Protein kinase C regulates the internalization and function of the human organic anion transporting polypeptide 1A2.
OBJECTIVE
The human organic anion transporting polypeptide 1A2 (OATP1A2) is expressed in cells from several regions of the human body, including the kidney, cholangiocytes and the blood-brain barrier, and mediates the cellular flux of various anionic substances, including drugs in clinical use. Several related mammalian transporters have been shown to be subject to post-translational regulation, including kinase-induced internalization. In the present study the role of protein kinase C (PKC) in the regulation of OATP1A2 was investigated in an in vitro cell model.


METHODS
COS-7 cells in which OATP1A2 was overexpressed were treated with the PKC-specific activator (phorbol 12-myristate 13-acetate; PMA) and the PKC-specific inhibitor (Go6976). The impact of these treatments on the function and regulation of OATP1A2 was determined.


RESULTS
PKC activation decreased the transport function of OATP1A2 in a time- and concentration-dependent manner. PMA (0.1 µM) decreased the V(max) of oestrone-3-sulphate uptake and decreased the cell surface expression of OATP1A2 immunoreactive protein; these effects of PMA were prevented by the PKC specific inhibitor Go6976. In further studies, PMA treatment accelerated the internalization of OATP1A2 but did not affect its recycling. The disruption of clathrine-dependent endocytosis attenuated both the constitutive and PKC-modulated internalization of OATP1A2. In contrast, blocking the caveolin-dependent pathway was without effect.


CONCLUSIONS
PKC regulates the transport function of OATP1A2 by modulating protein internalization; this effect of PKC is mediated in part by clathrine-dependent pathways.
Pharmacogenomics and Drug Development Laboratory, Faculty of Pharmacy, The University of Sydney, Australia. fanfan.zhou@sydney.edu.au
Fanfan
F
Zhou
Andy C
AC
Lee
Katja
K
Krafczyk
Ling
L
Zhu
Michael
M
Murray
D000818:Animals; D019921:Biotinylation; D019556:COS Cells; D002227:Carbazoles / Q000378:metabolism / Q000494:pharmacology*; D002522:Chlorocebus aethiops; D004791:Enzyme Inhibitors / Q000378:metabolism / Q000494:pharmacology*; D005822:Genetic Vectors; D006801:Humans; D027361:Organic Anion Transporters / Q000378:metabolism*; D010587:Phagocytosis / Q000187:drug effects; D010957:Plasmids; D011493:Protein Kinase C / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*
D002227:Carbazoles; D004791:Enzyme Inhibitors; D027361:Organic Anion Transporters; C512988:SLCO1A2 protein, human; C081021:Go 6976; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate