Biology:SLC22A5

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Short description: Protein-coding gene in the species Homo sapiens


A representation of the 3D structure of the protein myoglobin showing turquoise α-helices.
Generic protein structure example

SLC22A5 is a membrane transport protein associated with primary carnitine deficiency. This protein is involved in the active cellular uptake of carnitine. It acts a symporter, moving sodium ions and other organic cations across the membrane along with carnitine. Such polyspecific organic cation transporters in the liver, kidney, intestine, and other organs are critical for the elimination of many endogenous small organic cations as well as a wide array of drugs and environmental toxins.[1] Mutations in the SLC22A5 gene cause systemic primary carnitine deficiency, which can lead to heart failure.[2]

Structure

The SLC22A5 gene, containing 10 exons,[3] is located on the q arm of chromosome 5 in position 31.1 and spans 25,910 base pair.[1] The gene produces a 63 kDa protein composed of 557 amino acids.[4][5] The protein has 12 putative transmembrane domains, with a long extracellular loop of 107 amino acids between the first two transmembrane domains and an intracellular loop between the fourth and fifth transmembrane domains. This long extracellular loop has three potential sites for N-glycosylation, and the intracellular loop has an ATP/GTP binding motif. In putative intracellular domains, there are five potential sites for protein-kinase C-dependent phosphorylation and one for protein-kinase A-dependent phosphorylation.[6]

Function

The SLC22A5 gene codes for a plasma integral membrane protein which functions as both an organic cation transporter and a sodium-dependent high affinity carnitine transporter.[1] The encoded protein is involved in the active cellular uptake of carnitine, transporting one sodium ion with one molecule of carnitine. Organic cations transported by this protein include tetraethylammonium (TEA) without involvement of sodium. The relative uptake activity ratio of carnitine to TEA is 11.3.[7]

Clinical Significance

The main phenotypical effect of autosomal recessive mutations, either compound heterozygous or homozygous,[2] in the SLC22A5 gene is systemic primary carnitine deficiency,[3] characterized by impaired carnitine transport, urinary carnitine wasting, low serum carnitine levels, reduced intracellular carnitine accumulation, impaired beta oxidation, and cytosolic fatty acid accumulation.[2] Patients often display metabolic decompensation, hypoketotic hypoglycemia, hepatic encephalopathy, Reye syndrome, and sudden infant death in their first year, followed by the later onset of cardiomyopathy or skeletal myopathy, arrhythmias, muscle weakness, and heart failure in early childhood.[2][8][9] Patients may be asymptomatic, with about 70% of asymptomatic patients having a missense mutation or in-frame deletion; nonsense mutation frequency is increased in symptomatic patients.[10] The symptoms and outcome of the disease can be drastically improved by replacement therapy with L-carnitine.[11] The estimated incidence of primary carnitine deficiency in newborns is about 1 in 40,000.[12]

Interactions

SLC22A5 interacts with PDZK1.[7]

See also

References

  1. ↑ 1.0 1.1 1.2 "Entrez Gene: SLC22A5 solute carrier family 22 (organic cation transporter), member 5". https://www.ncbi.nlm.nih.gov/sites/entrez?Db=gene&Cmd=ShowDetailView&TermToSearch=6584. 
  2. ↑ 2.0 2.1 2.2 2.3 "Exome sequencing identifies primary carnitine deficiency in a family with cardiomyopathy and sudden death". European Journal of Human Genetics 25 (6): 783–787. June 2017. doi:10.1038/ejhg.2017.22. PMID 28295041. 
  3. ↑ 3.0 3.1 Online Mendelian Inheritance in Man, OMIM®. Johns Hopkins University, Baltimore, MD. MIM Number: {603377}: {04/29/2015}: . World Wide Web URL: https://omim.org/
  4. ↑ "Integration of cardiac proteome biology and medicine by a specialized knowledgebase". Circulation Research 113 (9): 1043–53. October 2013. doi:10.1161/CIRCRESAHA.113.301151. PMID 23965338. 
  5. ↑ "SLC22A5 - Solute carrier family 22 member 5". Cardiac Organellar Protein Atlas Knowledgebase (COPaKB). https://amino.heartproteome.org/web/protein/O76082. 
  6. ↑ "cDNA sequence, transport function, and genomic organization of human OCTN2, a new member of the organic cation transporter family". Biochemical and Biophysical Research Communications 246 (3): 589–95. May 1998. doi:10.1006/bbrc.1998.8669. PMID 9618255. 
  7. ↑ 7.0 7.1 "SLC22A5 - Solute carrier family 22 member 5 - Homo sapiens (Human) - SLC22A5 gene & protein" (in en). https://www.uniprot.org/uniprot/O76082. 
  8. ↑ "MRI findings in encephalopathy with primary carnitine deficiency: a case report". Journal of Neuroimaging 25 (2): 325–328. 2014-03-10. doi:10.1111/jon.12102. PMID 24612242. 
  9. ↑ "Primary carnitine deficiency and sudden death: in vivo evidence of myocardial lipid peroxidation and sulfonylation of sarcoendoplasmic reticulum calcium ATPase 2" (in en). Cardiology 120 (1): 52–8. 2011. doi:10.1159/000333127. PMID 22116472. 
  10. ↑ "SLC22A5 mutations in a patient with systemic primary carnitine deficiency: the first Korean case confirmed by biochemical and molecular investigation". Annals of Clinical and Laboratory Science 42 (4): 424–8. 2012. PMID 23090741. 
  11. ↑ "Primary carnitine deficiency dilated cardiomyopathy: 28 years follow-up". International Journal of Cardiology 162 (2): e34–5. January 2013. doi:10.1016/j.ijcard.2012.05.038. PMID 22658351. 
  12. ↑ "Genetic epidemiology of the carnitine transporter OCTN2 gene in a Japanese population and phenotypic characterization in Japanese pedigrees with primary systemic carnitine deficiency". Human Molecular Genetics 8 (12): 2247–54. November 1999. doi:10.1093/hmg/8.12.2247. PMID 10545605. 

Further reading

External links

This article incorporates text from the United States National Library of Medicine, which is in the public domain.



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