Membrane localization of the electrogenic cation transporter rOCT1 in rat liver.
The polyspecific cation transporter rOCT1 in the rat was the first identified member of a new protein family with 12 presumed membrane-spanning alpha-helices and two large hydrophilic loops. Previous studies showed that rOCT1 is mainly expressed in liver and mediates electrogenic uptake of small organic cations into cells. Antibodies against partial sequences of rOCT1 were raised and their specificity was verified. Immunohistochemistry with rat liver and Western blots with isolated membranes showed that rOCT1 is localized within sinusoidal membranes of hepatocytes. Antibody reactions were also performed with intact and permeabilized human embryonic kidney cells that were stably transfected with rOCT1. They showed that the large hydrophilic loop after the first alpha-helix of rOCT1 is located extracellularly, while the C-terminus is located intracellularly. Translational regulation is suggested since the message of rOCT1 was distributed throughout the liver lobuli, whereas rOCT1 protein was observed only in hepatocytes surrounding the central veins.
Anatomisches Institut, Bayerischen Julius-Maximilians-Universität, Würzburg, Germany.
F
F
Meyer-Wentrup
U
U
Karbach
V
V
Gorboulev
P
P
Arndt
H
H
Koepsell
D000818:Animals; D015153:Blotting, Western; D002352:Carrier Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism / Q000648:ultrastructure; D003001:Cloning, Molecular; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008099:Liver / Q000166:cytology / Q000378:metabolism*; D008565:Membrane Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000502:physiology*; D009865:Oocytes / Q000502:physiology; D027701:Organic Cation Transport Proteins; D027702:Organic Cation Transporter 1; D000075102:Organic Cation Transporter 2; D016133:Polymerase Chain Reaction; D017433:Protein Structure, Secondary; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D011994:Recombinant Proteins / Q000096:biosynthesis; D014158:Transcription, Genetic; D014982:Xenopus laevis
D002352:Carrier Proteins; D008565:Membrane Proteins; D027701:Organic Cation Transport Proteins; D027702:Organic Cation Transporter 1; D000075102:Organic Cation Transporter 2; D012333:RNA, Messenger; D011994:Recombinant Proteins; C491013:SLC22A2 protein, human; C100590:Slc22a2 protein, rat