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The effects of insulin vary depending on the tissue involved, e.g., insulin is most important in the uptake of glucose by muscle and adipose tissue. [2] This insulin signal transduction pathway is composed of trigger mechanisms (e.g., autophosphorylation mechanisms) that serve as signals throughout the cell. There is also a counter mechanism in ...
The extracellular type II and type I kinase receptors binding to the TGF-β ligands. Transforming growth factor-β (TGF-β) is a superfamily of cytokines that play a significant upstream role in regulating of morphogenesis, homeostasis, cell proliferation, and differentiation. [2]
Insulin is a peptide hormone containing two chains cross-linked by disulfide bridges. Insulin (/ ˈ ɪ n. sj ʊ. l ɪ n /, [5] [6] from Latin insula, 'island') is a peptide hormone produced by beta cells of the pancreatic islets encoded in humans by the insulin (INS) gene. It is the main anabolic hormone of the body. [7]
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.
Increased insulin secretion leads to hyperinsulinemia, but blood glucose levels remain within their normal range due to the decreased efficacy of insulin signaling. [4] However, the beta cells can become overworked and exhausted from being overstimulated, leading to a 50% reduction in function along with a 40% decrease in beta-cell volume. [ 9 ]
The insulin signal transduction pathway begins when insulin binds to the insulin receptor proteins. Once the transduction pathway is completed, the GLUT-4 storage vesicles becomes one with the cellular membrane. As a result, the GLUT-4 protein channels become embedded into the membrane, allowing glucose to be transported into the cell.
Two main signal transduction mechanisms have been identified, via nuclear receptors, or via transmembrane receptors. In the first one, first messenger cross through the cell membrane, binding and activating intracellular receptors localized at nucleus or cytosol , which then act as transcriptional factors regulating directly gene expression.
Through a series of kinase proteins, the proteins are constantly being phosphorylated and activated. At the end of the transduction process, the activated protein binds to the PIP 2 proteins embedded in the membrane. By doing so, the initial signal has successfully transmitted the extracellular signal.