The P300 acetyltransferase inhibitor C646 promotes membrane translocation of insulin receptor protein substrate and interaction with the insulin receptor

Jinghua Peng,Balamurugan Ramatchandirin,Yu Wang,Alexia Pearah,Kopperuncholan Namachivayam,Risa M Wolf,Kimberley Steele,Krishnan Mohankumar,Liqing Yu,Shaodong Guo,Morris F White,Akhil Maheshwari,Ling He

doi:10.1016/j.jbc.2022.101621

Abstract

Inhibition of P300 acetyltransferase activity by specific inhibitor C646 has been shown to improve insulin signaling. However, the underlying molecular mechanism of this improvement remains unclear. In this study, we analyzed P300 levels of obese patients and found that they were significantly increased in liver hepatocytes. In addition, large amounts of P300 appeared in the cytoplasm. Inhibition of P300 acetyltransferase activity by C646 drastically increased tyrosine phosphorylation of the insulin receptor protein substrates (IRS1/2) without affecting the tyrosine phosphorylation of the beta subunit of the insulin receptor (IRβ) in hepatocytes in the absence of insulin. Since IRS1/2 requires membrane translocation and binding to inositol compounds for normal functions, we also examined the role of acetylation on binding to phosphatidylinositol(4,5)P2 and found that IRS1/2 acetylation by P300 reduced this binding. In contrast, we show that inhibition of IRS1/2 acetylation by C646 facilitates IRS1/2 membrane translocation. Intriguingly, we demonstrate that C646 activates IRβ′s tyrosine kinase activity and directly promotes IRβ interaction with IRS1/2, leading to the tyrosine phosphorylation of IRS1/2 and subsequent activation of insulin signaling even in the absence of insulin. In conclusion, these data reveal the unique effects of C646 in activating insulin signaling in patients with obesity and diabetes.

Highlights

Obesity, which has reached alarming levels (IRS1/2) without affecting the tyrosine phosphorylation of the beta subunit of the worldwide, is associated with an increased risk of metabolic abnormalities including type 2 diabetes insulin receptor (IR in hepatocytes in the (T2D)
Insulin inositol compounds for normal functions, we deficiency in T1D as well as insulin resistance examined the role of acetylation on and insufficient insulin secretion from impaired binding to phosphatidylinositol[4,5]P2, and found that IRS1/2 acetylation by P300 reduced this binding
We found that LPS can induce P300 in hepatocytes via reduction of the ubiquitination and degradation of P300, and elevated P300 impairs insulin signaling by acetylating IRS1 and 2 [27,35]

Summary

Introduction

Obesity, which has reached alarming levels (IRS1/2) without affecting the tyrosine phosphorylation of the beta subunit of the worldwide, is associated with an increased risk of metabolic abnormalities including type 2 diabetes insulin receptor (IR in hepatocytes in the (T2D). To test the effects of P300 acetyltransferase activity on insulin signaling, we treated Hepa1-6 cells with P300 acetyltransferase-specific inhibitor C646 and control inactive compound C37 [28,29] in the absence of both insulin and FBS, and found that C646 treatment led to over 10-fold increase in the tyrosine phosphorylation of IRS1 and 2 (Fig. 2A, B), along with their mobility shift that may be caused by their tyrosine phosphorylation (Supplementary Fig. 2C, D).

Results

Conclusion