The key difference between GLUT2 and GLUT4 is that GLUT2 does not rely on insulin to carry out protein-facilitated glucose movement across cell membranes. In contrast, GLUT4 relies on insulin to carry out protein-facilitated glucose movement across cell membranes.
Glucose is a vital source of energy for all life forms. Glucose transporters are a group of membrane proteins that facilitate glucose transportation across cell membranes. This process takes place through a facilitated diffusion mechanism. These glucose transporters can be found in all phyla. GULT or SLC2A is a protein family found in most mammalian cells. There are 14 GLUTS encoded by the human genome. GLUT2 and GLUT4 are two types of glucose transporters.
CONTENTS
1. Overview and Key Difference
2. What is GLUT2
3. What is GLUT4
4. Similarities – GLUT2 and GLUT4
5. GLUT2 vs GLUT4 in Tabular Form
6. Summary – GLUT2 vs GLUT4
What is GLUT2 (Glucose Transporter 2)?
Glucose transporter 2 (GLUT2) is a transmembrane carrier protein that allows protein-facilitated glucose transportation across plasma membranes. It is also known as solute carrier family 2 member 2. GLUT2 is the principal transporter for transferring glucose between the liver and blood. This transporter protein is found in cell membranes of the liver, pancreatic β cells, hypothalamus, the basolateral membrane of the small intestine, and the basolateral membrane of renal tubular cells. Moreover, GLUT2 does not rely on insulin for facilitated diffusion. In humans, this protein is encoded by the gene SLC2A2.
Figure 01: GLUT2
GLUT2 is a very efficient carrier protein for glucose. GLUT2 also can carry glucosamine. When the glucose concentration in the lumen of the small intestine is above 30 mM, GLUT2 is up-regulated at the brush border membrane. This enhances the glucose transportation capacity. Furthermore, basolateral GLUT2 in enterocytes also aids the transportation of fructose into the bloodstream through glucose-dependent cotransport. Defects in the gene of SLC2A2 cause a particular type of glycogen storage disease known as Fanconi-Bickel syndrome.
What is GLUT4?
GLUT4 is an insulin-dependent transmembrane carrier protein that allows protein-facilitated glucose movement across cell membranes. It is also known as solute carrier family 2 member 4 protein. GLUT4 is encoded by the human gene SLC2A4. GLUT4 is an insulin-regulated protein that is primarily found in adipose tissues and striated muscles (skeletal and cardiac muscles). This protein was first identified by David James in 1988. The gene that encodes for this protein was cloned and mapped in 1989. The main function of GLUT4 is the insulin-regulated glucose uptake into fat and muscle cells.
Figure 02: GLUT4
Under low insulin conditions, most GLUT4 proteins are sequestered in the intracellular vesicles in muscle and fat cells, which are GLUT4 storage vesicles. When the insulin level is increased, the GLUT4 in transport vesicles are quickly incorporated into the plasma membrane of the cell. This causes the uptake of glucose into the cells. According to a different analysis, it is suggested that there is a relationship between GLUT4 polymorphism and human diseases, including insulin resistance, type 2 diabetes, and obstructive sleep apnea.
What are the Similarities Between GLUT2 and GLUT4?
- GLUT2 and GLUT4 are two different types of glucose transporters.
- They belong to the GULT or SLC2A protein family.
- They are in the GULT proteins class I.
- Both proteins are found in most mammalian cells.
- They use a facilitated diffusion mechanism to transport glucose into the cell.
- The defects in genes producing these proteins cause human diseases.
What is the Difference Between GLUT2 and GLUT4?
GLUT2 is an insulin-independent transmembrane carrier protein that carries out facilitated glucose movement across the cell membranes, while GLUT4 is an insulin-dependent transmembrane carrier protein that employs facilitated glucose movement across the cell membranes. Thus, this is the key difference between GLUT2 and GLUT4. Furthermore, GLUT2 is found in cell membranes of the liver, pancreatic β cells, hypothalamus, the basolateral membrane of the small intestine, and basolateral membrane of renal tubular cells. On the other hand, GLUT4 is found in adipose tissue, skeletal muscle, and cardiac muscle.
The below infographic presents the differences between GLUT2 and GLUT4 in tabular form for side by side comparison.
Summary – GLUT2 vs GLUT4
GLUT2 and GLUT4 are two types of glucose transporters in the GULT or SLC2A carrier protein family. They transport glucose into the cell through a facilitated diffusion mechanism. GLUT2 does not depend on insulin to carry out protein-facilitated glucose movement across the cell membranes. In contrast, GLUT4 relies on insulin to carry out protein-facilitated glucose movement across the cell membranes. So, this is the key difference between GLUT2 and GLUT4.
Reference:
1. “Glucose Transporter 2.” An Overview | ScienceDirect Topics.
2. Bryant, Nia J., et al. “Regulated Transport of the Glucose Transporter GLUT4.” Nature News, Nature Publishing Group.
Image Courtesy:
1. “Glut2basal” By QuodScripsiScripsi – Own work (CC0) via Commons Wikimedia
2. “Insulin glucose metabolism” By User Meiquer – English Wikipedia (CC BY-SA 3.0) via Commons Wikimedia
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