Phase separation of insulin receptor substrate 1 drives the formation of insulin/IGF-1 signalosomes

Abstract

As a critical node for insulin/IGF signaling, insulin receptor substrate 1 (IRS-1) is essential for metabolic regulation. A long and unstructured C-terminal region of IRS-1 recruits downstream effectors for promoting insulin/IGF signals. However, the underlying molecular basis for this remains elusive. Here, we found that the C-terminus of IRS-1 undergoes liquid-liquid phase separation (LLPS). Both electrostatic and hydrophobic interactions were seen to drive IRS-1 LLPS. Self-association of IRS-1, which was mainly mediated by the 301–600 region, drives IRS-1 LLPS to form insulin/IGF-1 signalosomes. Moreover, tyrosine residues of YXXM motifs, which recruit downstream effectors, also contributed to IRS-1 self-association and LLPS. Impairment of IRS-1 LLPS attenuated its positive effects on insulin/IGF-1 signaling. The metabolic disease-associated G972R mutation impaired the self-association and LLPS of IRS-1. Our findings delineate a mechanism in which LLPS of IRS-1-mediated signalosomes serves as an organizing center for insulin/IGF-1 signaling and implicate the role of aberrant IRS-1 LLPS in metabolic diseases.

The dynamic clustering of insulin receptor underlies its signaling and is disrupted in insulin resistance

“…Recent studies have shown that the components of diverse signaling pathways, including those involving receptor tyrosine kinases, T-cell receptor, WNT, TGF-β, and JAK/STAT, involve the assembly of protein molecules into condensates at the plasma membrane, in the cytoplasm and nucleus [24][25][26][27][28][29][30][31][32][33] . Our evidence indicates that this is also the case for the insulin receptor, as the IR clusters observed here have characteristics expected of condensates.…”

“…Recent reports indicate that signaling factors can form dynamic clusters with properties and characteristics expected of biomolecular condensates [24][25][26][27][28][29][30][31][32][33] . Biomolecular condensates are cellular compartments wherein proteins and nucleic acids concentrate without being physically delimitated by a membrane 34 .…”

“…Biomolecular condensates are cellular compartments wherein proteins and nucleic acids concentrate without being physically delimitated by a membrane 34 . Condensate formation and condensate properties have been shown to contribute to diverse types of cellular signaling [24][25][26][27][28][29][30][31][32][33] . For example, evidence suggests that T-cell receptor activation causes the formation of condensate compartments at the plasma membrane that incorporate signaling components and promote signaling 24,25 , and similar observations were recently reported for various RTKs 30 .…”

Fluorogenic methodology for visualization of phase separation in chemical biology

“…61 Chandra 62 et al also indicated that phase separation is involved in NUP98 fusion oncoprotein leukaemia transformation. In addition, with more recent studies hinting at the role of abnormal IRS-1 LLPS in metabolic diseases 63 and growing evidence that LLPS is involved in immune responses to viral diseases and antiviral infections, it could provide a new framework to interpret and understand the mechanisms of infectious diseases and create potential new therapeutic pathways. Many viruses can also form viral replication condensates through LLPS.…”

A novel view of the insulin signaling pathway based on prediction of protein structure by the AI platform AlphaFold

“…A recent study showed that the self‐aggregation of IRS via its COOH‐terminal IDR triggers LLPS and the formation of signalosomes containing PI3K and Grb2 8 . Furthermore, a mutation of IRS (G972R in IRS1) that is located in this IDR and is associated with the risk of type 2 diabetes impairs the self‐aggregation of IRS and signalosome formation.…”