Phosphoproteomics reveals rewiring of the insulin signaling network and multi-nodal defects in insulin resistance

The failure of metabolic tissues to respond to insulin is an early marker of type 2 diabetes. Here, the authors show, using global phosphoproteomics, that insulin resistance is caused by a marked rewiring of both canonical and non-canonical insulin signalling, and includes dysregulated GSK3 activity. The failure of metabolic tissues to appropriately respond to insulin (insulin resistance) is an early marker in the pathogenesis of type 2 diabetes. Protein phosphorylation is central to the adipocyte insulin response, but how adipocyte signaling networks are dysregulated upon insulin resistance is unknown. Here we employ phosphoproteomics to delineate insulin signal transduction in adipocyte cells and adipose tissue. Across a range of insults causing insulin resistance, we observe a marked rewiring of the insulin signaling network. This includes both attenuated insulin-responsive phosphorylation, and the emergence of phosphorylation uniquely insulin-regulated in insulin resistance. Identifying dysregulated phosphosites common to multiple insults reveals subnetworks containing non-canonical regulators of insulin action, such as MARK2/3, and causal drivers of insulin resistance. The presence of several bona fide GSK3 substrates among these phosphosites led us to establish a pipeline for identifying context-specific kinase substrates, revealing widespread dysregulation of GSK3 signaling. Pharmacological inhibition of GSK3 partially reverses insulin resistance in cells and tissue explants. These data highlight that insulin resistance is a multi-nodal signaling defect that includes dysregulated MARK2/3 and GSK3 activity.

Automated summary

The failure of metabolic tissues to respond to insulin is an early marker of type 2 diabetes. Using global phosphoproteomics, the authors demonstrate that insulin resistance is caused by a significant rewiring of insulin signaling pathways, leading to dysregulated GSK3 activity. Dysregulation of protein phosphorylation plays a crucial role in adipocyte insulin response and insulin resistance. Through phosphoproteomics, the researchers reveal a marked rewiring of the insulin signaling network and identify common dysregulated phosphosites and subnetworks that contribute to insulin resistance, including non-canonical regulators MARK2/3 and GSK3. Inhibition of GSK3 partially reverses insulin resistance in cells and tissue explants.