equilibrative nucleoside transporter 4 (hENT4, solute carrier family 29 member 4, plasma membrane monoamine transporter, SLC29A4, ENT4, PMAT, PSEC0113)
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Function
- polyspecific organic cation transporter
- efficiently transports many organic cations such as monoamine neurotransmitters 1-methyl-4-phenylpyridinium & biogenic amines including serotonin, dopamine, norepinephrine & epinephrine
- may play a role in regulating central nervous system homeostasis of monoamine neurotransmitters
- may be involved in luminal transport of organic cations in the kidney
- seems to use luminal proton gradient to drive organic cation reabsorption
- does not seem to transport nucleoside & nucleoside analogs such as uridine, cytidine, thymidine, adenosine#, inosine, guanosine, & azidothymidine
# adenosine is transported[2] may play a role in the regulation of extracellular adenosine concentrations in cardiac tissues, in particular during ischemia[2]
Structure
- N-glycosylated
- belongs to the SLC29A transporter family
Compartment
- membrane (putative)
- located to the plasma membranes of ventricular myocytes & vascular endothelial cells
- targeted to the apical membranes of differentiated kidney epithelial cells
Alternative splicing
named isoforms=2
Expression
- expressed abundantly in the heart, in both cardiomyocytes & vascular endothelial cells (at protein level)
- highly espressed in brain, kidney & skeletal muscle
- in the brain expressed in cerebellum, cerebral cortex, medulla, occipital pole, frontal & temporal lobes putamen & in the spinal cord lower expression in liver, pancreas, & liver
- expressed in endometrial tissue, exclusively in the stroma
- expression is high in the proliferative phase, decreases during the secretory phase, & is no longer detectable in the menstrual phase