Adaptor protein-2 (AP2), a central component of clathrin-coated vesicles (CCVs), is pivotal in clathrin-mediated endocytosis, which internalizes plasma membrane constituents such as G protein-coupled receptors (GPCRs). AP2, a heterotetramer of α, β, μ and σ subunits, links clathrin to vesicle membranes and binds to tyrosine- and dileucine-based motifs of membrane-associated cargo proteins. Here we show that missense mutations of AP2 σ subunit (AP2S1) affecting Arg15, which forms key contacts with dileucine-based motifs of CCV cargo proteins, result in familial hypocalciuric hypercalcemia type 3 (FHH3), an extracellular calcium homeostasis disorder affecting the parathyroids, kidneys and bone. We found AP2S1 mutations in >20% of cases of FHH without mutations in calcium-sensing GPCR (CASR), which cause FHH1. AP2S1 mutations decreased the sensitivity of CaSR-expressing cells to extracellular calcium and reduced CaSR endocytosis, probably through loss of interaction with a C-terminal CaSR dileucine-based motif, whose disruption also decreased intracellular signaling. Thus, our results identify a new role for AP2 in extracellular calcium homeostasis.

Original publication

DOI

10.1038/ng.2492

Type

Journal article

Journal

Nature genetics

Publication Date

01/2013

Volume

45

Pages

93 - 97

Addresses

Academic Endocrine Unit, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK.

Keywords

Humans, Hypercalcemia, Calcium, Receptors, Calcium-Sensing, Adaptor Protein Complex 2, Adaptor Protein Complex sigma Subunits, Sequence Alignment, Amino Acid Sequence, Conserved Sequence, Protein Conformation, Mutation, Models, Molecular, Molecular Sequence Data, Adult, Female, Male