G Protein-Coupled Receptor Kinase 6 (GRK6) Regulates Insulin Processing and Secretion via Effects on Proinsulin Conversion to Insulin

Authors

Matthew J Varney, Thomas Jefferson UniversityFollow
Wouter Steyaert, Radboud University Medical Center
Paul J Coucke, Ghent University and Ghent University Hospital
Joris R Delanghe, Ghent University
David E Uehling, Ontario Institute for Cancer Research
Babu Joseph, Ontario Institute for Cancer Research
Richard Marcellus, Ontario Institute for Cancer Research
Rima Al-Awar, University of Toronto
Jeffrey L Benovic, Thomas Jefferson UniversityFollow

Document Type

Article

Publication Date

8-25-2022

Comments

This article is the author’s final published version in Journal of Biological Chemistry, Volume 298, Issue 10, September 2022, Article number 102421.

The published version is available at https://doi.org/10.1016/j.jbc.2022.102421. Copyright © Varney et al.

Abstract

Recent studies identified a missense mutation in the gene coding for G protein-coupled receptor kinase 6 (GRK6) that segregates with type 2 diabetes (T2D). To better understand how GRK6 might be involved in T2D, we used pharmacological inhibition and genetic knockdown in the mouse β-cell line, MIN6, to determine whether GRK6 regulates insulin dynamics. We show inhibition of GRK5 and GRK6 increased insulin secretion but reduced insulin processing while GRK6 knockdown revealed these same processing defects with reduced levels of cellular insulin. GRK6 knockdown cells also had attenuated insulin secretion but enhanced proinsulin secretion consistent with decreased processing. In support of these findings, we demonstrate GRK6 rescue experiments in knockdown cells restored insulin secretion after glucose treatment. The altered insulin profile appears to be caused by changes in the proprotein convertases, the enzymes responsible for proinsulin to insulin conversion, as GRK6 knockdown resulted in significantly reduced convertase expression and activity. To identify how the GRK6-P384S mutation found in T2D patients might affect insulin processing, we performed biochemical and cell biological assays to study the properties of the mutant. We found that while GRK6-P384S was more active than WT GRK6, it displayed a cytosolic distribution in cells compared to the normal plasma membrane localization of GRK6. Additionally, GRK6 overexpression in MIN6 cells enhanced proinsulin processing, while GRK6-P384S expression had little effect. Taken together, our data show that GRK6 regulates insulin processing and secretion in a glucose-dependent manner and provide a foundation for understanding the contribution of GRK6 to T2D.

Recommended Citation

Varney, Matthew J; Steyaert, Wouter; Coucke, Paul J; Delanghe, Joris R; Uehling, David E; Joseph, Babu; Marcellus, Richard; Al-Awar, Rima; and Benovic, Jeffrey L, "G Protein-Coupled Receptor Kinase 6 (GRK6) Regulates Insulin Processing and Secretion via Effects on Proinsulin Conversion to Insulin" (2022). Department of Biochemistry and Molecular Biology Faculty Papers. Paper 222.
https://jdc.jefferson.edu/bmpfp/222

Creative Commons License

This work is licensed under a Creative Commons Attribution 4.0 License.

PubMed ID

36030052

Language

English