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Nesbit MA, Hannan FM, Howles SA, Babinsky VN, Head RA, Cranston T, Rust N, Hobbs MR, Heath H, Thakker RV. Mutations affecting G-protein subunit α11 in hypercalcemia and hypocalcemia. N Engl J Med 2013; 368:2476-2486. [PMID: 23802516 PMCID: PMC3773604 DOI: 10.1056/nejmoa1300253] [Citation(s) in RCA: 227] [Impact Index Per Article: 20.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
BACKGROUND Familial hypocalciuric hypercalcemia is a genetically heterogeneous disorder with three variants: types 1, 2, and 3. Type 1 is due to loss-of-function mutations of the calcium-sensing receptor, a guanine nucleotide-binding protein (G-protein)-coupled receptor that signals through the G-protein subunit α11 (Gα11). Type 3 is associated with adaptor-related protein complex 2, sigma 1 subunit (AP2S1) mutations, which result in altered calcium-sensing receptor endocytosis. We hypothesized that type 2 is due to mutations effecting Gα11 loss of function, since Gα11 is involved in calcium-sensing receptor signaling, and its gene (GNA11) and the type 2 locus are colocalized on chromosome 19p13.3. We also postulated that mutations effecting Gα11 gain of function, like the mutations effecting calcium-sensing receptor gain of function that cause autosomal dominant hypocalcemia type 1, may lead to hypocalcemia. METHODS We performed GNA11 mutational analysis in a kindred with familial hypocalciuric hypercalcemia type 2 and in nine unrelated patients with familial hypocalciuric hypercalcemia who did not have mutations in the gene encoding the calcium-sensing receptor (CASR) or AP2S1. We also performed this analysis in eight unrelated patients with hypocalcemia who did not have CASR mutations. In addition, we studied the effects of GNA11 mutations on Gα11 protein structure and calcium-sensing receptor signaling in human embryonic kidney 293 (HEK293) cells. RESULTS The kindred with familial hypocalciuric hypercalcemia type 2 had an in-frame deletion of a conserved Gα11 isoleucine (Ile200del), and one of the nine unrelated patients with familial hypocalciuric hypercalcemia had a missense GNA11 mutation (Leu135Gln). Missense GNA11 mutations (Arg181Gln and Phe341Leu) were detected in two unrelated patients with hypocalcemia; they were therefore identified as having autosomal dominant hypocalcemia type 2. All four GNA11 mutations predicted disrupted protein structures, and assessment on the basis of in vitro expression showed that familial hypocalciuric hypercalcemia type 2-associated mutations decreased the sensitivity of cells expressing calcium-sensing receptors to changes in extracellular calcium concentrations, whereas autosomal dominant hypocalcemia type 2-associated mutations increased cell sensitivity. CONCLUSIONS Gα11 mutants with loss of function cause familial hypocalciuric hypercalcemia type 2, and Gα11 mutants with gain of function cause a clinical disorder designated as autosomal dominant hypocalcemia type 2. (Funded by the United Kingdom Medical Research Council and others.).
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Affiliation(s)
- M Andrew Nesbit
- Academic Endocrine Unit, Nuffield Department of Clinical Medicine (M.A.N., F.M.H., S.A.H., V.N.B., R.A.H., R.V.T.), and Sir William Dunn School of Pathology (N.R.), University of Oxford, and the Oxford Molecular Genetics Laboratory, Churchill Hospital (T.C.) - all in Oxford, United Kingdom; Core Research Facilities, University of Utah, Salt Lake City (M.R.H.); and Indiana University School of Medicine, Indianapolis (H.H.)
| | - Fadil M Hannan
- Academic Endocrine Unit, Nuffield Department of Clinical Medicine (M.A.N., F.M.H., S.A.H., V.N.B., R.A.H., R.V.T.), and Sir William Dunn School of Pathology (N.R.), University of Oxford, and the Oxford Molecular Genetics Laboratory, Churchill Hospital (T.C.) - all in Oxford, United Kingdom; Core Research Facilities, University of Utah, Salt Lake City (M.R.H.); and Indiana University School of Medicine, Indianapolis (H.H.)
| | - Sarah A Howles
- Academic Endocrine Unit, Nuffield Department of Clinical Medicine (M.A.N., F.M.H., S.A.H., V.N.B., R.A.H., R.V.T.), and Sir William Dunn School of Pathology (N.R.), University of Oxford, and the Oxford Molecular Genetics Laboratory, Churchill Hospital (T.C.) - all in Oxford, United Kingdom; Core Research Facilities, University of Utah, Salt Lake City (M.R.H.); and Indiana University School of Medicine, Indianapolis (H.H.)
| | - Valerie N Babinsky
- Academic Endocrine Unit, Nuffield Department of Clinical Medicine (M.A.N., F.M.H., S.A.H., V.N.B., R.A.H., R.V.T.), and Sir William Dunn School of Pathology (N.R.), University of Oxford, and the Oxford Molecular Genetics Laboratory, Churchill Hospital (T.C.) - all in Oxford, United Kingdom; Core Research Facilities, University of Utah, Salt Lake City (M.R.H.); and Indiana University School of Medicine, Indianapolis (H.H.)
| | - Rosie A Head
- Academic Endocrine Unit, Nuffield Department of Clinical Medicine (M.A.N., F.M.H., S.A.H., V.N.B., R.A.H., R.V.T.), and Sir William Dunn School of Pathology (N.R.), University of Oxford, and the Oxford Molecular Genetics Laboratory, Churchill Hospital (T.C.) - all in Oxford, United Kingdom; Core Research Facilities, University of Utah, Salt Lake City (M.R.H.); and Indiana University School of Medicine, Indianapolis (H.H.)
| | - Treena Cranston
- Academic Endocrine Unit, Nuffield Department of Clinical Medicine (M.A.N., F.M.H., S.A.H., V.N.B., R.A.H., R.V.T.), and Sir William Dunn School of Pathology (N.R.), University of Oxford, and the Oxford Molecular Genetics Laboratory, Churchill Hospital (T.C.) - all in Oxford, United Kingdom; Core Research Facilities, University of Utah, Salt Lake City (M.R.H.); and Indiana University School of Medicine, Indianapolis (H.H.)
| | - Nigel Rust
- Academic Endocrine Unit, Nuffield Department of Clinical Medicine (M.A.N., F.M.H., S.A.H., V.N.B., R.A.H., R.V.T.), and Sir William Dunn School of Pathology (N.R.), University of Oxford, and the Oxford Molecular Genetics Laboratory, Churchill Hospital (T.C.) - all in Oxford, United Kingdom; Core Research Facilities, University of Utah, Salt Lake City (M.R.H.); and Indiana University School of Medicine, Indianapolis (H.H.)
| | - Maurine R Hobbs
- Academic Endocrine Unit, Nuffield Department of Clinical Medicine (M.A.N., F.M.H., S.A.H., V.N.B., R.A.H., R.V.T.), and Sir William Dunn School of Pathology (N.R.), University of Oxford, and the Oxford Molecular Genetics Laboratory, Churchill Hospital (T.C.) - all in Oxford, United Kingdom; Core Research Facilities, University of Utah, Salt Lake City (M.R.H.); and Indiana University School of Medicine, Indianapolis (H.H.)
| | - Hunter Heath
- Academic Endocrine Unit, Nuffield Department of Clinical Medicine (M.A.N., F.M.H., S.A.H., V.N.B., R.A.H., R.V.T.), and Sir William Dunn School of Pathology (N.R.), University of Oxford, and the Oxford Molecular Genetics Laboratory, Churchill Hospital (T.C.) - all in Oxford, United Kingdom; Core Research Facilities, University of Utah, Salt Lake City (M.R.H.); and Indiana University School of Medicine, Indianapolis (H.H.)
| | - Rajesh V Thakker
- Academic Endocrine Unit, Nuffield Department of Clinical Medicine (M.A.N., F.M.H., S.A.H., V.N.B., R.A.H., R.V.T.), and Sir William Dunn School of Pathology (N.R.), University of Oxford, and the Oxford Molecular Genetics Laboratory, Churchill Hospital (T.C.) - all in Oxford, United Kingdom; Core Research Facilities, University of Utah, Salt Lake City (M.R.H.); and Indiana University School of Medicine, Indianapolis (H.H.)
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Raimondi F, Portella G, Orozco M, Fanelli F. Nucleotide binding switches the information flow in ras GTPases. PLoS Comput Biol 2011; 7:e1001098. [PMID: 21390270 PMCID: PMC3048383 DOI: 10.1371/journal.pcbi.1001098] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2010] [Accepted: 01/28/2011] [Indexed: 12/12/2022] Open
Abstract
The Ras superfamily comprises many guanine nucleotide-binding proteins (G proteins) that are essential to intracellular signal transduction. The guanine nucleotide-dependent intrinsic flexibility patterns of five G proteins were investigated in atomic detail through Molecular Dynamics simulations of the GDP- and GTP-bound states (SGDP and SGTP, respectively). For all the considered systems, the intrinsic flexibility of SGDP was higher than that of SGTP, suggesting that Guanine Exchange Factor (GEF) recognition and nucleotide switch require higher amplitude motions than effector recognition or GTP hydrolysis. Functional mode, dynamic domain, and interaction energy correlation analyses highlighted significant differences in the dynamics of small G proteins and Gα proteins, especially in the inactive state. Indeed, SGDP of Gαt, is characterized by a more extensive energy coupling between nucleotide binding site and distal regions involved in GEF recognition compared to small G proteins, which attenuates in the active state. Moreover, mechanically distinct domains implicated in nucleotide switch could be detected in the presence of GDP but not in the presence of GTP. Finally, in small G proteins, functional modes are more detectable in the inactive state than in the active one and involve changes in solvent exposure of two highly conserved amino acids in switches I and II involved in GEF recognition. The average solvent exposure of these amino acids correlates in turn with the rate of GDP release, suggesting for them either direct or indirect roles in the process of nucleotide switch. Collectively, nucleotide binding changes the information flow through the conserved Ras-like domain, where GDP enhances the flexibility of mechanically distinct portions involved in nucleotide switch, and favors long distance allosteric communication (in Gα proteins), compared to GTP. The Ras superfamily comprises many guanine nucleotide-binding proteins (G proteins) that are essential to intracellular signal transduction. These proteins act biologically as molecular switches cycling between ON and OFF states, thereby controlling a variety of processes ranging from cell growth and differentiation to vesicular and nuclear transport. In spite of the extremely high biological and medical relevance of the Ras GTPase superfamily, a comprehensive structural/dynamic view of the trans-family and family-specific functioning mechanisms is still lacking. In this study, we gained insights into the functional dynamics of Ras GTPases by deciphering the dynamic information encrypted in the topology of these proteins depending on the nucleotide-bound state, i.e. GDP- or GTP-bound (SGDP and SGTP, respectively). Collectively, nucleotide binding changes the information flow through the conserved Ras-like domain, where GDP enhances the flexibility of mechanically distinct portions involved in nucleotide switch, and favors long distance allosteric communication (in Gα proteins), compared to GTP. Functional dynamics is instrumental in GDP switch, which for the members of the Gα family, different from small G proteins, requires allosteric communication between nucleotide and Guanine Exchange Factor binding sites.
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Affiliation(s)
- Francesco Raimondi
- Department of Chemistry, University of Modena and Reggio Emilia, Modena, Italy
- Dulbecco Telethon Institute (DTI), University of Modena and Reggio Emilia, Modena, Italy
| | - Guillem Portella
- Molecular Modeling and Bioinformatics Unit, IRB-BSC Joint Research Program in Computational Biology, Institute for Research in Biomedicine, and Barcelona Supercomputing Center, Barcelona, Spain
| | - Modesto Orozco
- Molecular Modeling and Bioinformatics Unit, IRB-BSC Joint Research Program in Computational Biology, Institute for Research in Biomedicine, and Barcelona Supercomputing Center, Barcelona, Spain
- National Institute of Bioinformatics, Parc Científic de Barcelona, Barcelona, Spain
| | - Francesca Fanelli
- Department of Chemistry, University of Modena and Reggio Emilia, Modena, Italy
- Dulbecco Telethon Institute (DTI), University of Modena and Reggio Emilia, Modena, Italy
- * E-mail:
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Hinrichs MV, Montecino M, Bunster M, Olate J. Mutation of the highly conserved Arg165 and Glu168 residues of human Gsalpha disrupts the alphaD-alphaE loop and enhances basal GDP/GTP exchange rate. J Cell Biochem 2005; 93:409-17. [PMID: 15368366 DOI: 10.1002/jcb.20193] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
G protein signalling regulates a wide range of cellular processes such as motility, differentiation, secretion, neurotransmission, and cell division. G proteins consist of three subunits organized as a Galpha monomer associated with a Gbetagamma heterodimer. Structural studies have shown that Galpha subunits are constituted by two domains: a Ras-like domain, also called the GTPase domain (GTPaseD), and an helical domain (HD), which is unique to heterotrimeric G-proteins. The HD display significantly higher primary structure diversity than the GTPaseD. Regardless of this diversity, there are small regions of the HD which show high degree of identity with residues that are 100% conserved. One of such regions is the alpha helixD-alpha helixE loop (alphaD-alphaE) in the HD, which contains the consensus aminoacid sequence R*-[RSA]-[RSAN]-E*-[YF]-[QH]-L in all mammalian Galpha subunits. Interestingly, the highly conserved arginine (R*) and glutamic acid (E*) residues form a salt bridge that stabilizes the alphaD-alphaE loop, that is localized in the top of the cleft formed between the GTPaseD and HD. Because the guanine nucleotide binding site is deeply buried in this cleft and those interdomain interactions are playing an important role in regulating the basal GDP/GTP nucleotide exchange rate of Galpha subunits, we studied the role of these highly conserved R and E residues in Galpha function. In the present study, we mutated the human Gsalpha R165 and E168 residues to alanine (A), thus generating the R165--> A, E168--> A, and R165/E168--> A mutants. We expressed these human Gsalpha (hGsalpha) mutants in bacteria as histidine tagged proteins, purified them by niquel-agarose chromatography and studied their nucleotide exchange properties. We show that the double R165/E168--> A mutant exhibited a fivefold increased GTP binding kinetics, a higher GDP dissociation rate, and an augmented capacity to activate adenylyl cyclase. Structure analysis showed that disruption of the salt bridge between R165 and E168 by the introduced mutations, caused important structural changes in the HD at the alphaD-alphaE loop (residues 160-175) and in the GTPaseD at a region required for Gsalpha activation by the receptor (residues 308-315). In addition, other two GTPaseD regions that surround the GTP binding site were also affected.
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Affiliation(s)
- María Victoria Hinrichs
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Biológicas, Universidad de Concepción, Concepción, Chile
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