Spatiotemporal regulation of insulin signaling by liquid-liquid phase separation

Insulin signals through its receptor to recruit insulin receptor substrates (IRS) and phosphatidylinositol 3-kinase (PI3K) to the plasma membrane for production of phosphatidylinositol-3,4,5-trisphosphate (PIP3) from phosphatidylinositol-4,5-bisphosphate [PI(4,5)P2], which consequently activates protein kinase B (PKB). How insulin signals transduce from the plasma membrane into the cytoplasm is not clearly understood. Here we show that liquid-liquid phase separation (LLPS) plays a critical role in spatiotemporal control of insulin signaling through regulating multiple components including IRS1. Both protein concentration and insulin stimulation can drive the formation of intracellular IRS1 condensates through LLPS. Components including PI(4,5)P2, p85-PI3K and PDK1 are constitutively present in IRS1 condensates whereas production of PIP3 and recruitment of PKB in them are induced by insulin. Thus, IRS1 condensates function as intracellular signal hubs to mediate insulin signaling, whose formation is impaired in insulin resistant cells. Collectively, these data reveal an important function of LLPS in spatiotemporal control of insulin signaling.

Automated summary

This study reveals the critical role of liquid-liquid phase separation (LLPS) in the spatiotemporal control of insulin signaling. LLPS regulates multiple components, including IRS1, and is involved in the formation of intracellular IRS1 condensates. Insulin stimulation and protein concentration drive the formation of IRS1 condensates, which function as intracellular signal hubs for insulin signaling. Impairment of IRS1 condensate formation is observed in insulin resistant cells. Overall, LLPS plays an important role in the regulation of insulin signaling.