AP2σ Mutations Impair Calcium-Sensing Receptor Trafficking and Signaling, and Show an Endosomal Pathway to Spatially Direct G-Protein Selectivity

Cell Rep. 2018 Jan 23;22(4):1054-1066. doi: 10.1016/j.celrep.2017.12.089. Epub 2018 Jan 28.

Abstract

Spatial control of G-protein-coupled receptor (GPCR) signaling, which is used by cells to translate complex information into distinct downstream responses, is achieved by using plasma membrane (PM) and endocytic-derived signaling pathways. The roles of the endomembrane in regulating such pleiotropic signaling via multiple G-protein pathways remain unknown. Here, we investigated the effects of disease-causing mutations of the adaptor protein-2σ subunit (AP2σ) on signaling by the class C GPCR calcium-sensing receptor (CaSR). These AP2σ mutations increase CaSR PM expression yet paradoxically reduce CaSR signaling. Hypercalcemia-associated AP2σ mutations reduced CaSR signaling via Gαq/11 and Gαi/o pathways. The mutations also delayed CaSR internalization due to prolonged residency time of CaSR in clathrin structures that impaired or abolished endosomal signaling, which was predominantly mediated by Gαq/11. Thus, compartmental bias for CaSR-mediated Gαq/11 endomembrane signaling provides a mechanistic basis for multidimensional GPCR signaling.

Keywords: G proteins; GPCR; adaptor protein-2; calcium signaling; clathrin-mediated endocytosis; endosomal signaling; hypercalcemia.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Protein Complex 2 / genetics*
  • Adaptor Protein Complex alpha Subunits / genetics*
  • Calcium Signaling / genetics*
  • Endosomes / metabolism*
  • GTP-Binding Proteins / metabolism*
  • Humans
  • Mutation
  • Receptors, Calcium-Sensing / genetics*

Substances

  • AP2A1 protein, human
  • Adaptor Protein Complex 2
  • Adaptor Protein Complex alpha Subunits
  • Receptors, Calcium-Sensing
  • GTP-Binding Proteins