Sodium / glucose cotransporter 1

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Sodium / glucose cotransporter 1
Properties of human protein
Mass / length primary structure 664 amino acids
Secondary to quaternary structure multipass (14 TMS) membrane protein
Identifier
Gene names SLC5A1 SGLT1
External IDs
Transporter classification
TCDB 2.A.21.3.1
designation Solute: Sodium Symporter (SSS)
Occurrence
Homology family SSS Symporter family
Parent taxon Creature

The sodium / glucose cotransporter 1 (SGLT1) ( gene : SLC5A1 ) is a protein in the cell membrane of mammals that transports certain monosaccharides and sodium ions into the cell by means of a symport . In humans, it is responsible for ensuring that glucose and galactose are absorbed by the body in the intestines. It is also formed in the kidneys, where it helps with the reabsorption of glucose and sodium. Mutations in the SLC5A1 gene can lead to a transport deficiency and this to the rare glucose / galactose malabsorption .

functionality

The transport equation is:

As with all carriers , the transport is basically reversible, but the low sodium concentration in the cell ensures that the symport is directed inwards. This is not the case if the ATP-dependent sodium-potassium antiporter fails.

The preferred solutes are glucose and galactose, that is, hexoses with a D configuration on the fifth carbon atom.

The production of the transporter molecule is ramped up in some cancer cells. There is evidence that SGLT1 plays a role in fighting off bacterial infections in the gut.

Glucose uptake in the small intestine

In the intestinal SGLT-1 is used for uptake of glucose in the mucosal cells in the apical cell membrane expressed . So glucose is transported against the gradient between cells and the intestinal lumen. Glucose is passively transported from the cell into the blood via GLUT-2 .

Glucose reabsorption in the kidney

SGLT-2, which is similar in structure and function to SGLT-1, is only expressed in the kidney. It is closer to the glomerulus , more precisely in the pars convoluta of the proximal tubule . In contrast to the SGLT-1, the Symport only requires one mol of sodium per one mol of solute. This means that the transport is cheaper for the sodium gradient, and it also has a higher transport capacity. However, only a 100-fold glucose gradient can be built up between tubule and blood. In the pars recta of the proximal tubule, the glucose concentration has already dropped sharply due to SGLT-2, and consequently the gradient to the blood becomes greater. Here the SGLT-1 is expressed, which can build up a 10,000-fold glucose gradient with two moles of sodium in the Symport. Thus, apart from pathologies such as diabetes , all glucose is reabsorbed from the urine.

regulation

The expression and activity of SGLT1 is dependent on mechanisms that are sensitive to the extracellular glucose content. Alternatively, the expression of SGLT1 can be boosted via the sweet receptor T1R3 and the G protein Gustducin .

literature

  • Georg Löffler, Petro Petrides, Peter Heinrich (Eds.): Biochemistry and Pathobiochemistry . 8th edition. Springer Medizin Verlag Heidelberg, Heidelberg 2006, ISBN 978-3-540-32680-9 . ; P. 905, p. 1069

Individual evidence

  1. ↑ UniProt P13866
  2. ↑ TCDB : 2.A.21
  3. ↑ Casneuf VF, Fonteyne P, Van Damme N, et al : Expression of SGLT1, Bcl-2 and p53 in primary pancreatic cancer related to survival . In: Cancer Invest. . 26, No. 8, October 2008, pp. 852-9. doi : 10.1080 / 07357900801956363 . PMID 18853313 .
  4. ↑ Palazzo M, Gariboldi S, Zanobbio L, et al : Sodium-dependent glucose transporter-1 as a novel immunological player in the intestinal mucosa . In: J. Immunol. . 181, No. 5, September 2008, pp. 3126-36. PMID 18713983 .
  5. ↑ Yu LC, Huang CY, Kuo WT, Sayer H, Turner JR, Buret AG: SGLT-1-mediated glucose uptake protects human intestinal epithelial cells against Giardia duodenalis-induced apoptosis . In: Int. J. Parasitol. . 38, No. 8-9, July 2008, pp. 923-34. doi : 10.1016 / j.ijpara.2007.12.004 . PMID 18281046 .
  6. ↑ Dyer J, Daly K, Salmon KS, et al : Intestinal glucose sensing and regulation of intestinal glucose absorption . In: Biochem. Soc. Trans. . 35, No. Pt 5, November 2007, pp. 1191-4. doi : 10.1042 / BST0351191 . PMID 17956309 .
  7. ↑ Margolskee RF, Dyer J, Kokrashvili Z, et al : T1R3 and gustducin in gut sense sugars to regulate expression of Na + -glucose cotransporter 1 . In: Proc. Natl. Acad. Sci. USA . 104, No. 38, September 2007, pp. 15075-80. doi : 10.1073 / pnas.0706678104 . PMID 17724332 . PMC 1986615 (free full text).

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