scholarly journals Identification of a G‐Protein Subunit‐α11 Gain‐of‐Function Mutation, Val340Met, in a Family With Autosomal Dominant Hypocalcemia Type 2 (ADH2)

2016 ◽  
Vol 31 (6) ◽  
pp. 1207-1214 ◽  
Author(s):  
Sian E Piret ◽  
Caroline M Gorvin ◽  
Alistair T Pagnamenta ◽  
Sarah A Howles ◽  
Treena Cranston ◽  
...  
Keyword(s):  
G Protein ◽  
Autosomal Dominant ◽  
Protein Subunit ◽  
Gain Of Function ◽  
Autosomal Dominant Hypocalcemia

scholarly journals Autosomal Dominant Hypocalcemia Due to a GNA11 Variant: The First Case in Japan

2021 ◽  
Vol 5 (Supplement_1) ◽  
pp. A183-A183
Author(s):  
Ichiro Yamauchi ◽  
Yohei Ueda ◽  
Taku Sugawa ◽  
Takuro Hakata ◽  
Haruka Fujita ◽  
...  
Keyword(s):  
G Protein ◽  
Serum Calcium Level ◽  
Autosomal Dominant ◽  
Serum Phosphate ◽  
Serum Phosphate Level ◽  
Protein Subunit ◽  
Gain Of Function ◽  
Gene Coding ◽  
Autosomal Dominant Hypocalcemia

Abstract Background: Autosomal dominant hypocalcemia (ADH) is characterized by hypocalcemia and hyperphosphatemia due to hypoparathyroidism. ADH type 1 is caused by gain-of-function variants in CASR gene coding the calcium-sensing receptor. Recently, ADH type 2 caused by gain-of-function variants in GNA11 gene coding G-protein subunit α11 has been recognized. Case: A 32-year-old female patient visited our hospital because she suffered from hyperhidrosis, exertional dyspnea, and palpitations. She had a past medical history of paroxysmal kinesigenic dyskinesia confirmed by genetic analysis of PRRT2. Although her sister has unspecified epilepsy, no members of her kindred have episodes of tetany. Her height was 155.7 cm and weight was 64.1 kg. She had goiter with tremor and tachycardia and was diagnosed as Graves’ disease (fT3 >32.55 pg/mL, fT4 >7.77 ng/dL, TSH <0.005 µIU/mL, and TRAb 36.9 IU/L). Thiamazole therapy ameliorated her hyperthyroidism, while serum calcium level was low (7.5 mg/dL) and serum phosphate level was slight high (5.1 mg/dL). Hypoparathyroidism was confirmed because intact-PTH was relatively low (20 pg/mL) under the hypocalcemia. Her episode of tetany that she could not sit on her heels from childhood and her basal ganglia calcification in head CT scan suggest the long disease duration. Germline whole exome sequence detected a rare variant in GNA11 gene; c.1023C>A resulted in p.Phe341Leu. There were no relevant pathogenic variants in other candidate genes such as CASR, PTH, and GCM2. Treatment with 2 µg/day of alfacalcidol and 1200 mg/day of calcium aspartate could not normalize serum calcium level (7.0 mg/dL) and serum phosphate level (5.3 mg/dL) even after 1 year. Conclusions: The pathogenicity of the variant, p.Phe341Leu, in GNA11 gene was previously confirmed [1]. ADH type 2 is extremely rare as our literature review found only four previous reports; 17 patients in 5 families [1–4]. Phenotypes of the present case are mild and skeletal growth is normal. Meanwhile, we are having difficulty in management of her hypocalcemia, even though Graves’ disease might affect her bone metabolism. Optimal therapy for ADH type 2 needs further investigation. References: [1] Nesbit et al. Mutations Affecting G-protein Subunit α11 in Hypercalcemia and Hypocalcemia. N Engl J Med. 2013; 368: 2476–2486. [2] Li et al. Autosomal Dominant Hypoparathyroidism Caused by Germline Mutation in GNA11: Phenotypic and Molecular Characterization. J Clin Endocrinol Metab. 2014; 99: 1774–83. [3] Piret et al. Identification of a G-Protein Subunit-α11 Gain-of-Function Mutation, Val340Met, in a Family With Autosomal Dominant Hypocalcemia Type 2 (ADH2). J Bone Miner Res. 2016; 31: 1207–14. [4] Tenhola et al. Impaired Growth and Intracranial Calcifications in Autosomal Dominant Hypocalcemia Caused by a GNA11 Mutation. Eur J Endocrinol. 2016; 175: 211–8.

scholarly journals Activating Mutations of the G-protein Subunit α 11 Interdomain Interface Cause Autosomal Dominant Hypocalcemia Type 2

2019 ◽  
Vol 105 (3) ◽  
pp. 952-963
Author(s):  
Caroline M Gorvin ◽  
Victoria J Stokes ◽  
Hannah Boon ◽  
Treena Cranston ◽  
Anna K Glück ◽  
...  
Keyword(s):  
G Protein ◽  
Autosomal Dominant ◽  
Hek293 Cells ◽  
Dependent Manner ◽  
Protein Subunit ◽  
Gain Of Function ◽  
Activating Mutations ◽  
Calcium Sensing ◽  
Guanine Nucleotide Binding ◽  
Autosomal Dominant Hypocalcemia

Abstract Context Autosomal dominant hypocalcemia types 1 and 2 (ADH1 and ADH2) are caused by germline gain-of-function mutations of the calcium-sensing receptor (CaSR) and its signaling partner, the G-protein subunit α 11 (Gα 11), respectively. More than 70 different gain-of-function CaSR mutations, but only 6 different gain-of-function Gα 11 mutations are reported to date. Methods We ascertained 2 additional ADH families and investigated them for CaSR and Gα 11 mutations. The effects of identified variants on CaSR signaling were evaluated by transiently transfecting wild-type (WT) and variant expression constructs into HEK293 cells stably expressing CaSR (HEK-CaSR), and measuring intracellular calcium (Ca2+i) and MAPK responses following stimulation with extracellular calcium (Ca2+e). Results CaSR variants were not found, but 2 novel heterozygous germline Gα 11 variants, p.Gly66Ser and p.Arg149His, were identified. Homology modeling of these revealed that the Gly66 and Arg149 residues are located at the interface between the Gα 11 helical and GTPase domains, which is involved in guanine nucleotide binding, and this is the site of 3 other reported ADH2 mutations. The Ca2+i and MAPK responses of cells expressing the variant Ser66 or His149 Gα 11 proteins were similar to WT cells at low Ca2+e, but significantly increased in a dose-dependent manner following Ca2+e stimulation, thereby indicating that the p.Gly66Ser and p.Arg149His variants represent pathogenic gain-of-function Gα 11 mutations. Treatment of Ser66- and His149-Gα 11 expressing cells with the CaSR negative allosteric modulator NPS 2143 normalized Ca2+i and MAPK responses. Conclusion Two novel ADH2-causing mutations that highlight the Gα 11 interdomain interface as a hotspot for gain-of-function Gα 11 mutations have been identified.

The calcilytic NPS2143 rectifies the gain-of-function associated with G-protein [alpha] 11 mutations causing autosomal dominant hypocalcaemia type 2

2014 ◽  
Author(s):  
Valerie Babinsky ◽  
Fadil Hannan ◽  
M Andrew Nesbit ◽  
Sarah Howles ◽  
Jianxin Hu ◽  
...  
Keyword(s):  
G Protein ◽  
Autosomal Dominant ◽  
Gain Of Function

Autosomal dominant hypocalcemia type 2 is caused by germline GNA11 gain-of-function mutations

2013 ◽  
pp. 1-1
Author(s):  
Sarah Howles ◽  
Andrew Nesbit ◽  
Fadil Hannan ◽  
Valerie Babinsky ◽  
Rosie Head ◽  
...  
Keyword(s):  
Autosomal Dominant ◽  
Gain Of Function ◽  
Autosomal Dominant Hypocalcemia

scholarly journals Disorders of the calcium-sensing receptor and partner proteins: insights into the molecular basis of calcium homeostasis

2016 ◽  
Vol 57 (3) ◽  
pp. R127-R142 ◽  
Author(s):  
Fadil M Hannan ◽  
Valerie N Babinsky ◽  
Rajesh V Thakker
Keyword(s):  
G Protein ◽  
Hormone Secretion ◽  
Urinary Calcium ◽  
Calcium Excretion ◽  
Loss Of Function ◽  
Mineral Density ◽  
Gain Of Function ◽  
Type 3

The extracellular calcium (Ca2+o)-sensing receptor (CaSR) is a family C G protein-coupled receptor, which detects alterations in Ca2+o concentrations and modulates parathyroid hormone secretion and urinary calcium excretion. The central role of the CaSR in Ca2+o homeostasis has been highlighted by the identification of mutations affecting the CASR gene on chromosome 3q21.1. Loss-of-function CASR mutations cause familial hypocalciuric hypercalcaemia (FHH), whereas gain-of-function mutations lead to autosomal dominant hypocalcaemia (ADH). However, CASR mutations are only detected in ≤70% of FHH and ADH cases, referred to as FHH type 1 and ADH type 1, respectively, and studies in other FHH and ADH kindreds have revealed these disorders to be genetically heterogeneous. Thus, loss- and gain-of-function mutations of the GNA11 gene on chromosome 19p13.3, which encodes the G-protein α-11 (Gα11) subunit, lead to FHH type 2 and ADH type 2, respectively; whilst loss-of-function mutations of AP2S1 on chromosome 19q13.3, which encodes the adaptor-related protein complex 2 sigma (AP2σ) subunit, cause FHH type 3. These studies have demonstrated Gα11 to be a key mediator of downstream CaSR signal transduction, and also revealed a role for AP2σ, which is involved in clathrin-mediated endocytosis, in CaSR signalling and trafficking. Moreover, FHH type 3 has been demonstrated to represent a more severe FHH variant that may lead to symptomatic hypercalcaemia, low bone mineral density and cognitive dysfunction. In addition, calcimimetic and calcilytic drugs, which are positive and negative CaSR allosteric modulators, respectively, have been shown to be of potential benefit for these FHH and ADH disorders.

scholarly journals Endocrine regulation of G-protein subunit production in an animal model of type 2 diabetes mellitus

2001 ◽  
Vol 168 (3) ◽  
pp. 509-515 ◽  
Author(s):  
BD Rodgers ◽  
M Bernier ◽  
MA Levine
Keyword(s):  
Diabetes Mellitus ◽  
Insulin Resistance ◽  
Type 2 Diabetes ◽  
Animal Model ◽  
Type 2 Diabetes Mellitus ◽  
Animal Models ◽  
G Protein ◽  
Dependent Manner ◽  
Protein Subunit

Adipocyte beta-adrenergic sensitivity is compromised in animal models of obesity and type 2 diabetes. Although changes in the membrane concentrations of G-protein alpha subunits (Galpha) have been implicated, it remains to be determined how these changes are affected by insulin resistance in the different animal models. Because previous studies used young animals, we measured the concentrations of Galpha and Gbeta subunits in epididymal fat from aged (48 weeks old) db/db mice and from their lean littermates to more closely reproduce the model of type 2 diabetes mellitus. Levels of immunoreactive Galphas, Galphai(1/2), Galphao and Galphaq/11 were all significantly greater in adipocyte membranes from the db/db mice than in membranes from their lean non-diabetic littermate controls. Levels of Galphai(1) and Galphai(2) were also individually determined and although they appeared to be slightly higher in db/db membranes, these differences were not significant. Although the levels of both Galphas isoforms were elevated, levels of the 42 and 46 kDa proteins rose by approximately 42% and 20% respectively, indicating differential protein processing of Galphas. By contrast, levels of Galphai3 were similar in the two groups. The levels of common Gbeta and Gbeta2 were also elevated in db/db mice, whereas Gbeta1 and Gbeta4 levels were not different. To determine whether these changes were due to insulin resistance per se or to elevated glucocorticoid production, G-protein subunit levels were quantified in whole cell lysates from 3T3-L1 adipocytes that were stimulated with different concentrations of either insulin or corticosterone. Although none of the subunit levels was affected by insulin, the levels of both Galphas isoforms were increased equally by corticosterone in a concentration-dependent manner. Since glucocorticoids are known regulators of Galphas gene expression in many cell types and in adipocytes from diabetic rodents, the results presented herein appear to more accurately reflect diabetic pathophysiology than do those of previous studies which report a decrease in Galphas levels. Taken together, these results indicate that most of the selective changes in G-protein subunit production in adipocytes from this animal model of type 2 diabetes may not be due to diminished insulin sensitivity, but may be due to other endocrine or metabolic abnormalities associated with the diabetic phenotype.

scholarly journals Intractable Generalized Epilepsy and Autosomal Dominant Hypocalcemia: A Case Report

2019 ◽  
Vol 6 ◽  
pp. 2329048X1987619
Author(s):  
Gian C. Rossi ◽  
Amy L. Patterson ◽  
Amy L. McGregor ◽  
James W. Wheless
Keyword(s):  
Autosomal Dominant ◽  
Receptor Gene ◽  
Behavior Disorder ◽  
Epilepsy Syndrome ◽  
Calcium Sensing Receptor ◽  
Gain Of Function ◽  
Calcium Sensing ◽  
Epileptiform Discharges ◽  
Generalized Epilepsy ◽  
Autosomal Dominant Hypocalcemia

Calcium-sensing receptor gain-of-function mutations are known to cause autosomal dominant hypocalcemia and independently an epilepsy syndrome. We report the unique case of a child with both intractable generalized epilepsy and a chronic abnormality in calcium homeostasis due to a calcium-sensing receptor gene mutation. She is a 16-year-old female who began having staring events around 3 years of age. After her first generalized convulsion at age 5 years, investigations revealed hypocalcemia, hypercalciuria, and central nervous system calcifications. Her electroencephalogram demonstrated generalized epileptiform discharges, a hyperventilation-induced electroclinical seizure, and a photoconvulsive response. She has since been diagnosed with intellectual impairment, behavior disorder, and intractable childhood-onset seizures, the latter of which include eyelid myoclonia with absences. We conclude that calcium-sensing receptor gain-of-function mutations may precipitate an intractable generalized epilepsy syndrome with a comorbid endocrinopathy and that further investigations should be pursued in children with seizures presumed to be provoked by hypocalcemia.

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