Abstract
Insulin receptor substrate 2 (IRS2) is an essential adaptor that mediates signaling downstream of the insulin receptor and other receptor tyrosine kinases. Transduction through IRS2-dependent pathways is important for coordinating metabolic homeostasis, and dysregulation of IRS2 causes systemic insulin signaling defects. Despite the importance of maintaining proper IRS2 abundance, little is known about what factors mediate its protein stability. We conducted an unbiased proteomic screen to uncover novel substrates of the Anaphase Promoting Complex/Cyclosome (APC/C), a ubiquitin ligase that controls the abundance of key cell cycle regulators. We found that IRS2 levels are regulated by APC/C activity and that IRS2 is a direct APC/C target in G1 Consistent with the APC/C's role in degrading cell cycle regulators, quantitative proteomic analysis of IRS2-null cells revealed a deficiency in proteins involved in cell cycle progression. We further show that cells lacking IRS2 display a weakened spindle assembly checkpoint in cells treated with microtubule inhibitors. Together, these findings reveal a new pathway for IRS2 turnover and indicate that IRS2 is a component of the cell cycle control system in addition to acting as an essential metabolic regulator.
Highlights
The insulin and insulin-like growth factor 1 receptors (IR/IGF1R) are receptor tyrosine kinases that control metabolism, differentiation, and growth
We demonstrate that Insulin receptor substrate 2 (IRS2), but not IRS1, is a direct target of APC/CCdh1, thereby establishing a novel mode by which
We demonstrate that IRS2 is stabilized by Anaphase Promoting Complex/Cyclosome (APC/C) inhibition and Cdh1 knockdown in multiple cell types and that this depends on IRS2’s C-terminal D-box motif
Summary
The insulin and insulin-like growth factor 1 receptors (IR/IGF1R) are receptor tyrosine kinases that control metabolism, differentiation, and growth. Upon ligand binding at the cell surface, the activated IR/IGF1R undergoes a conformational change that allows it to auto-phosphorylate tyrosine residues on its cytoplasmic subunits [1] This facilitates the recruitment and phosphorylation of insulin receptor substrate (IRS) proteins, which serve as scaffolds to initiate downstream signaling [2]. The ubiquitin-mediated proteolysis of IRS proteins is important for restraining signaling through the IR/IGF1R Both IRS proteins are targeted for proteasomal destruction following persistent insulin or IGF1 stimulation in a negative feedback loop that attenuates PI3K-AKT signaling [2, 7]. We further show that genetic deletion of IRS2 perturbs spindle assembly checkpoint function Taken together, these data establish a role for IRS2 in normal cell cycle progression, revealing new connections between an essential component of the growth factor signaling network and cell cycle regulation
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
