Transcortin

Transcortin, also known as corticosteroid-binding globulin (CBG) or serpin A6, is a protein produced in the liver in animals. In humans it is encoded by the SERPINA6 gene. It is an alpha-globulin.[5][6][7]

SERPINA6
Available structures
PDBOrtholog search: PDBe RCSB
Identifiers
AliasesSERPINA6, CBG, serpin family A member 6
External IDsOMIM: 122500 MGI: 88278 HomoloGene: 20417 GeneCards: SERPINA6
Gene location (Human)
Chr.Chromosome 14 (human)[1]
Band14q32.13Start94,304,248 bp[1]
End94,323,389 bp[1]
RNA expression pattern
More reference expression data
Orthologs
SpeciesHumanMouse
Entrez

866

12401

Ensembl

ENSG00000277405
ENSG00000170099

ENSMUSG00000060807

UniProt

P08185

Q06770

RefSeq (mRNA)

NM_001756

NM_007618

RefSeq (protein)

NP_001747

NP_031644

Location (UCSC)Chr 14: 94.3 – 94.32 MbChr 12: 103.65 – 103.66 Mb
PubMed search[3][4]
Wikidata
View/Edit HumanView/Edit Mouse

Function

This gene encodes an alpha-globulin protein with corticosteroid-binding properties. This is the major transport protein for glucocorticoids and progestins in the blood of most vertebrates. The gene localizes to a chromosomal region containing several closely related serine protease inhibitors (serpins) which have evolved by duplication events.[7]

Binding

Transcortin binds several steroid hormones at high rates:

  • Cortisol - Approximately 75% of the cortisol in circulation is bound to transcortin. (The rest is bound to serum albumin.) Cortisol is thought to be biologically active only when it is not bound to transcortin.
  • Cortisone[8]
  • Deoxycorticosterone (DOC)[8]
  • Corticosterone - About 78% of serum corticosterone is bound to transcortin.
  • Aldosterone - Approximately 17% of serum aldosterone is bound to transcortin, while another 47% is bound to serum albumin. The remaining 36% is free.[9]
  • Progesterone - Approximately 18% of serum progesterone is bound to transcortin, while another 80% of it is bound to serum albumin. The remaining 2% is free.[10]
  • 17α-Hydroxyprogesterone[8]

In addition, approximately 4% of serum testosterone is bound to transcortin.[11] A similarly small fraction of serum estradiol is bound to transcortin as well.

Synthesis

Transcortin is produced by the liver and is increased by estrogens.[12]

Clinical significance

Mutations in this gene are rare. Only four mutations have been described, often in association with fatigue and chronic pain.[13] This mechanism for these symptoms is not known. This condition must be distinguished from secondary hypocortisolism. Exogenous hydrocortisone does not appear to improve the fatigue.

Hepatic synthesis of corticosteroid-binding globulin more than doubles in pregnancy; that is, bound plasma cortisol in term pregnancy is approximately 2 to 3 times that of nonpregnant women.[14][15]

See also

References
  1. ENSG00000170099 GRCh38: Ensembl release 89: ENSG00000277405, ENSG00000170099 - Ensembl, May 2017
  2. GRCm38: Ensembl release 89: ENSMUSG00000060807 - Ensembl, May 2017
  3. "Human PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
  4. "Mouse PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
  5. Hammond GL, Smith CL, Goping IS, Underhill DA, Harley MJ, Reventos J, Musto NA, Gunsalus GL, Bardin CW (August 1987). "Primary structure of human corticosteroid binding globulin, deduced from hepatic and pulmonary cDNAs, exhibits homology with serine protease inhibitors". Proc Natl Acad Sci U S A. 84 (15): 5153–7. Bibcode:1987PNAS...84.5153H. doi:10.1073/pnas.84.15.5153. PMC 298812. PMID 3299377.
  6. Byth BC, Billingsley GD, Cox DW (July 1994). "Physical and genetic mapping of the serpin gene cluster at 14q32.1: allelic association and a unique haplotype associated with alpha 1-antitrypsin deficiency". Am J Hum Genet. 55 (1): 126–33. PMC 1918218. PMID 7912884.
  7. "Entrez Gene: SERPINA6 serpin peptidase inhibitor, clade A (alpha-1 antiproteinase, antitrypsin), member 6".
  8. E. Edward Bittar; Neville Bittar (1997). Molecular and Cellular Endocrinology. Elsevier. p. 238. ISBN 978-1-55938-815-3. Retrieved 23 August 2012.
  9. Principles and Practice of Endocrinology and Metabolism. Lippincott Williams & Wilkins. 24 April 2001. p. 712. ISBN 978-0-7817-1750-2. Retrieved 23 August 2012.
  10. Negi (2009). Introduction To Endocrinology. PHI Learning Pvt. Ltd. p. 268. ISBN 978-81-203-3850-0. Retrieved 23 August 2012.
  11. Dunn JF, Nisula BC, Rodbard D (July 1981). "Transport of steroid hormones: binding of 21 endogenous steroids to both testosterone-binding globulin and corticosteroid-binding globulin in human plasma". The Journal of Clinical Endocrinology and Metabolism. 53 (1): 58–68. doi:10.1210/jcem-53-1-58. PMID 7195404.
  12. Musa BU, Seal US, Doe RP (September 1965). "Elevation of certain plasma proteins in man following estrogen administration: a dose-response relationship". J. Clin. Endocrinol. Metab. 25 (9): 1163–6. doi:10.1210/jcem-25-9-1163. PMID 4284083.
  13. Torpy DJ, Lundgren BA, Ho JT, Lewis JG, Scott HS, Mericq V (January 2012). "CBG Santiago: a novel CBG mutation". J. Clin. Endocrinol. Metab. 97 (1): E151–5. doi:10.1210/jc.2011-2022. PMID 22013108.
  14. Rosen MI, Shnider SM, Levinson G, Hughes (2002). Shnider and Levinson's anesthesia for obstetrics. Hagerstwon, MD: Lippincott Williams & Wilkins. p. 13. ISBN 0-683-30665-0.CS1 maint: multiple names: authors list (link)
  15. Ann M. Gronowski (6 May 2004). Handbook of Clinical Laboratory Testing During Pregnancy. Springer Science & Business Media. pp. 408–. ISBN 978-1-59259-787-1.

Further reading

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