoprotein that confers resistance to anticancer drugs such as mitoxantrone, topotecan, and SN-38. BCRP is degraded in human cancer cells treated with glycosylation inhibitor, tunicamycin. In this study, I have attempted to elucidate the degradation mechanism of immature BCRP. The cellular interaction with Jab1/CSN5 was identified using the wild type, mutant (N596Q) of BCRP and Jab1/CSN5 after cotransfection of their expression plasmids to HEK293T cells. The cells were treated with the various inhibitors. In vitro binding assay, immunoprecipitation and Western blot analyses were performed to characterize the expression status of BCRP and interaction with Jab1/CSN5. I found that degradation of BCRP induced by tunicamycin is inhibited by proteasome inhibitor, MG132 and identified that Jab1/CSN5 acts as a binding partner of immature BCRP. In cotransfected HEK293T cells, mutant BCRP (N596Q) binds to Jab1/CSN5 under both the presence and the absence of proteasome inhibitors. These results demonstrate that Jab1/CSN5 especially binds to immature BCRP. In fact, endogenous Jab1/CSN5 interacts with immature BCRP induced by tunicamycin and MG132 in SK-MES-1 and MCF-7 cells. Deglycosylated immature BCRP is targeted to a proteasome-dependent degradation pathway. Jab1/CSN5 acts as mediator targeting immature BCRP to endoplasmic reticulum-associated degradation (ERAD) pathway and prompts subsequent degradation of immature BCRP by proteasome.