solute carrier family 22 member 4 (SLC22A4, organic cation/carnitine transporter 1, ergothioneine transporter, ET transporter, ETT, OCTN1, UT2H)

Function

• Na+ dependent, low affinity carnitine transporter
• stoichiometry: 1 Na+ with 1 carnitine
• also transports organic cations such as tetraethylammonium (Na+ independent)
• ergothioneine appears to be a substrate
• interacts with PDZK1 (putative)

Kinetic parameters:

• KM=0.470 mM for TEA (37C & pH=7.4)
• Vmax=0.974 nmol/min/mg enzyme toward TEA (37C & pH=7.4)
• pH dependence:
• more active at neutral & alkaline pHs than at acidic pH

Structure

• belongs to the major facilitator superfamily, organic cation transporter family

Compartment

membrane

Expression

• widely expressed
• expressed in blood, bone marrow, trachea, fetal liver, intestinal epithelial cells > kidney, skeletal muscle, prostate, lung, pancreas, placenta, heart, uterus, spleen & spinal cord
• expressed in CD68 macrophage & CD43 T-cells but not in CD20 B-cells
• predominantly expressed in CD14 cells in peripheral blood mononuclear cells
• overexpressed upon TNF-alpha treatment

Pathology

• defects in SLC22A4 may be a cause of susceptibility to Crohn's disease; highly expressed in intestinal cell types affected by Crohn's disease, including epithelial cells
• defects in SLC22A4 may be a cause of rheumatoid arthritis

More general terms

• transmembrane 12 protein
• solute carrier family 22 (SLC22, SLC22A)
• major facilitator superfamily (MFS)
• glycoprotein

Additional terms

• inflammatory bowel disease

Database

• Kegg: http://www.genome.jp/dbget-bin/www_bget?hsa:6583
• OMIM: https://mirror.omim.org/entry/604190
• OMIM: https://mirror.omim.org/entry/266600
• UniProt: http://www.uniprot.org/uniprot/Q9H015.html