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Am J Physiol Gastrointest Liver Physiol (September 11, 2008). doi:10.1152/ajpgi.90404.2008
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Submitted on June 30, 2008
Revised on August 18, 2008
Accepted on September 9, 2008

Canalicular Mrp2 localization is reversibly regulated by the intracellular redox status

Shuichi Sekine1, Kousei Ito2, and Toshiharu Horie3*

1 Graduate school of Pharmaceutical Sciences, Chiba University
2 The University of Tokyo Hospital
3 Chiba University, Japan

* To whom correspondence should be addressed. E-mail: horieto{at}p.chiba-u.ac.jp.

Oxidative stress is known to be a common feature of cholestatic syndrome. We have described the internalization of multidrug resistance-associated protein 2 (Mrp2), a biliary transporter involved in bile-salt independent bile flow, under acute oxidative stress and a series of signaling pathways finally leading to the activation of novel protein kinase C (nPKC) were involved in this mechanism; however, it has been unclear whether the internalized Mrp2 localization was re-localized to the canalicular membrane when the intracellular redox status was recovered from oxidative stress. In this study, we demonstrated that decreased canalicular expression of Mrp2 induced by tertiary-butyl hydroperoxide (t-BHP) was recovered to the canalicular membrane by the replenishment of GSH by GSH-ethyl ester, a cell-permeable form of GSH. Moreover, pretreatment of isolated rat hepatocytes with colchicine and protein kinase A (PKA) inhibitor did not affect the t-BHP induced Mrp2 internalization process, but did prevent the Mrp2 recycling process induced by GSH replenishment. Moreover, intracellular cAMP concentration similarly changed with the change of intracellular GSH content. Taken together, our data clearly indicate that the redox-sensitive balance of PKA/PKC activation regulates the reversible Mrp2 localization in two different pathways, the microtubule-independent internalization pathway and -dependent recycling pathway of Mrp2.




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Putative role for actin organization status in the dynamic localization of canalicular carriers under oxidative stress conditions
Am J Physiol Gastrointest Liver Physiol, April 1, 2009; 296(4): G969 - G969.
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