AJP - GI AJP: Lung Cellular and Molecular Physiology
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH
QUICK SEARCH:   [advanced]


     

Am J Physiol Gastrointest Liver Physiol (October 8, 2009). doi:10.1152/ajpgi.00177.2009
This Article
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Google Scholar
Right arrow Articles by Schonhoff, C. M.
Right arrow Articles by Anwer, M. S.
PubMed
Right arrow PubMed Citation
Right arrow Articles by Schonhoff, C. M.
Right arrow Articles by Anwer, M. S.

Research Article

PKC{varepsilon} DEPENDENT AND INDEPENDENT EFFECTS OF TAUROLITHOCHOLATE ON PI3K/PKB PATHWAY AND TAUROCHOLATE UPTAKE IN HUH-NTCP CELL LINE

Christopher M. Schonhoff,1 Ai Yamazaki,2 Simon Hohenester,3 Cynthia RL Webster,4 Bernard Bouscarel,5 and M. Sawkat Anwer6,*

1 2Tufts Univ. Cummings School of Vet. Med 3University of Munich Medical Center 4Tufts Cummings School of Veterinary Medicine 5The George Washington University 6Tufts Univ. School of Vet. Med.

Submitted 11 May 2009 ; revision received 5 October 2009 ; accepted in final form 5 October 2009

ABSTRACT

The cholestatic bile acid taurolithocholate (TLC) inhibits biliary secretion of organic anions and hepatic uptake of taurocholate (TC). TLC has been suggested to induce retrieval of Mrp2 from the canalicular membrane via the PI3K/PKB-dependent activation of nPKC{varepsilon} in rat hepatocytes. The aim of the present study was to determine whether TLC induced inhibition of TC uptake may also involve PI3K-dependent activation of PKC{varepsilon} in HuH7 cells stably transfected with human NTCP (HuH-NTCP cells). To avoid direct competition for uptake, cells were pretreated with TLC, washed and then incubated with 3H-TC to determine TC uptake. TLC produced time- and dose-dependent inhibition of TC uptake. TLC inhibited TC uptake competitively without affecting NTCP membrane translocation. A PI3K inhibitor failed to reverse TLC-induced TC uptake inhibition and TLC inhibited PKB phosphorylation. TLC did activate nPKC{varepsilon} as evidenced by increased membrane translocation and nPKC{varepsilon}-Ser729 phosphorylation. Overexpression of DN-nPKC{varepsilon} reversed TLC-induced inhibition of PKB phosphorylation, but not of TC uptake. Finally, cAMP prevented TLC-induced inhibition of TC uptake via the PI3K pathway, and the prevention is due to sum of cAMP-induced stimulation and TLC-induced inhibition of TC uptake. Taken together, these results suggest that TLC-induced inhibition of PKB, but not of TC uptake, is mediated via nPKC{varepsilon}. Activation of nPKC{varepsilon} and inhibition of TC uptake by TLC are not mediated via the PI3K/PKB pathway.

Taurolithocholate; Taurocholate uptake; inhibition kinetics; DN-nPKCepsilon


* Tufts Univ. School of Vet. Med. sawkat.anwer{at}tufts.edu






HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH
Visit Other APS Journals Online
Copyright © 1977 by the American Physiological Society.