Sandbox Reserved 427: Difference between revisions

The insulin receptor is a tyrosine kinase, that is a type of ligand-activated receptor kinase. Insulin receptors are expressed at the cell surface as disulfide-linked homodimers composed of alpha/beta <scene name='Sandbox_Reserved_427/Rcb_monomer_fabsfaded/1'>monomers</scene>. The folded over conformation of the ectodomain places ligands in the correct relative positions for activity. ('''green scene''') The receptor mediates activity by the addition of phosphate to tyrosines on specific proteins in cell

Insulin receptors are found in many diverse organisms organisms, from cnidarians and insects to humans. In humans, correctly functioning insulin receptors are essential for maintaining glucose levels in the blood. The insulin receptor also has role in growth and development (through insulin growth factor II); studies have shown that signalling through IGF2 plays a role in the mediation embryonic growth (Kitamura et al).

In everyday function, insulin receptor substrate 1 (IRS-1) binding leads to increase in the high-affinity glucose transporter (Glut4) molecules on the outer membrane of the cell in muscle and adipose tissue. Glut4 mediates the transport of glucose into the cell, so an increase in Glut4 leads to increased glucose uptake.

Maintaining appropriate blood glucose levels is essential for appropriate life-sustaining metabolic function, and insulin receptor malfunction is associated with several severe diseases. Insulin insensitivity, or decreased insulin receptor signalling, leads to diabetes mellitus type 2. Type 2 diabetes is also known as non-insulin-dependent or adult onset diabetes, and is believed to be caused by a combination of obesity and genetic predisposition. In type 2 diabetes, cells are unable to uptake glucose due to decreased insulin receptor signaling, which leads to hyperglycemia (increased circulating glucose). Type 2 diabetes can be managed with dietary and lifestyle modifications to aid in proper metabolism.

 

Mutations in both copies of the insulin receptor gene causes Donohue syndrome, which is also known as leprechaunism. Donohue syndrome is an autosomal recessive disorder that results in a totally non-functional insulin receptor. The disorder results in distorted facial features, severe growth retardation, and often death within a year.