title: Mutations in AP2S1 cause familial hypocalciuric hypercalcemia type 3.
abstract: 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.
authors.affiliation: Academic Endocrine Unit, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK.
authors.forename: M Andrew
authors.initials: MA
authors.lastname: Nesbit
authors.forename: Fadil M
authors.initials: FM
authors.lastname: Hannan
authors.forename: Sarah A
authors.initials: SA
authors.lastname: Howles
authors.forename: Anita A C
authors.initials: AA
authors.lastname: Reed
authors.forename: Treena
authors.initials: T
authors.lastname: Cranston
authors.forename: Clare E
authors.initials: CE
authors.lastname: Thakker
authors.forename: Lorna
authors.initials: L
authors.lastname: Gregory
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Rimmer
authors.forename: Nigel
authors.initials: N
authors.lastname: Rust
authors.forename: Una
authors.initials: U
authors.lastname: Graham
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Morrison
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Hunter
authors.forename: Michael P
authors.initials: MP
authors.lastname: Whyte
authors.forename: Gil
authors.initials: G
authors.lastname: McVean
authors.forename: David
authors.initials: D
authors.lastname: Buck
authors.forename: Rajesh V
authors.initials: RV
authors.lastname: Thakker
mesh_terms: D033962:Adaptor Protein Complex 2 / Q000737:chemistry / Q000235:genetics*; D034002:Adaptor Protein Complex sigma Subunits / Q000737:chemistry / Q000235:genetics*; D000328:Adult; D000595:Amino Acid Sequence; D002118:Calcium / Q000378:metabolism; D017124:Conserved Sequence; D005260:Female; D006801:Humans; D006934:Hypercalcemia / Q000235:genetics* / Q000378:metabolism; D008297:Male; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D011487:Protein Conformation; D044169:Receptors, Calcium-Sensing / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment
chemical_list: C510065:AP2S1 protein, human; D033962:Adaptor Protein Complex 2; D034002:Adaptor Protein Complex sigma Subunits; D044169:Receptors, Calcium-Sensing; D002118:Calcium