solute carrier family 22 member 1 (organic cation transporter 1, hOCT1, SLC22A1, OCT1)
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Function
- translocates a broad array of organic cations with various structures & molecular weights including
- model compounds 1-methyl-4-phenylpyridinium (MPP) tetraethylammonium (TEA) N-1-methylnicotinamide (NMN) 4-(4-(dimethylamino)styryl)-N-methylpyridinium (ASP)
- endogenous compounds choline, guanidine, histamine, epinephrine, adrenaline, noradrenaline & dopamine
- drugs quinine & metformin
- transport of organic cations is inhibited by a broad array of compounds including: tetramethylammonium (TMA), cocaine, lidocaine, NMDA receptor antagonists, atropine, prazosin, cimetidine, TEA & NMN, guanidine, cimetidine, choline, procainamide, quinine, tetrabutylammonium, & tetrapentylammonium
- translocation of organic cations is electrogenic & pH-independent
- translocates organic cations across the plasma membrane in both directions transports the polyamines spermine & spermidine
- transports pramipexole across the basolateral membrane of the proximal tubular epithelial cells
- choline transport is activated by MMTS
- regulated by intracellular signaling pathways including:
- inhibition by protein kinase A activation
- activation by the calmodulin, CAM kinase 2 & LCK
- phosphorylated (putative)
- KM=1.47 mM for metformin
- KM=229 uM for TEA
- KM=14.6 uM for MPP
- Vmax=396 pmol/min/mg enzyme for metformin uptake
- Vmax=2.89 nmol/min/mg enzyme for TEA uptake
Structure
- belongs to the major facilitator superfamily, organic cation transporter family
Compartment
Alternative splicing
named isoforms=4
Expression
- widely expressed with high level in liver
- isoform 1 & isoform 2 are expressed in liver
- isoforms 1-4 expressed in glial cell lines
- in the liver activated by HNF4A & suppressed by bile acids via NR0B2
- increased by cholesterol treatment in hepatocytes