DOC2b Enhances β-Cell Function via a Novel Tyrosine Phosphorylation-Dependent Mechanism

Area of Science:

• Cell Biology
• Endocrinology
• Molecular Biology

Background:

• The Double C2 domain Β (DOC2b) protein is essential for glucose-stimulated insulin secretion (GSIS) in pancreatic beta cells.
• The precise molecular mechanisms underlying DOC2b's role in GSIS are not fully understood.

Purpose of the Study:

• To elucidate the mechanism of DOC2b's involvement in GSIS.
• To identify the kinase responsible for DOC2b modification and its downstream signaling pathways.

Main Methods:

• Biochemical analysis of primary human islets and beta-cell lines.
• Site-directed mutagenesis of DOC2b (Y301 mutants).
• Coimmunoprecipitation assays and Western blotting.
• Analysis of VAMP2 protein localization and ERM protein activation.

Main Results:

• DOC2b undergoes rapid tyrosine phosphorylation upon glucose stimulation, mediated by YES kinase.
• Phosphorylation at Y301 is critical for DOC2b interaction with YES kinase and enhances VAMP2 presence at the plasma membrane.
• Tyrosine-phosphorylated DOC2b activates ERM proteins, promoting insulin granule localization to the plasma membrane and boosting GSIS.
• ERM protein knockdown impairs DOC2b-mediated enhancement of GSIS.

Conclusions:

• Glucose induces posttranslational modification of DOC2b in beta cells, involving YES kinase and Y301 phosphorylation.
• Phosphorylated DOC2b regulates GSIS through ERM-mediated insulin granule exocytosis.
• This study reveals a novel regulatory pathway for GSIS, offering potential therapeutic targets for diabetes.