Gα11 mutation in mice causes hypocalcemia rectifiable by calcilytic therapy
Caroline M. Gorvin, Fadil M. Hannan, Sarah A. Howles, Valerie N. Babinsky, Sian E. Piret, Angela Rogers, Andrew J. Freidin, Michelle Stewart, Anju Paudyal, Tertius A. Hough, M. Andrew Nesbit, Sara Wells, Tonia L. Vincent, Stephen D.M. Brown, Roger D. Cox, Rajesh V. Thakker
Caroline M. Gorvin, Fadil M. Hannan, Sarah A. Howles, Valerie N. Babinsky, Sian E. Piret, Angela Rogers, Andrew J. Freidin, Michelle Stewart, Anju Paudyal, Tertius A. Hough, M. Andrew Nesbit, Sara Wells, Tonia L. Vincent, Stephen D.M. Brown, Roger D. Cox, Rajesh V. Thakker
View: Text | PDF
Research Article Endocrinology Metabolism

Gα11 mutation in mice causes hypocalcemia rectifiable by calcilytic therapy

Abstract

Heterozygous germline gain-of-function mutations of G-protein subunit α11 (Gα11), a signaling partner for the calcium-sensing receptor (CaSR), result in autosomal dominant hypocalcemia type 2 (ADH2). ADH2 may cause symptomatic hypocalcemia with low circulating parathyroid hormone (PTH) concentrations. Effective therapies for ADH2 are currently not available, and a mouse model for ADH2 would help in assessment of potential therapies. We hypothesized that a previously reported dark skin mouse mutant (Dsk7) — which has a germline hypermorphic Gα11 mutation, Ile62Val — may be a model for ADH2 and allow evaluation of calcilytics, which are CaSR negative allosteric modulators, as a targeted therapy for this disorder. Mutant Dsk7/+ and Dsk7/Dsk7 mice were shown to have hypocalcemia and reduced plasma PTH concentrations, similar to ADH2 patients. In vitro studies showed the mutant Val62 Gα11 to upregulate CaSR-mediated intracellular calcium and MAPK signaling, consistent with a gain of function. Treatment with NPS-2143, a calcilytic compound, normalized these signaling responses. In vivo, NPS-2143 induced a rapid and marked rise in plasma PTH and calcium concentrations in Dsk7/Dsk7 and Dsk7/+ mice, which became normocalcemic. Thus, these studies have established Dsk7 mice, which harbor a germline gain-of-function Gα11 mutation, as a model for ADH2 and have demonstrated calcilytics as a potential targeted therapy.

Authors

Caroline M. Gorvin, Fadil M. Hannan, Sarah A. Howles, Valerie N. Babinsky, Sian E. Piret, Angela Rogers, Andrew J. Freidin, Michelle Stewart, Anju Paudyal, Tertius A. Hough, M. Andrew Nesbit, Sara Wells, Tonia L. Vincent, Stephen D.M. Brown, Roger D. Cox, Rajesh V. Thakker

×

Figure 2

Structural characterization of the Ile62Val Gα11 mutation.

Options: View larger image (or click on image) Download as PowerPoint
Structural characterization of the Ile62Val Gα11 mutation. (A) Genomic o...
(A) Genomic organization of Gna11 showing location of the Ile62Val mutation. The Gα11 GTPase domain (encoded by exon 1, 5′portion of exon 2, 3′ portion of exon 4 and exons 5–7) is connected to the helical domain (encoded by the 3′ portion of exon 2, exon 3, and 5′ portion of exon 4) by the linker 1 (L1) and 2 (L2) peptides. The Ile62Val mutation (red) lies within the α1 helix (green). The location of reported ADH2 mutations are indicated (black). (B) Multiple protein sequence alignment of residues comprising the α1 helix and L1 peptide of Gα11-subunit orthologs (top) and Gα-subunit paralogs (bottom). Conserved residues are shown in gray. The WT (Ile) and Dsk7 mutant (m) (Val) residues are shown in red. (C) Homology model of the Gα11 protein. The Gα helical (blue) and GTPase (green) domains are connected by the L1 and L2 peptides (gray). GDP (black) is bound at the interdomain interface. Previously reported residues mutated in ADH2 are shown in yellow. The mutated Ile62 residue is shown in red. (D) Close-up view of the Ile62 residue, which lies within a hydrophobic cluster of residues (blue spheres) on α1, α5, and β1 of the GTPase domain and near to the interdomain interface (dotted line) and GDP binding site.