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The insulin receptor (IR) is a transmembrane receptor that is activated by insulin, IGF-I, IGF-II and belongs to the large class of receptor tyrosine kinase. [5] Metabolically, the insulin receptor plays a key role in the regulation of glucose homeostasis; a functional process that under degenerate conditions may result in a range of clinical manifestations including diabetes and cancer.
Insulin receptor substrate 1 (IRS-1) is a signaling adapter protein that in humans is encoded by the IRS1 gene. [5] It is a 180 kDa protein with amino acid sequence of 1242 residues. [ 6 ] It contains a single pleckstrin homology (PH) domain at the N-terminus and a PTB domain ca. 40 residues downstream of this, followed by a poorly conserved C ...
The effects of insulin are initiated by its binding to a receptor, the insulin receptor (IR), present in the cell membrane. The receptor molecule contains an α- and β subunits. Two molecules are joined to form what is known as a homodimer.
Insulin receptor substrate (IRS) is an important ligand in the insulin response of human cells. IRS-1, for example, is an IRS protein that contains a phosphotyrosine binding-domain . In addition, the insulin receptor contains a NPXY motif. The PTB-domain binds the NPXY sequence. Thus, the insulin receptor binds IRS.
Conversely, when the blood glucose levels are too high, the pancreas is signaled to release insulin. Insulin is delivered to the liver and other tissues throughout the body (e.g., muscle, adipose). When the insulin is introduced to the liver, it connects to the insulin receptors already present, that is tyrosine kinase receptor. [15]
Additionally, while proinsulin and insulin have structural differences, proinsulin does demonstrate some affinity for the insulin receptor. Due to the relative similarities in structure, proinsulin can produce between 5% and 10% of the metabolic activity similarly induced by insulin. [3]
This receptor mediates the effects of IGF-1, which is a polypeptide protein hormone similar in molecular structure to insulin. IGF-1 plays an important role in growth and continues to have anabolic effects in adults – meaning that it can induce hypertrophy of skeletal muscle and other target tissues.
The glucagon-like peptide-1 receptor (GLP1R) is a G protein-coupled receptor (GPCR) found on beta cells of the pancreas and on neurons of the brain. It is involved in the control of blood sugar level by enhancing insulin secretion. In humans it is synthesised by the gene GLP1R, which is present on chromosome 6.