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Dual mode of glucagon receptor internalization: role of PKCα, GRKs and β-arrestins

Lada Krilov1, Amy Nguyen, Teruo Miyazaki

  • 1Gastroenterology Research Laboratory, Digestive Diseases Center, Department of Biochemistry and Molecular Biology, The George Washington University, Washington, DC, USA.

Experimental Cell Research
|October 18, 2011
PubMed

Insights

Glucagon receptor (GR) internalization is enhanced by protein kinase C alpha (PKCα) and G protein-coupled receptor kinases (GRKs). This process involves both clathrin- and caveolin-mediated endocytosis, crucial for understanding diabetes treatments.

Area of Science:

  • Endocrinology
  • Cell Biology
  • Pharmacology

Background:

  • Elevated glucagon levels are linked to diabetes and liver diseases, driving hyperglycemia via increased hepatic glucose production.
  • Blocking glucagon receptor (GR) signaling is a therapeutic strategy for hyperglycemia.
  • Understanding GR desensitization and downregulation mechanisms can reveal novel drug targets.

Purpose of the Study:

  • To investigate the mechanisms of glucagon receptor (GR) internalization.
  • To elucidate the roles of protein kinase C alpha (PKCα), G protein-coupled receptor kinases (GRKs), and β-arrestins in GR internalization.

Main Methods:

  • Utilized HEK-293 cells expressing GR (HEK-GR cells) and primary hepatocytes.
  • Assessed GR internalization, phosphorylation, and colocalization with signaling proteins (PKCα, GRKs, β-arrestins, Cav-1) using glucagon stimulation and overexpression techniques.
  • Investigated the involvement of clathrin- and caveolin-mediated endocytosis pathways.

Main Results:

  • Glucagon stimulation increased GR internalization by 25-40% in HEK-GR cells, an effect potentiated by PKCα.
  • PKCα, GRKs (GRK2, GRK3, GRK5), β-arrestin1, and β-arrestin2 were recruited to the plasma membrane and colocalized with GR upon glucagon treatment.
  • GR internalization was found to utilize both clathrin- and caveolin-mediated endocytosis pathways.

Conclusions:

  • PKCα plays a significant role in enhancing glucagon-mediated GR internalization.
  • GRKs and β-arrestins are key mediators of GR internalization, suggesting their involvement in GR signaling regulation.
  • The dual utilization of clathrin- and caveolin-mediated endocytosis highlights the complex trafficking mechanisms of the GR.

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