GLUT4glukosetransportører

GLUT4, or glucose transporter type 4, is a facilitative glucose transporter encoded by the SLC2A4 gene. It is primarily expressed in insulin-sensitive tissues, notably adipose tissue and skeletal muscle, with a contribution in cardiac muscle. GLUT4 plays a central role in insulin-regulated glucose uptake, supporting postprandial glucose disposal and energy storage.

Under basal conditions, GLUT4 resides in intracellular storage vesicles rather than on the cell surface. In response to insulin, signaling pathways trigger translocation of these vesicles to the plasma membrane, increasing glucose uptake into cells. The insulin signaling cascade involves the insulin receptor, IRS proteins, phosphoinositide 3-kinase (PI3K), and AKT, particularly AKT2. Proteins such as AS160 (TBC1D4) and TBC1D1 regulate vesicle trafficking by modulating Rab GTPases that control GLUT4 movement and docking at the membrane. Exercise can also promote GLUT4 translocation via AMP-activated protein kinase (AMPK), providing an insulin-independent mechanism for increasing glucose uptake.

Physiologically, GLUT4 is essential for efficient postprandial glucose clearance and energy storage in muscle and fat tissue. Alterations in GLUT4 expression or trafficking are associated with insulin resistance and metabolic diseases, including type 2 diabetes and obesity. Genetic variations in SLC2A4 have been investigated for potential links to insulin sensitivity, though findings vary across populations.

Structurally, GLUT4 belongs to the major facilitator superfamily with 12 transmembrane helices that form the glucose transport pathway. Regulation occurs both at the transcriptional level and through rapid, signal-dependent trafficking to and from intracellular compartments.