Phosphorylation Codes in IRS-1 and IRS-2 Are Associated with the Activation/Inhibition of Insulin Canonical Signaling
Anabel Martínez Báez1, Guadalupe Ayala1, Adolfo Pedroza-Saavedra1
1Infection Disease Research Center, National Institute of Public Health, Cuernavaca 62100, Mexico.
Abstract:
Insulin receptor substrates 1 and 2 (IRS-1 and IRS-2) are signaling adaptor proteins that participate in canonical pathways, where insulin cascade activation occurs, as well as in non-canonical pathways, in which phosphorylation of substrates is carried out by a diverse array of receptors including integrins, cytokines, steroid hormones, and others. IRS proteins are subject to a spectrum of post-translational modifications essential for their activation, encompassing phosphorylation events in distinct tyrosine, serine, and threonine residues. Tyrosine residue phosphorylation is intricately linked to the activation of the insulin receptor cascade and its interaction with SH2 domains within a spectrum of proteins, including PI3K. Conversely, serine residue phosphorylation assumes a different function, serving to attenuate the effects of insulin. In this review, we have identified over 50 serine residues within IRS-1 that have been reported to undergo phosphorylation orchestrated by a spectrum of kinases, thereby engendering the activation or inhibition of different signaling pathways. Furthermore, we delineate the phosphorylation of over 10 distinct tyrosine residues at IRS-1 or IRS-2 in response to insulin, a process essential for signal transduction and the subsequent activation of PI3K.
Insights
Insulin receptor substrates (IRS-1 and IRS-2) are key signaling proteins. Their phosphorylation, particularly on serine and tyrosine residues, regulates insulin signaling pathways and cellular responses.
Area of Science:
- Cellular signaling and molecular biology
- Endocrinology and metabolic research
Background:
- Insulin receptor substrates (IRS-1 and IRS-2) are crucial adaptor proteins in insulin signaling.
- These proteins mediate both canonical insulin cascades and non-canonical pathways involving various receptors.
- Post-translational modifications, especially phosphorylation, are critical for IRS protein function.
Purpose of the Study:
- To review the diverse phosphorylation sites on IRS-1 and IRS-2.
- To elucidate the distinct roles of tyrosine and serine phosphorylation in insulin signaling.
- To highlight the regulation of signaling pathways by IRS protein modifications.
Main Methods:
- Literature review of studies on IRS-1 and IRS-2 phosphorylation.
- Analysis of reported serine and tyrosine phosphorylation sites.
- Integration of findings on kinase-mediated modifications and pathway outcomes.
Main Results:
- Over 50 serine residues on IRS-1 are phosphorylated by various kinases, modulating pathway activity.
- More than 10 distinct tyrosine residues on IRS-1/IRS-2 are phosphorylated upon insulin stimulation.
- Tyrosine phosphorylation activates the insulin receptor cascade and PI3K signaling.
Conclusions:
- IRS protein phosphorylation is a complex regulatory mechanism.
- Tyrosine phosphorylation by insulin receptor promotes signaling, while serine phosphorylation often attenuates it.
- Understanding these modifications is vital for deciphering insulin action and metabolic regulation.
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