AP2σ Mutations Impair Calcium-Sensing Receptor Trafficking and Signaling, and Show an Endosomal Pathway to Spatially...

Area of Science:

• Cellular Biology
• Molecular Signaling
• Biochemistry

Background:

• G-protein-coupled receptor (GPCR) signaling spatial control is vital for cellular responses.
• Endomembrane system's role in regulating GPCR signaling via multiple G-protein pathways is largely unknown.

Purpose of the Study:

• Investigate the impact of disease-associated adaptor protein-2σ (AP2σ) mutations on calcium-sensing receptor (CaSR) signaling.
• Elucidate the mechanisms by which AP2σ mutations affect CaSR trafficking and downstream signaling pathways.

Main Methods:

• Utilized cell-based assays to examine CaSR expression, localization, and signaling.
• Analyzed the effects of AP2σ mutations on CaSR internalization and endosomal trafficking.
• Assessed CaSR signaling through Gαq/11 and Gαi/o pathways.

Main Results:

• AP2σ mutations increased CaSR plasma membrane expression but reduced overall signaling.
• Mutations impaired CaSR internalization, leading to prolonged residency in clathrin-coated structures.
• Endosomal CaSR signaling, primarily mediated by Gαq/11, was abolished or significantly reduced.

Conclusions:

• AP2σ mutations disrupt CaSR signaling by impairing endosomal trafficking and signaling.
• Compartmental bias in CaSR-mediated Gαq/11 endomembrane signaling is a key mechanism in multidimensional GPCR regulation.
• Findings provide insights into the pathophysiology of hypercalcemia linked to AP2σ mutations.