GLUT-4

OMIM: 138 190
UniProt: P14672

GLUT -4 ( glucose transporter type 4) ( gene: SLC2A4 ) is a protein that is localized particularly in vesicles in mammalian cells. With GLUT-4 is a membrane transport protein. In humans is GLUT-4 is expressed in striated muscle and fat cells. One of the consequences of docking of insulin to the insulin receptor that combine the GLUT -4- vesicles with the cell membrane and thus the introduction of glucose into the cell is stimulated. Mutations in the GLUT4 gene can cause GLUT -4 deficiency and this mellitus to a ( rare ) inherited form of type 2 diabetes.

Function

At low insulin level, the GLUT -4- vesicles migrate slowly to the endosomes and are degraded there. With increasing concentration of blood sugar levels, also increases the insulin levels. Insulin mediates the fusion of the vesicles with the plasma membrane. After deflection of the vesicles to the outer membrane through insulin signaling the glucose uptake of the cell can be quickly set to the 20 - to 50 -fold increase value. After that, the transporters are resumed by endocytosis and can be used again. In fat cells can then be converted into glucose, triacylglycerols, are stored in the form of glycogen in muscle. GLUT -4 is very similar to GLUT- 1, but can not transport DHA.

Regulation

Glucose uptake by muscle cells is regulated by the number of GLUT-4 molecules in the membrane and at the same time the frequency of recycling by endocytosis. In addition, the activity of the transporter may change. The number of the GLUT -4- transporter is in this case increased primarily by the effects of insulin. The recycling rate can be slowed by muscle contraction, depolarization or lack of energy. The activity is reduced when the enzymes glyceraldehyde- 3-phosphate dehydrogenase or hexokinase II binding to GLUT-4.

GLUT-4

Function

Regulation

Further Reading