1
|
Biasi A, Marino V, Dal Cortivo G, Dell'Orco D. Supramolecular complexes of GCAP1: implications for inherited retinal dystrophies. Int J Biol Macromol 2024; 279:135068. [PMID: 39187109 DOI: 10.1016/j.ijbiomac.2024.135068] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2024] [Revised: 08/16/2024] [Accepted: 08/23/2024] [Indexed: 08/28/2024]
Abstract
Guanylate Cyclase Activating Protein 1 (GCAP1) is a calcium sensor that regulates the enzymatic activity of retinal Guanylate Cyclase 1 (GC1) in photoreceptors in a Ca2+/Mg2+ dependent manner. While point mutations in GCAP1 have been associated with inherited retinal dystrophies (IRDs), their impact on protein dimerization or on the possible interaction with the potent GC1 inhibitor RD3 (retinal degeneration protein 3) has never been investigated. Here, we integrate exhaustive in silico investigations with biochemical assays to evaluate the effects of the p.(E111V) substitution, associated with a severe form of IRD, on GCAP1 homo- and hetero-dimerization, and demonstrate that wild type (WT) GCAP1 directly interacts with RD3. Although inducing constitutive activation in GC1, the E111V substitution only slightly affects the dimerization of GCAP1. Both WT- and E111V-GCAP1 are predominantly monomeric in the absence of the GC1 target, however E111V-GCAP1 shows a stronger tendency to be monomeric in the Ca2+-bound form, corresponding to GC1 inhibiting state. Reconstitution experiments performed in the co-presence of WT-GCAP1, E111V-GCAP1 and RD3 restored nearly physiological regulation of the GC1 enzymatic activity in terms of cGMP synthesis and Ca2+-sensitivity, suggesting new scenarios for biologics-mediated treatment of GCAP1-associated IRDs.
Collapse
Affiliation(s)
- Amedeo Biasi
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, 37134 Verona, Italy
| | - Valerio Marino
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, 37134 Verona, Italy
| | - Giuditta Dal Cortivo
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, 37134 Verona, Italy
| | - Daniele Dell'Orco
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, 37134 Verona, Italy.
| |
Collapse
|
2
|
Asteriti S, Marino V, Avesani A, Biasi A, Dal Cortivo G, Cangiano L, Dell'Orco D. Recombinant protein delivery enables modulation of the phototransduction cascade in mouse retina. Cell Mol Life Sci 2023; 80:371. [PMID: 38001384 PMCID: PMC10673981 DOI: 10.1007/s00018-023-05022-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2023] [Revised: 10/10/2023] [Accepted: 10/27/2023] [Indexed: 11/26/2023]
Abstract
Inherited retinal dystrophies are often associated with mutations in the genes involved in the phototransduction cascade in photoreceptors, a paradigmatic signaling pathway mediated by G protein-coupled receptors. Photoreceptor viability is strictly dependent on the levels of the second messengers cGMP and Ca2+. Here we explored the possibility of modulating the phototransduction cascade in mouse rods using direct or liposome-mediated administration of a recombinant protein crucial for regulating the interplay of the second messengers in photoreceptor outer segments. The effects of administration of the free and liposome-encapsulated human guanylate cyclase-activating protein 1 (GCAP1) were compared in biological systems of increasing complexity (in cyto, ex vivo, and in vivo). The analysis of protein biodistribution and the direct measurement of functional alteration in rod photoresponses show that the exogenous GCAP1 protein is fully incorporated into the mouse retina and photoreceptor outer segments. Furthermore, only in the presence of a point mutation associated with cone-rod dystrophy in humans p.(E111V), protein delivery induces a disease-like electrophysiological phenotype, consistent with constitutive activation of the retinal guanylate cyclase. Our study demonstrates that both direct and liposome-mediated protein delivery are powerful complementary tools for targeting signaling cascades in neuronal cells, which could be particularly important for the treatment of autosomal dominant genetic diseases.
Collapse
Affiliation(s)
- Sabrina Asteriti
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, 37134, Verona, Italy
- Department of Translational Research, University of Pisa, 56123, Pisa, Italy
| | - Valerio Marino
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, 37134, Verona, Italy
| | - Anna Avesani
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, 37134, Verona, Italy
| | - Amedeo Biasi
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, 37134, Verona, Italy
| | - Giuditta Dal Cortivo
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, 37134, Verona, Italy
| | - Lorenzo Cangiano
- Department of Translational Research, University of Pisa, 56123, Pisa, Italy.
| | - Daniele Dell'Orco
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, 37134, Verona, Italy.
| |
Collapse
|
3
|
Sora V, Tiberti M, Beltrame L, Dogan D, Robbani SM, Rubin J, Papaleo E. PyInteraph2 and PyInKnife2 to Analyze Networks in Protein Structural Ensembles. J Chem Inf Model 2023; 63:4237-4245. [PMID: 37437128 DOI: 10.1021/acs.jcim.3c00574] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/14/2023]
Abstract
Due to the complex nature of noncovalent interactions and their long-range effects, analyzing protein conformations using network theory can be enlightening. Protein Structure Networks (PSNs) provide a convenient formalism to study protein structures in relation to essential properties such as key residues for structural stability, allosteric communication, and the effects of modifications of the protein. PSNs can be defined according to very different principles, and the available tools have limitations in input formats, supported models, and version control. Other outstanding problems are related to the definition of network cutoffs and the assessment of the stability of the network properties. The protein science community could benefit from a common framework to carry out these analyses and make them easier to reproduce, reuse, and evaluate. We here provide two open-source software packages, PyInteraph2 and PyInKnife2, to implement and analyze PSNs in a reproducible and documented manner. PyInteraph2 interfaces with multiple formats for protein ensembles and incorporates different network models with the possibility of integrating them into a macronetwork and performing various downstream analyses, including hubs, connected components, and several other centrality measures, and visualizes the networks or further analyzes them thanks to compatibility with Cytoscape.PyInKnife2 that supports the network models implemented in PyInteraph2. It employs a jackknife resampling approach to estimate the convergence of network properties and streamline the selection of distance cutoffs. We foresee that the modular structure of the code and the supported version control system will promote the transition to a community-driven effort, boost reproducibility, and establish common protocols in the PSN field. As developers, we will guarantee the introduction of new functionalities and maintenance, assistance, and training of new contributors.
Collapse
Affiliation(s)
- Valentina Sora
- Cancer Structural Biology, Danish Cancer Institute, Strandboulevarden 49, 2100 Copenhagen, Denmark
- Cancer Systems Biology, Section of Bioinformatics, Department of Health and Technology, Technical University of Denmark, 2800 Lyngby, Denmark
| | - Matteo Tiberti
- Cancer Structural Biology, Danish Cancer Institute, Strandboulevarden 49, 2100 Copenhagen, Denmark
| | - Ludovica Beltrame
- Cancer Systems Biology, Section of Bioinformatics, Department of Health and Technology, Technical University of Denmark, 2800 Lyngby, Denmark
| | - Deniz Dogan
- Cancer Structural Biology, Danish Cancer Institute, Strandboulevarden 49, 2100 Copenhagen, Denmark
| | - Shahriyar Mahdi Robbani
- Cancer Structural Biology, Danish Cancer Institute, Strandboulevarden 49, 2100 Copenhagen, Denmark
| | - Joshua Rubin
- Cancer Structural Biology, Danish Cancer Institute, Strandboulevarden 49, 2100 Copenhagen, Denmark
| | - Elena Papaleo
- Cancer Structural Biology, Danish Cancer Institute, Strandboulevarden 49, 2100 Copenhagen, Denmark
- Cancer Systems Biology, Section of Bioinformatics, Department of Health and Technology, Technical University of Denmark, 2800 Lyngby, Denmark
| |
Collapse
|
4
|
Avesani A, Bielefeld L, Weisschuh N, Marino V, Mazzola P, Stingl K, Haack TB, Koch KW, Dell’Orco D. Molecular Properties of Human Guanylate Cyclase-Activating Protein 3 (GCAP3) and Its Possible Association with Retinitis Pigmentosa. Int J Mol Sci 2022; 23:ijms23063240. [PMID: 35328663 PMCID: PMC8948881 DOI: 10.3390/ijms23063240] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2022] [Revised: 03/12/2022] [Accepted: 03/15/2022] [Indexed: 11/17/2022] Open
Abstract
The cone-specific guanylate cyclase-activating protein 3 (GCAP3), encoded by the GUCA1C gene, has been shown to regulate the enzymatic activity of membrane-bound guanylate cyclases (GCs) in bovine and teleost fish photoreceptors, to an extent comparable to that of the paralog protein GCAP1. To date, the molecular mechanisms underlying GCAP3 function remain largely unexplored. In this work, we report a thorough characterization of the biochemical and biophysical properties of human GCAP3, moreover, we identified an isolated case of retinitis pigmentosa, in which a patient carried the c.301G>C mutation in GUCA1C, resulting in the substitution of a highly conserved aspartate residue by a histidine (p.(D101H)). We found that myristoylated GCAP3 can activate GC1 with a similar Ca2+-dependent profile, but significantly less efficiently than GCAP1. The non-myristoylated form did not induce appreciable regulation of GC1, nor did the p.D101H variant. GCAP3 forms dimers under physiological conditions, but at odds with its paralogs, it tends to form temperature-dependent aggregates driven by hydrophobic interactions. The peculiar properties of GCAP3 were confirmed by 2 ms molecular dynamics simulations, which for the p.D101H variant highlighted a very high structural flexibility and a clear tendency to lose the binding of a Ca2+ ion to EF3. Overall, our data show that GCAP3 has unusual biochemical properties, which make the protein significantly different from GCAP1 and GCAP2. Moreover, the newly identified point mutation resulting in a substantially unfunctional protein could trigger retinitis pigmentosa through a currently unknown mechanism.
Collapse
Affiliation(s)
- Anna Avesani
- Section of Biological Chemistry, Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, 37134 Verona, Italy; (A.A.); (V.M.)
| | - Laura Bielefeld
- Division of Biochemistry, Department of Neuroscience, University of Oldenburg, 26111 Oldenburg, Germany; (L.B.); (K.-W.K.)
| | - Nicole Weisschuh
- Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tübingen, 72076 Tübingen, Germany;
| | - Valerio Marino
- Section of Biological Chemistry, Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, 37134 Verona, Italy; (A.A.); (V.M.)
| | - Pascale Mazzola
- Institute of Medical Genetics and Applied Genomics, University of Tübingen, 72076 Tübingen, Germany; (P.M.); (T.B.H.)
| | - Katarina Stingl
- University Eye Hospital, Centre for Ophthalmology, University of Tübingen, 72076 Tübingen, Germany;
| | - Tobias B. Haack
- Institute of Medical Genetics and Applied Genomics, University of Tübingen, 72076 Tübingen, Germany; (P.M.); (T.B.H.)
- Centre for Rare Diseases, University of Tübingen, 72076 Tübingen, Germany
| | - Karl-Wilhelm Koch
- Division of Biochemistry, Department of Neuroscience, University of Oldenburg, 26111 Oldenburg, Germany; (L.B.); (K.-W.K.)
| | - Daniele Dell’Orco
- Section of Biological Chemistry, Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, 37134 Verona, Italy; (A.A.); (V.M.)
- Correspondence: ; Tel.: +39-045-802-7637
| |
Collapse
|
5
|
Biasi A, Marino V, Dal Cortivo G, Maltese PE, Modarelli AM, Bertelli M, Colombo L, Dell’Orco D. A Novel GUCA1A Variant Associated with Cone Dystrophy Alters cGMP Signaling in Photoreceptors by Strongly Interacting with and Hyperactivating Retinal Guanylate Cyclase. Int J Mol Sci 2021; 22:ijms221910809. [PMID: 34639157 PMCID: PMC8509414 DOI: 10.3390/ijms221910809] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2021] [Revised: 09/30/2021] [Accepted: 10/04/2021] [Indexed: 11/19/2022] Open
Abstract
Guanylate cyclase-activating protein 1 (GCAP1), encoded by the GUCA1A gene, is a neuronal calcium sensor protein involved in shaping the photoresponse kinetics in cones and rods. GCAP1 accelerates or slows the cGMP synthesis operated by retinal guanylate cyclase (GC) based on the light-dependent levels of intracellular Ca2+, thereby ensuring a timely regulation of the phototransduction cascade. We found a novel variant of GUCA1A in a patient affected by autosomal dominant cone dystrophy (adCOD), leading to the Asn104His (N104H) amino acid substitution at the protein level. While biochemical analysis of the recombinant protein showed impaired Ca2+ sensitivity of the variant, structural properties investigated by circular dichroism and limited proteolysis excluded major structural rearrangements induced by the mutation. Analytical gel filtration profiles and dynamic light scattering were compatible with a dimeric protein both in the presence of Mg2+ alone and Mg2+ and Ca2+. Enzymatic assays showed that N104H-GCAP1 strongly interacts with the GC, with an affinity that doubles that of the WT. The doubled IC50 value of the novel variant (520 nM for N104H vs. 260 nM for the WT) is compatible with a constitutive activity of GC at physiological levels of Ca2+. The structural region at the interface with the GC may acquire enhanced flexibility under high Ca2+ conditions, as suggested by 2 μs molecular dynamics simulations. The altered interaction with GC would cause hyper-activity of the enzyme at both low and high Ca2+ levels, which would ultimately lead to toxic accumulation of cGMP and Ca2+ in the photoreceptor outer segment, thus triggering cell death.
Collapse
Affiliation(s)
- Amedeo Biasi
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, 37134 Verona, Italy; (A.B.); (V.M.); (G.D.C.)
| | - Valerio Marino
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, 37134 Verona, Italy; (A.B.); (V.M.); (G.D.C.)
| | - Giuditta Dal Cortivo
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, 37134 Verona, Italy; (A.B.); (V.M.); (G.D.C.)
| | | | - Antonio Mattia Modarelli
- Department of Ophthalmology, ASST Santi Paolo e Carlo Hospital, University of Milan, 20142 Milano, Italy;
| | - Matteo Bertelli
- MAGI’S Lab s.r.l., 38068 Rovereto, Italy; (P.E.M.); (M.B.)
- MAGI Euregio, 39100 Bolzano, Italy
| | - Leonardo Colombo
- Department of Ophthalmology, ASST Santi Paolo e Carlo Hospital, University of Milan, 20142 Milano, Italy;
- Correspondence: (L.C.); (D.D.); Tel.: +39-02-81844301 (L.C.); +39-045-802-7637 (D.D.)
| | - Daniele Dell’Orco
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, 37134 Verona, Italy; (A.B.); (V.M.); (G.D.C.)
- Correspondence: (L.C.); (D.D.); Tel.: +39-02-81844301 (L.C.); +39-045-802-7637 (D.D.)
| |
Collapse
|
6
|
Marino V, Dal Cortivo G, Maltese PE, Placidi G, De Siena E, Falsini B, Bertelli M, Dell’Orco D. Impaired Ca 2+ Sensitivity of a Novel GCAP1 Variant Causes Cone Dystrophy and Leads to Abnormal Synaptic Transmission Between Photoreceptors and Bipolar Cells. Int J Mol Sci 2021; 22:ijms22084030. [PMID: 33919796 PMCID: PMC8070792 DOI: 10.3390/ijms22084030] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2021] [Revised: 04/06/2021] [Accepted: 04/09/2021] [Indexed: 01/23/2023] Open
Abstract
Guanylate cyclase-activating protein 1 (GCAP1) is involved in the shutdown of the phototransduction cascade by regulating the enzymatic activity of retinal guanylate cyclase via a Ca2+/cGMP negative feedback. While the phototransduction-associated role of GCAP1 in the photoreceptor outer segment is widely established, its implication in synaptic transmission to downstream neurons remains to be clarified. Here, we present clinical and biochemical data on a novel isolate GCAP1 variant leading to a double amino acid substitution (p.N104K and p.G105R) and associated with cone dystrophy (COD) with an unusual phenotype. Severe alterations of the electroretinogram were observed under both scotopic and photopic conditions, with a negative pattern and abnormally attenuated b-wave component. The biochemical and biophysical analysis of the heterologously expressed N104K-G105R variant corroborated by molecular dynamics simulations highlighted a severely compromised Ca2+-sensitivity, accompanied by minor structural and stability alterations. Such differences reflected on the dysregulation of both guanylate cyclase isoforms (RetGC1 and RetGC2), resulting in the constitutive activation of both enzymes at physiological levels of Ca2+. As observed with other GCAP1-associated COD, perturbation of the homeostasis of Ca2+ and cGMP may lead to the toxic accumulation of second messengers, ultimately triggering cell death. However, the abnormal electroretinogram recorded in this patient also suggested that the dysregulation of the GCAP1–cyclase complex further propagates to the synaptic terminal, thereby altering the ON-pathway related to the b-wave generation. In conclusion, the pathological phenotype may rise from a combination of second messengers’ accumulation and dysfunctional synaptic communication with bipolar cells, whose molecular mechanisms remain to be clarified.
Collapse
Affiliation(s)
- Valerio Marino
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, 37129 Verona, Italy; (V.M.); (G.D.C.)
| | - Giuditta Dal Cortivo
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, 37129 Verona, Italy; (V.M.); (G.D.C.)
| | | | - Giorgio Placidi
- Fondazione Policlinico Universitario “A. Gemelli”, IRCCS, 00168 Rome, Italy; (G.P.); (E.D.S.)
- Università Cattolica del Sacro Cuore, 00168 Rome, Italy
| | - Elisa De Siena
- Fondazione Policlinico Universitario “A. Gemelli”, IRCCS, 00168 Rome, Italy; (G.P.); (E.D.S.)
- Università Cattolica del Sacro Cuore, 00168 Rome, Italy
| | - Benedetto Falsini
- Fondazione Policlinico Universitario “A. Gemelli”, IRCCS, 00168 Rome, Italy; (G.P.); (E.D.S.)
- Università Cattolica del Sacro Cuore, 00168 Rome, Italy
- Correspondence: (B.F.); (D.D.); Tel.: +39-06-3015-6344 (B.F.); +39-045-802-7637 (D.D.)
| | - Matteo Bertelli
- MAGI’S Lab S.R.L., 38068 Rovereto, Italy; (P.E.M.); (M.B.)
- MAGI Euregio, 39100 Bolzano, Italy
| | - Daniele Dell’Orco
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, 37129 Verona, Italy; (V.M.); (G.D.C.)
- Correspondence: (B.F.); (D.D.); Tel.: +39-06-3015-6344 (B.F.); +39-045-802-7637 (D.D.)
| |
Collapse
|
7
|
Avesani A, Marino V, Zanzoni S, Koch KW, Dell'Orco D. Molecular properties of human guanylate cyclase-activating protein 2 (GCAP2) and its retinal dystrophy-associated variant G157R. J Biol Chem 2021; 296:100619. [PMID: 33812995 PMCID: PMC8113879 DOI: 10.1016/j.jbc.2021.100619] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2021] [Revised: 03/25/2021] [Accepted: 03/30/2021] [Indexed: 12/31/2022] Open
Abstract
In murine and bovine photoreceptors, guanylate cyclase-activating protein 2 (GCAP2) activates retinal guanylate cyclases (GCs) at low Ca2+ levels, thus contributing to the Ca2+/cGMP negative feedback on the cyclase together with its paralog guanylate cyclase-activating protein 1, which has the same function but different Ca2+ sensitivity. In humans, a GCAP2 missense mutation (G157R) has been associated with inherited retinal degeneration (IRD) via an unknown molecular mechanism. Here, we characterized the biochemical properties of human GCAP2 and the G157R variant, focusing on its dimerization and the Ca2+/Mg2+-binding processes in the presence or absence of N-terminal myristoylation. We found that human GCAP2 and its bovine/murine orthologs significantly differ in terms of oligomeric properties, cation binding, and GC regulation. Myristoylated GCAP2 endothermically binds up to 3 Mg2+ with high affinity and forms a compact dimer that may reversibly dissociate in the presence of Ca2+. Conversely, nonmyristoylated GCAP2 does not bind Mg2+ over the physiological range and remains as a monomer in the absence of Ca2+. Both myristoylated and nonmyristoylated GCAP2 bind Ca2+ with high affinity. At odds with guanylate cyclase-activating protein 1 and independently of myristoylation, human GCAP2 does not significantly activate retinal GC1 in a Ca2+-dependent fashion. The IRD-associated G157R variant is characterized by a partly misfolded, molten globule-like conformation with reduced affinity for cations and prone to form aggregates, likely mediated by hydrophobic interactions. Our findings suggest that GCAP2 might be mostly implicated in processes other than phototransduction in human photoreceptors and suggest a possible molecular mechanism for G157R-associated IRD.
Collapse
Affiliation(s)
- Anna Avesani
- Department of Neurosciences, Biomedicine and Movement Sciences, Biological Chemistry Section, University of Verona, Verona, Italy
| | - Valerio Marino
- Department of Neurosciences, Biomedicine and Movement Sciences, Biological Chemistry Section, University of Verona, Verona, Italy
| | - Serena Zanzoni
- Centro Piattaforme Tecnologiche, University of Verona, Verona, Italy
| | - Karl-Wilhelm Koch
- Department of Neuroscience, Division of Biochemistry, University of Oldenburg, Oldenburg, Germany
| | - Daniele Dell'Orco
- Department of Neurosciences, Biomedicine and Movement Sciences, Biological Chemistry Section, University of Verona, Verona, Italy.
| |
Collapse
|
8
|
Bonì F, Marino V, Bidoia C, Mastrangelo E, Barbiroli A, Dell’Orco D, Milani M. Modulation of Guanylate Cyclase Activating Protein 1 (GCAP1) Dimeric Assembly by Ca 2+ or Mg 2+: Hints to Understand Protein Activity. Biomolecules 2020; 10:biom10101408. [PMID: 33027977 PMCID: PMC7600425 DOI: 10.3390/biom10101408] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Revised: 09/30/2020] [Accepted: 10/01/2020] [Indexed: 11/16/2022] Open
Abstract
The guanylyl cyclase-activating protein 1, GCAP1, activates or inhibits retinal guanylyl cyclase (retGC) depending on cellular Ca2+ concentrations. Several point mutations of GCAP1 have been associated with impaired calcium sensitivity that eventually triggers progressive retinal degeneration. In this work, we demonstrate that the recombinant human protein presents a highly dynamic monomer-dimer equilibrium, whose dissociation constant is influenced by salt concentration and, more importantly, by protein binding to Ca2+ or Mg2+. Based on small-angle X-ray scattering data, protein-protein docking, and molecular dynamics simulations we propose two novel three-dimensional models of Ca2+-bound GCAP1 dimer. The different propensity of human GCAP1 to dimerize suggests structural differences induced by cation binding potentially involved in the regulation of retGC activity.
Collapse
Affiliation(s)
- Francesco Bonì
- CNR-IBF, Istituto di Biofisica, Via Celoria 26, I-20133 Milan, Italy; (F.B.); (C.B.); (E.M.)
- Dipartimento di Bioscienze, Università di Milano, Via Celoria 26, I-20133 Milan, Italy
| | - Valerio Marino
- Dipartimento di Neuroscienze, Biomedicina e Movimento, Sezione di Chimica Biologica, Università di Verona, I-37134 Verona, Italy;
| | - Carlo Bidoia
- CNR-IBF, Istituto di Biofisica, Via Celoria 26, I-20133 Milan, Italy; (F.B.); (C.B.); (E.M.)
- Dipartimento di Bioscienze, Università di Milano, Via Celoria 26, I-20133 Milan, Italy
| | - Eloise Mastrangelo
- CNR-IBF, Istituto di Biofisica, Via Celoria 26, I-20133 Milan, Italy; (F.B.); (C.B.); (E.M.)
- Dipartimento di Bioscienze, Università di Milano, Via Celoria 26, I-20133 Milan, Italy
| | - Alberto Barbiroli
- Dipartimento di Scienze per gli Alimenti, la Nutrizione e l’Ambiente, Università degli Studi di Milano, Via Celoria 2, I-20133 Milan, Italy;
| | - Daniele Dell’Orco
- Dipartimento di Neuroscienze, Biomedicina e Movimento, Sezione di Chimica Biologica, Università di Verona, I-37134 Verona, Italy;
- Correspondence: (D.D.); (M.M.); Tel.: +39-045-802-7637 (D.D.); +39-02-5031-4890 (M.M.)
| | - Mario Milani
- CNR-IBF, Istituto di Biofisica, Via Celoria 26, I-20133 Milan, Italy; (F.B.); (C.B.); (E.M.)
- Dipartimento di Bioscienze, Università di Milano, Via Celoria 26, I-20133 Milan, Italy
- Correspondence: (D.D.); (M.M.); Tel.: +39-045-802-7637 (D.D.); +39-02-5031-4890 (M.M.)
| |
Collapse
|
9
|
Dal Cortivo G, Marino V, Bonì F, Milani M, Dell'Orco D. Missense mutations affecting Ca 2+-coordination in GCAP1 lead to cone-rod dystrophies by altering protein structural and functional properties. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2020; 1867:118794. [PMID: 32650103 DOI: 10.1016/j.bbamcr.2020.118794] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Revised: 07/01/2020] [Accepted: 07/03/2020] [Indexed: 02/06/2023]
Abstract
Guanylate cyclase activating protein 1 (GCAP1) is a neuronal calcium sensor (NCS) involved in the early biochemical steps underlying the phototransduction cascade. By switching from a Ca2+-bound form in the dark to a Mg2+-bound state following light activation of the cascade, GCAP1 triggers the activation of the retinal guanylate cyclase (GC), thus replenishing the levels of 3',5'-cyclic monophosphate (cGMP) necessary to re-open CNG channels. Here, we investigated the structural and functional effects of three missense mutations in GCAP1 associated with cone-rod dystrophy, which severely perturb the homeostasis of cGMP and Ca2+. Substitutions affect residues directly involved in Ca2+ coordination in either EF3 (D100G) or EF4 (E155A and E155G) Ca2+ binding motifs. We found that all GCAP1 variants form relatively stable dimers showing decreased apparent affinity for Ca2+ and blocking the enzyme in a constitutively active state at physiological levels of Ca2+. Interestingly, by corroborating spectroscopic experiments with molecular dynamics simulations we show that beside local structural effects, mutation of the bidentate glutamate in an EF-hand calcium binding motif can profoundly perturb the flexibility of the adjacent EF-hand as well, ultimately destabilizing the whole domain. Therefore, while Ca2+-binding to GCAP1 per se occurs sequentially, allosteric effects may connect EF hand motifs, which appear to be essential for the integrity of the structural switch mechanism in GCAP1, and perhaps in other NCS proteins.
Collapse
Affiliation(s)
- Giuditta Dal Cortivo
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, I-37134 Verona, Italy
| | - Valerio Marino
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, I-37134 Verona, Italy
| | - Francesco Bonì
- CNR-IBF, Istituto di Biofisica, Via Celoria 26, I-20133 Milano, Italy; Dipartimento di Bioscienze, Università di Milano, Via Celoria 26, I-20133 Milano, Italy
| | - Mario Milani
- CNR-IBF, Istituto di Biofisica, Via Celoria 26, I-20133 Milano, Italy; Dipartimento di Bioscienze, Università di Milano, Via Celoria 26, I-20133 Milano, Italy
| | - Daniele Dell'Orco
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, I-37134 Verona, Italy.
| |
Collapse
|
10
|
Abbas S, Marino V, Weisschuh N, Kieninger S, Solaki M, Dell’Orco D, Koch KW. Neuronal Calcium Sensor GCAP1 Encoded by GUCA1A Exhibits Heterogeneous Functional Properties in Two Cases of Retinitis Pigmentosa. ACS Chem Neurosci 2020; 11:1458-1470. [PMID: 32298085 DOI: 10.1021/acschemneuro.0c00111] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Genetic heterogeneity leading to retinal disorders impairs biological processes by causing, for example, severe disorder of signal transduction in photoreceptor outer segments. A normal balance of the second messenger homeostasis in photoreceptor cells seems to be a crucial factor for healthy and normal photoreceptor function. Genes like GUCY2D coding for guanylate cyclase GC-E and GUCA1A coding for the Ca2+-sensor guanylate cyclase-activating protein GCAP1 are critical for a precisely controlled synthesis of the second messenger cGMP. Mutations in GUCA1A frequently correlate in patients with cone dystrophy and cone-rod dystrophy. Here, we report two mutations in the GUCA1A gene that were found in patients diagnosed with retinitis pigmentosa, a phenotype that was rarely detected among previous cases of GUCA1A related retinopathies. One patient was heterozygous for the missense variant c.55C > T (p.H19Y), while the other patient was heterozygous for the missense variant c.479T > G (p.V160G). Using heterologous expression and cell culture systems, we examined the functional and molecular consequences of these point mutations. Both variants showed a dysregulation of guanylate cyclase activity, either a profound shift in Ca2+-sensitivity (H19Y) or a nearly complete loss of activating potency (V160G). Functional heterogeneity became also apparent in Ca2+/Mg2+-binding properties and protein conformational dynamics. A faster progression of retinal dystrophy in the patient carrying the V160G mutation seems to correlate with the more severe impairment of this variant.
Collapse
Affiliation(s)
- Seher Abbas
- Department of Neuroscience, Division of Biochemistry, University of Oldenburg, 26111 Oldenburg, Germany
| | - Valerio Marino
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, 37134 Verona, Italy
| | - Nicole Weisschuh
- Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tübingen, 72076 Tübingen, Germany
| | - Sinja Kieninger
- Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tübingen, 72076 Tübingen, Germany
| | - Maria Solaki
- Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tübingen, 72076 Tübingen, Germany
| | - Daniele Dell’Orco
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, 37134 Verona, Italy
| | - Karl-Wilhelm Koch
- Department of Neuroscience, Division of Biochemistry, University of Oldenburg, 26111 Oldenburg, Germany
| |
Collapse
|
11
|
Abbas S, Koch KW. Quantitative Determination of Ca 2+-binding to Ca 2+-sensor Proteins by Isothermal Titration Calorimetry. Bio Protoc 2020; 10:e3580. [PMID: 33659550 DOI: 10.21769/bioprotoc.3580] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2019] [Revised: 01/19/2020] [Accepted: 01/21/2020] [Indexed: 01/29/2023] Open
Abstract
Diverse and complex molecular recognitions are central elements of signal transduction cascades. The strength and nature of these interaction modes can be determined by different experimental approaches. Among those, Isothermal titration calorimetry (ITC) offers certain advantages by providing binding constants and thermodynamic parameters from titration series without a need to label or immobilize one or more interaction partners. Furthermore, second messenger homeostasis involving Ca2+-ions requires in particular knowledge about stoichiometries and affinities of Ca2+-binding to Ca2+-sensor proteins or Ca2+-dependent regulators, which can be obtained by employing ITC. We used ITC to measure these parameters for a set of neuronal Ca2+-sensor proteins operating in photoreceptor cells. Here, we present a step wise protocol to (a) measure Ca2+ interaction with the Ca2+-sensor guanylate cyclase-activating protein 1, (b) to design an ITC experiment and prepare samples, (c) to remove Ca2+ nearly completely from Ca2+ binding proteins without using a chelating agent like EGTA.
Collapse
Affiliation(s)
- Seher Abbas
- Department of Neuroscience, Division of Biochemistry, University of Oldenburg, Oldenburg D-26129, Germany
| | - Karl-Wilhelm Koch
- Department of Neuroscience, Division of Biochemistry, University of Oldenburg, Oldenburg D-26129, Germany
| |
Collapse
|
12
|
Constitutive Activation of Guanylate Cyclase by the G86R GCAP1 Variant Is Due to "Locking" Cation-π Interactions that Impair the Activator-to-Inhibitor Structural Transition. Int J Mol Sci 2020; 21:ijms21030752. [PMID: 31979372 PMCID: PMC7037459 DOI: 10.3390/ijms21030752] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2019] [Revised: 01/18/2020] [Accepted: 01/20/2020] [Indexed: 02/06/2023] Open
Abstract
Guanylate Cyclase activating protein 1 (GCAP1) mediates the Ca2+-dependent regulation of the retinal Guanylate Cyclase (GC) in photoreceptors, acting as a target inhibitor at high [Ca2+] and as an activator at low [Ca2+]. Recently, a novel missense mutation (G86R) was found in GUCA1A, the gene encoding for GCAP1, in patients diagnosed with cone-rod dystrophy. The G86R substitution was found to affect the flexibility of the hinge region connecting the N- and C-domains of GCAP1, resulting in decreased Ca2+-sensitivity and abnormally enhanced affinity for GC. Based on a structural model of GCAP1, here, we tested the hypothesis of a cation-π interaction between the positively charged R86 and the aromatic W94 as the main mechanism underlying the impaired activator-to-inhibitor conformational change. W94 was mutated to F or L, thus, resulting in the double mutants G86R+W94L/F. The double mutants showed minor structural and stability changes with respect to the single G86R mutant, as well as lower affinity for both Mg2+ and Ca2+, moreover, substitutions of W94 abolished "phase II" in Ca2+-titrations followed by intrinsic fluorescence. Interestingly, the presence of an aromatic residue in position 94 significantly increased the aggregation propensity of Ca2+-loaded GCAP1 variants. Finally, atomistic simulations of all GCAP1 variants in the presence of Ca2+ supported the presence of two cation-π interactions involving R86, which was found to act as a bridge between W94 and W21, thus, locking the hinge region in an activator-like conformation and resulting in the constitutive activation of the target under physiological conditions.
Collapse
|
13
|
Normal GCAPs partly compensate for altered cGMP signaling in retinal dystrophies associated with mutations in GUCA1A. Sci Rep 2019; 9:20105. [PMID: 31882816 PMCID: PMC6934868 DOI: 10.1038/s41598-019-56606-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2019] [Accepted: 12/12/2019] [Indexed: 01/20/2023] Open
Abstract
Missense mutations in the GUCA1A gene encoding guanylate cyclase-activating protein 1 (GCAP1) are associated with autosomal dominant cone/cone-rod (CORD) dystrophies. The nature of the inheritance pattern implies that a pool of normal GCAP proteins is present in photoreceptors together with the mutated variant. To assess whether human GCAP1 and GCAP2 may similarly regulate the activity of the retinal membrane guanylate cyclase GC-1 (GC-E) in the presence of the recently discovered E111V-GCAP1 CORD-variant, we combined biochemical and in silico assays. Surprisingly, human GCAP2 does not activate GC1 over the physiological range of Ca2+ whereas wild-type GCAP1 significantly attenuates the dysregulation of GC1 induced by E111V-GCAP1. Simulation of the phototransduction cascade in a well-characterized murine system, where GCAP2 is able to activate the GC1, suggests that both GCAPs can act in a synergic manner to mitigate the effects of the CORD-mutation. We propose the existence of a species-dependent compensatory mechanism. In murine photoreceptors, slight increases of wild-type GCAPs levels may significantly attenuate the increase in intracellular Ca2+ and cGMP induced by E111V-GCAP1 in heterozygous conditions. In humans, however, the excess of wild-type GCAP1 may only partly attenuate the mutant-induced dysregulation of cGMP signaling due to the lack of GC1-regulation by GCAP2.
Collapse
|
14
|
Mizobuchi K, Hayashi T, Katagiri S, Yoshitake K, Fujinami K, Yang L, Kuniyoshi K, Shinoda K, Machida S, Kondo M, Ueno S, Terasaki H, Matsuura T, Tsunoda K, Iwata T, Nakano T. Characterization of GUCA1A-associated dominant cone/cone-rod dystrophy: low prevalence among Japanese patients with inherited retinal dystrophies. Sci Rep 2019; 9:16851. [PMID: 31728034 PMCID: PMC6856191 DOI: 10.1038/s41598-019-52660-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Accepted: 10/21/2019] [Indexed: 12/14/2022] Open
Abstract
GUCA1A gene variants are associated with autosomal dominant (AD) cone dystrophy (COD) and cone-rod dystrophy (CORD). GUCA1A-associated AD-COD/CORD has never been reported in the Japanese population. The purpose of this study was to investigate clinical and genetic features of GUCA1A-associated AD-COD/CORD from a large Japanese cohort. We identified 8 variants [c.C50_80del (p.E17VfsX22), c.T124A (p.F42I), c.C204G (p.D68E), c.C238A (p.L80I), c.T295A (p.Y99N), c.A296C (p.Y99S), c.C451T (p.L151F), and c.A551G (p.Q184R)] in 14 families from our whole exome sequencing database composed of 1385 patients with inherited retinal diseases (IRDs) from 1192 families. Three variants (p.Y99N, p.Y99S, and p.L151F), which are located on/around EF-hand domains 3 and 4, were confirmed as "pathogenic", whereas the other five variants, which did not co-segregate with IRDs, were considered "non-pathogenic". Ophthalmic findings of 9 patients from 3 families with the pathogenic variants showed central visual impairment from early to middle-age onset and progressive macular atrophy. Electroretinography revealed severely decreased or non-recordable cone responses, whereas rod responses were highly variable, ranging from nearly normal to non-recordable. Our results indicate that the three pathogenic variants, two of which were novel, underlie AD-COD/CORD with progressive retinal atrophy, and the prevalence (0.25%, 3/1192 families) of GUCA1A-associated IRDs may be low among Japanese patients.
Collapse
Affiliation(s)
- Kei Mizobuchi
- Department of Ophthalmology, The Jikei University School of Medicine, Tokyo, Japan
| | - Takaaki Hayashi
- Department of Ophthalmology, The Jikei University School of Medicine, Tokyo, Japan. .,Department of Ophthalmology, Katsushika Medical Center, The Jikei University School of Medicine, Tokyo, Japan.
| | - Satoshi Katagiri
- Department of Ophthalmology, The Jikei University School of Medicine, Tokyo, Japan
| | - Kazutoshi Yoshitake
- Division of Molecular and Cellular Biology, National Institute of Sensory Organs, National Tokyo Medical Center, Tokyo, Japan
| | - Kaoru Fujinami
- Division of Vision Research, National Institute of Sensory Organs, National Hospital Organization Tokyo Medical Center, Tokyo, Japan.,Department of Ophthalmology, Keio University School of Medicine, Tokyo, Japan.,UCL Institute of Ophthalmology associated with Moorfields Eye Hospital, London, UK
| | - Lizhu Yang
- Division of Vision Research, National Institute of Sensory Organs, National Hospital Organization Tokyo Medical Center, Tokyo, Japan.,Department of Ophthalmology, Keio University School of Medicine, Tokyo, Japan
| | - Kazuki Kuniyoshi
- Department of Ophthalmology, Kindai University Faculty of Medicine, Osaka, Japan
| | - Kei Shinoda
- Department of Ophthalmology, Teikyo University School of Medicine, Tokyo, Japan
| | - Shigeki Machida
- Department of Ophthalmology, Dokkyo Medical University Saitama Medical Center, Saitama, Japan.,Department of Ophthalmology, Iwate Medical University School of Medicine, Iwate, Japan
| | - Mineo Kondo
- Department of Ophthalmology, Mie University Graduate School of Medicine, Mie, Japan
| | - Shinji Ueno
- Department of Ophthalmology, Nagoya University Graduate School of Medicine, Aichi, Japan
| | - Hiroko Terasaki
- Department of Ophthalmology, Nagoya University Graduate School of Medicine, Aichi, Japan
| | - Tomokazu Matsuura
- Department of Laboratory Medicine, The Jikei University School of Medicine, Tokyo, Japan
| | - Kazushige Tsunoda
- Division of Vision Research, National Institute of Sensory Organs, National Hospital Organization Tokyo Medical Center, Tokyo, Japan
| | - Takeshi Iwata
- Division of Molecular and Cellular Biology, National Institute of Sensory Organs, National Tokyo Medical Center, Tokyo, Japan
| | - Tadashi Nakano
- Department of Ophthalmology, The Jikei University School of Medicine, Tokyo, Japan
| |
Collapse
|
15
|
Dal Cortivo G, Marino V, Iacobucci C, Vallone R, Arlt C, Rehkamp A, Sinz A, Dell'Orco D. Oligomeric state, hydrodynamic properties and target recognition of human Calcium and Integrin Binding protein 2 (CIB2). Sci Rep 2019; 9:15058. [PMID: 31636333 PMCID: PMC6803640 DOI: 10.1038/s41598-019-51573-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2019] [Accepted: 09/12/2019] [Indexed: 11/23/2022] Open
Abstract
Calcium- and Integrin-Binding protein 2 (CIB2) is a small and ubiquitously expressed protein with largely unknown biological function but ascertained role in hearing physiology and disease. Recent studies found that CIB2 binds Ca2+ with moderate affinity and dimerizes under conditions mimicking the physiological ones. Here we provided new lines of evidence on CIB2 oligomeric state and the mechanism of interaction with the α7B integrin target. Based on a combination of native mass spectrometry, chemical cross-linking/mass spectrometry, analytical gel filtration, dynamic light scattering and molecular dynamics simulations we conclude that CIB2 is monomeric under all tested conditions and presents uncommon hydrodynamic properties, most likely due to the high content of hydrophobic solvent accessible surface. Surface plasmon resonance shows that the interaction with α7B occurs with relatively low affinity and is limited to the cytosolic region proximal to the membrane, being kinetically favored in the presence of physiological Mg2+ and in the absence of Ca2+. Although CIB2 binds to an α7B peptide in a 1:1 stoichiometry, the formation of the complex might induce binding of another CIB2 molecule.
Collapse
Affiliation(s)
- Giuditta Dal Cortivo
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, Verona, Italy
| | - Valerio Marino
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, Verona, Italy
- Department of Translational Research and New Technologies in Medicine and Surgery, University of Pisa, Pisa, Italy
| | - Claudio Iacobucci
- Department of Pharmaceutical Chemistry and Bioanalytics, Institute of Pharmacy, Charles Tanford Protein Center, Martin Luther University Halle-Wittenberg, Halle, Germany
| | - Rosario Vallone
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, Verona, Italy
- Structural Biology and Biophysics Unit, Fondazione Ri.MED, Palermo, Italy
| | - Christian Arlt
- Department of Pharmaceutical Chemistry and Bioanalytics, Institute of Pharmacy, Charles Tanford Protein Center, Martin Luther University Halle-Wittenberg, Halle, Germany
| | - Anne Rehkamp
- Department of Pharmaceutical Chemistry and Bioanalytics, Institute of Pharmacy, Charles Tanford Protein Center, Martin Luther University Halle-Wittenberg, Halle, Germany
| | - Andrea Sinz
- Department of Pharmaceutical Chemistry and Bioanalytics, Institute of Pharmacy, Charles Tanford Protein Center, Martin Luther University Halle-Wittenberg, Halle, Germany
| | - Daniele Dell'Orco
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, Verona, Italy.
| |
Collapse
|
16
|
Marino V, Dal Cortivo G, Oppici E, Maltese PE, D'Esposito F, Manara E, Ziccardi L, Falsini B, Magli A, Bertelli M, Dell'Orco D. A novel p.(Glu111Val) missense mutation in GUCA1A associated with cone-rod dystrophy leads to impaired calcium sensing and perturbed second messenger homeostasis in photoreceptors. Hum Mol Genet 2019; 27:4204-4217. [PMID: 30184081 DOI: 10.1093/hmg/ddy311] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Accepted: 08/24/2018] [Indexed: 01/09/2023] Open
Abstract
Guanylate Cyclase-Activating Protein 1 (GCAP1) regulates the enzymatic activity of the photoreceptor guanylate cyclases (GC), leading to inhibition or activation of the cyclic guanosine monophosphate (cGMP) synthesis depending on its Ca2+- or Mg2+-loaded state. By genetically screening a family of patients diagnosed with cone-rod dystrophy, we identified a novel missense mutation with autosomal dominant inheritance pattern (c.332A>T; p.(Glu111Val); E111V from now on) in the GUCA1A gene coding for GCAP1. We performed a thorough biochemical and biophysical investigation of wild type (WT) and E111V human GCAP1 by heterologous expression and purification of the recombinant proteins. The E111V substitution disrupts the coordination of the Ca2+ ion in the high-affinity site (EF-hand 3, EF3), thus significantly decreasing the ability of GCAP1 to sense Ca2+ (∼80-fold higher Kdapp compared to WT). Both WT and E111V GCAP1 form dimers independently on the presence of cations, but the E111V Mg2+-bound form is prone to severe aggregation over time. Molecular dynamics simulations suggest a significantly increased flexibility of both the EF3 and EF4 cation binding loops for the Ca2+-bound form of E111V GCAP1, in line with the decreased affinity for Ca2+. In contrast, a more rigid backbone conformation is observed in the Mg2+-bound state compared to the WT, which results in higher thermal stability. Functional assays confirm that E111V GCAP1 interacts with the target GC with a similar apparent affinity (EC50); however, the mutant shifts the GC inhibition out of the physiological [Ca2+] (IC50E111V ∼10 μM), thereby leading to the aberrant constitutive synthesis of cGMP under conditions of dark-adapted photoreceptors.
Collapse
Affiliation(s)
- Valerio Marino
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, Verona, Italy.,Department of Translational Research and of New Surgical and Medical Technologies, University of Pisa, Pisa, Italy
| | - Giuditta Dal Cortivo
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, Verona, Italy
| | - Elisa Oppici
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, Verona, Italy
| | | | - Fabiana D'Esposito
- Imperial College Ophthalmic Research Unit, Western Eye Hospital, Imperial College Healthcare NHS Trust, London, UK.,MAGI Euregio, Bolzano, Italy.,Eye Clinic, Department of Neurosciences, Reproductive Sciences and Dentistry, Federico II University, Naples, Italy
| | | | | | - Benedetto Falsini
- Institute of Ophthalmology, Università Cattolica del Sacro Cuore, Rome, Italy.,Fondazione Policlinico Universitario "A. Gemelli", IRCCS, Rome, Italy
| | - Adriano Magli
- Department of Pediatric Ophthalmology, University of Salerno, Fisciano (SA), Italy
| | - Matteo Bertelli
- MAGI'S Lab s.r.l., Rovereto, Italy.,MAGI Euregio, Bolzano, Italy
| | - Daniele Dell'Orco
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, Verona, Italy
| |
Collapse
|
17
|
Marino V, Dell'Orco D. Evolutionary-Conserved Allosteric Properties of Three Neuronal Calcium Sensor Proteins. Front Mol Neurosci 2019; 12:50. [PMID: 30899213 PMCID: PMC6417375 DOI: 10.3389/fnmol.2019.00050] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2018] [Accepted: 02/11/2019] [Indexed: 12/21/2022] Open
Abstract
Neuronal Calcium Sensors (NCS) are highly conserved proteins specifically expressed in neurons. Calcium (Ca2+)-binding to their EF-hand motifs results in a conformational change, which is crucial for the recognition of a specific target and the downstream biological process. Here we present a comprehensive analysis of the allosteric communication between Ca2+-binding sites and the target interfaces of three NCS, namely NCS1, recoverin (Rec), and GCAP1. In particular, Rec was investigated in different Ca2+-loading states and in complex with a peptide from the Rhodopsin Kinase (GRK1) while NCS1 was studied in a Ca2+-loaded state in complex with either the same GRK1 target or a peptide from the D2 Dopamine receptor. A Protein Structure Network (PSN) accounting for persistent non-covalent interactions between amino acids was built for each protein state based on exhaustive Molecular Dynamics simulations. Structural network analysis helped unveiling the role of key amino acids in allosteric mechanisms and their evolutionary conservation among homologous proteins. Results for NCS1 highlighted allosteric inter-domain interactions between Ca2+-binding motifs and residues involved in target recognition. Robust long range, allosteric protein-target interactions were found also in Rec, in particular originating from the EF3 motif. Interestingly, Tyr 86, involved the hydrophobic packing of the N-terminal domain, was found to be a key residue for both intra- and inter-molecular communication with EF3, regardless of the presence of target or Ca2+ ions. Finally, based on a comprehensive topological PSN analysis for Rec, NCS1, and GCAP1 and multiple sequence alignments with homolog proteins, we propose that an evolution-driven correlation may exist between the amino acids mediating the highest number of persistent interactions (high-degree hubs) and their conservation. Such conservation is apparently fundamental for the specific structural dynamics required in signaling events.
Collapse
Affiliation(s)
- Valerio Marino
- Section of Biological Chemistry, Department of Neurosciences, Biomedicine, and Movement Sciences, University of Verona, Verona, Italy.,Department of Translational Research and New Technologies in Medicine and Surgery, University of Pisa, Pisa, Italy
| | - Daniele Dell'Orco
- Section of Biological Chemistry, Department of Neurosciences, Biomedicine, and Movement Sciences, University of Verona, Verona, Italy
| |
Collapse
|
18
|
Peshenko IV, Cideciyan AV, Sumaroka A, Olshevskaya EV, Scholten A, Abbas S, Koch KW, Jacobson SG, Dizhoor AM. A G86R mutation in the calcium-sensor protein GCAP1 alters regulation of retinal guanylyl cyclase and causes dominant cone-rod degeneration. J Biol Chem 2019; 294:3476-3488. [PMID: 30622141 DOI: 10.1074/jbc.ra118.006180] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2018] [Revised: 01/04/2019] [Indexed: 11/06/2022] Open
Abstract
The guanylyl cyclase-activating protein, GCAP1, activates photoreceptor membrane guanylyl cyclase (RetGC) in the light, when free Ca2+ concentrations decline, and decelerates the cyclase in the dark, when Ca2+ concentrations rise. Here, we report a novel mutation, G86R, in the GCAP1 (GUCA1A) gene in a family with a dominant retinopathy. The G86R substitution in a "hinge" region connecting EF-hand domains 2 and 3 in GCAP1 strongly interfered with its Ca2+-dependent activator-to-inhibitor conformational transition. The G86R-GCAP1 variant activated RetGC at low Ca2+ concentrations with higher affinity than did the WT GCAP1, but failed to decelerate the cyclase at the Ca2+ concentrations characteristic of dark-adapted photoreceptors. Ca2+-dependent increase in Trp94 fluorescence, indicative of the GCAP1 transition to its RetGC inhibiting state, was suppressed and shifted to a higher Ca2+ range. Conformational changes in G86R GCAP1 detectable by isothermal titration calorimetry (ITC) also became less sensitive to Ca2+, and the dose dependence of the G86R GCAP1-RetGC1 complex inhibition by retinal degeneration 3 (RD3) protein was shifted toward higher than normal concentrations. Our results indicate that the flexibility of the hinge region between EF-hands 2 and 3 is required for placing GCAP1-regulated Ca2+ sensitivity of the cyclase within the physiological range of intracellular Ca2+ at the expense of reducing GCAP1 affinity for the target enzyme. The disease-linked mutation of the hinge Gly86, leading to abnormally high affinity for the target enzyme and reduced Ca2+ sensitivity of GCAP1, is predicted to abnormally elevate cGMP production and Ca2+ influx in photoreceptors in the dark.
Collapse
Affiliation(s)
- Igor V Peshenko
- From the Pennsylvania College of Optometry, Salus University, Elkins Park, Pennsylvania 19027
| | - Artur V Cideciyan
- the Department of Ophthalmology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, and
| | - Alexander Sumaroka
- the Department of Ophthalmology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, and
| | - Elena V Olshevskaya
- From the Pennsylvania College of Optometry, Salus University, Elkins Park, Pennsylvania 19027
| | - Alexander Scholten
- the Department of Neuroscience, University of Oldenburg, Oldenburg D-26129, Germany
| | - Seher Abbas
- the Department of Neuroscience, University of Oldenburg, Oldenburg D-26129, Germany
| | - Karl-Wilhelm Koch
- the Department of Neuroscience, University of Oldenburg, Oldenburg D-26129, Germany
| | - Samuel G Jacobson
- the Department of Ophthalmology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, and
| | - Alexander M Dizhoor
- From the Pennsylvania College of Optometry, Salus University, Elkins Park, Pennsylvania 19027,
| |
Collapse
|
19
|
Vallone R, Dal Cortivo G, D'Onofrio M, Dell'Orco D. Preferential Binding of Mg 2+ Over Ca 2+ to CIB2 Triggers an Allosteric Switch Impaired in Usher Syndrome Type 1J. Front Mol Neurosci 2018; 11:274. [PMID: 30174586 PMCID: PMC6107761 DOI: 10.3389/fnmol.2018.00274] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2018] [Accepted: 07/20/2018] [Indexed: 12/20/2022] Open
Abstract
Calcium and integrin binding protein 2 (CIB2) shares with the other members of the CIB family the ability to bind Ca2+ and Mg2+ via two functional EF-hand motifs, namely EF3 and EF4. As a cation sensor, CIB2 is able to switch to a conformation likely associated with specific biological functions yet to be clarified. Recent findings demonstrate the involvement of CIB2 in hearing physiology and a single, conservative point mutation (p.E64D) has been related to Usher Syndrome type 1J (USH1J) and non-syndromic hearing loss. We present an exhaustive biochemical and biophysical characterization of human wild type (WT) and E64D CIB2. We found that CIB2 does not possibly work as a calcium sensor under physiological conditions, its affinity for Ca2+ (Kdapp = 0.5 mM) being too low for detecting normal intracellular levels. Instead, CIB2 displays a significantly high affinity for Mg2+ (Kdapp = 290 μM), and it is probably Mg2+ -bound under physiological conditions. At odds with the homologous protein CIB1, CIB2 forms a non-covalent dimer under conditions that mimic the physiological ones, and as such it interacts with its physiological target α7B integrin. NMR spectroscopy revealed a long-range allosteric communication between the residue E64, located at the N-terminal domain, and the metal cation binding site EF3, located at the C-terminal domain. The conservative E64D mutation breaks up such inter-domain communication resulting in the impaired ability of CIB2 to switch to its Mg2+-bound form. The ability to bind the target integrin peptide was substantially conserved for E64D CIB2, thus suggesting that the molecular defect associated with USH1J resides in its inability to sense Mg2+ and adopt the required conformation.
Collapse
Affiliation(s)
- Rosario Vallone
- Section of Biological Chemistry, Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Verona, Italy
| | - Giuditta Dal Cortivo
- Section of Biological Chemistry, Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Verona, Italy
| | | | - Daniele Dell'Orco
- Section of Biological Chemistry, Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Verona, Italy
| |
Collapse
|
20
|
Sharon D, Wimberg H, Kinarty Y, Koch KW. Genotype-functional-phenotype correlations in photoreceptor guanylate cyclase (GC-E) encoded by GUCY2D. Prog Retin Eye Res 2018; 63:69-91. [DOI: 10.1016/j.preteyeres.2017.10.003] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2017] [Revised: 10/16/2017] [Accepted: 10/16/2017] [Indexed: 01/09/2023]
|
21
|
Vocke F, Weisschuh N, Marino V, Malfatti S, Jacobson SG, Reiff CM, Dell'Orco D, Koch KW. Dysfunction of cGMP signalling in photoreceptors by a macular dystrophy-related mutation in the calcium sensor GCAP1. Hum Mol Genet 2017; 26:133-144. [PMID: 28025326 DOI: 10.1093/hmg/ddw374] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2016] [Accepted: 10/27/2016] [Indexed: 12/28/2022] Open
Abstract
Macular dystrophy leads to progressive loss of central vision and shows symptoms similar to age-related macular degeneration. Genetic screening of patients diagnosed with macular dystrophy disclosed a novel mutation in the GUCA1A gene, namely a c.526C > T substitution leading to the amino acid substitution p.L176F in the guanylate cyclase-activating protein 1 (GCAP1). The same variant was found in three families showing an autosomal dominant mode of inheritance. For a full functional characterization of the L176F mutant we expressed and purified the mutant protein and measured key parameters of its activating properties, its Ca2+/Mg2+-binding, and its Ca2+-induced conformational changes in comparison to the wildtype protein. The mutant was less sensitive to changes in free Ca2+, resulting in a constitutively active form under physiological Ca2+-concentration, showed significantly higher activation rates than the wildtype (90-fold versus 20-fold) and interacted with an higher apparent affinity with its target guanylate cyclase. However, direct Ca2+-binding of the mutant was nearly similar to the wildtype; binding of Mg2+ occurred with higher affinity. We performed molecular dynamics simulations for comparing the Ca2+-saturated inhibiting state of GCAP1 with the Mg2+-bound activating states. The L176F mutant exhibited significantly lower flexibility, when three Ca2+ or two Mg2+ were bound forming probably the structural basis for the modified GCAP1 function.
Collapse
Affiliation(s)
- Farina Vocke
- Department of Neuroscience, Biochemistry Group, University of Oldenburg, Oldenburg, Germany
| | - Nicole Weisschuh
- Molecular Genetics Laboratory, Institute for Ophthalmic Research, University of Tübingen, Germany
| | - Valerio Marino
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, Verona, Italy and
| | - Silvia Malfatti
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, Verona, Italy and
| | - Samuel G Jacobson
- Scheie Eye Institute, Department of Ophthalmology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Charlotte M Reiff
- Molecular Genetics Laboratory, Institute for Ophthalmic Research, University of Tübingen, Germany
| | - Daniele Dell'Orco
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, Verona, Italy and
| | - Karl-Wilhelm Koch
- Department of Neuroscience, Biochemistry Group, University of Oldenburg, Oldenburg, Germany
| |
Collapse
|
22
|
Marino V, Borsatto A, Vocke F, Koch KW, Dell'Orco D. CaF 2 nanoparticles as surface carriers of GCAP1, a calcium sensor protein involved in retinal dystrophies. NANOSCALE 2017; 9:11773-11784. [PMID: 28785759 DOI: 10.1039/c7nr03288a] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
CaF2-based nanoparticles (NP) are promising biocompatible tools for nanomedicine applications. The structure of the NP crystal lattice allows for specific interactions with Ca2+-binding proteins through their EF-hand cation binding motifs. Here we investigated the interaction of 23 nm citrate-coated CaF2 NP with a calcium sensor protein GCAP1 that is normally expressed in photoreceptor cells and involved in the regulation of the early steps of vision. Protein-NP interactions were thoroughly investigated for the wild type (WT) GCAP1 as well as for a variant carrying the Asp 100 to Glu mutation (D100E), which prevents the binding of Ca2+ to the highest affinity site and is linked to cone dystrophy. Circular dichroism and fluorescence spectroscopy showed that protein structure and Ca2+-sensing capability are conserved for both variants upon interaction with the NP surface, although the interaction mode depends on the specific occupation of Ca2+-binding sites. NP binding stabilizes the structure of the bound GCAP1 and occurs with nanomolar affinity, as probed by isothermal titration calorimetry. Surface plasmon resonance revealed a fully reversible binding compatible with physiologically relevant kinetics of protein release whereas biochemical assays indicated a residual capability for NP-dissociated GCAP1 to regulate the target retinal guanylate cyclase. Our study constitutes a proof of concept that CaF2 NP could be optimized to serve as biologically compatible carriers of high amounts of functional GCAP1 in photoreceptors affected by retinal dystrophies.
Collapse
Affiliation(s)
- Valerio Marino
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, Verona, Italy.
| | - Alberto Borsatto
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, Verona, Italy.
| | - Farina Vocke
- Department of Neuroscience, Biochemistry Group, University of Oldenburg, Oldenburg, Germany
| | - Karl-Wilhelm Koch
- Department of Neuroscience, Biochemistry Group, University of Oldenburg, Oldenburg, Germany
| | - Daniele Dell'Orco
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, Verona, Italy.
| |
Collapse
|
23
|
Salamanca Viloria J, Allega MF, Lambrughi M, Papaleo E. An optimal distance cutoff for contact-based Protein Structure Networks using side-chain centers of mass. Sci Rep 2017; 7:2838. [PMID: 28588190 PMCID: PMC5460117 DOI: 10.1038/s41598-017-01498-6] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Accepted: 03/28/2017] [Indexed: 02/05/2023] Open
Abstract
Proteins are highly dynamic entities attaining a myriad of different conformations. Protein side chains change their states during dynamics, causing clashes that are propagated at distal sites. A convenient formalism to analyze protein dynamics is based on network theory using Protein Structure Networks (PSNs). Despite their broad applicability, few efforts have been devoted to benchmarking PSN methods and to provide the community with best practices. In many applications, it is convenient to use the centers of mass of the side chains as nodes. It becomes thus critical to evaluate the minimal distance cutoff between the centers of mass which will provide stable network properties. Moreover, when the PSN is derived from a structural ensemble collected by molecular dynamics (MD), the impact of the MD force field has to be evaluated. We selected a dataset of proteins with different fold and size and assessed the two fundamental properties of the PSN, i.e. hubs and connected components. We identified an optimal cutoff of 5 Å that is robust to changes in the force field and the proteins. Our study builds solid foundations for the harmonization and standardization of the PSN approach.
Collapse
Affiliation(s)
- Juan Salamanca Viloria
- Computational Biology Laboratory, Danish Cancer Society Research Center, Strandboulevarden 49, 2100, Copenhagen, Denmark
| | - Maria Francesca Allega
- Computational Biology Laboratory, Danish Cancer Society Research Center, Strandboulevarden 49, 2100, Copenhagen, Denmark
| | - Matteo Lambrughi
- Computational Biology Laboratory, Danish Cancer Society Research Center, Strandboulevarden 49, 2100, Copenhagen, Denmark
| | - Elena Papaleo
- Computational Biology Laboratory, Danish Cancer Society Research Center, Strandboulevarden 49, 2100, Copenhagen, Denmark.
| |
Collapse
|
24
|
GUCA1A mutation causes maculopathy in a five-generation family with a wide spectrum of severity. Genet Med 2017; 19:945-954. [PMID: 28125083 PMCID: PMC5548935 DOI: 10.1038/gim.2016.217] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Accepted: 11/18/2016] [Indexed: 12/19/2022] Open
Abstract
PURPOSE The aim of this study was to investigate the genetic basis and pathogenic mechanism of variable maculopathies, ranging from mild photoreceptor degeneration to central areolar choroidal dystrophy, in a five-generation family. METHODS Clinical characterizations, whole-exome sequencing, and genome-wide linkage analysis were carried out on the family. Zebrafish models were used to investigate the pathogenesis of GUCA1A mutations. RESULTS A novel mutation, GUCA1A p.R120L, was identified in the family and predicted to alter the tertiary structure of guanylyl cyclase-activating protein 1, a photoreceptor-expressed protein encoded by the GUCA1A gene. The mutation was shown in zebrafish to cause significant disruptions in photoreceptors and retinal pigment epithelium, together with atrophies of retinal vessels and choriocapillaris. Those phenotypes could not be fully rescued by exogenous wild-type GUCA1A, suggesting a likely gain-of-function mechanism for p.R120L. GUCA1A p.D100E, another mutation previously implicated in cone dystrophy, also impaired the retinal pigment epithelium and photoreceptors in zebrafish, but probably via a dominant negative effect. CONCLUSION We conclude that GUCA1A mutations could cause significant variability in maculopathies, including central areolar choroidal dystrophy, which represents a severe pattern of maculopathy. The diverse pathogenic modes of GUCA1A mutations may explain the phenotypic diversities.Genet Med advance online publication 26 January 2017.
Collapse
|
25
|
Marino V, Dell'Orco D. Allosteric communication pathways routed by Ca 2+/Mg 2+ exchange in GCAP1 selectively switch target regulation modes. Sci Rep 2016; 6:34277. [PMID: 27739433 PMCID: PMC5064319 DOI: 10.1038/srep34277] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Accepted: 09/09/2016] [Indexed: 12/11/2022] Open
Abstract
GCAP1 is a neuronal calcium sensor protein that regulates the phototransduction cascade in vertebrates by switching between activator and inhibitor of the target guanylate cyclase (GC) in a Ca2+-dependent manner. We carried out exhaustive molecular dynamics simulations of GCAP1 and determined the intramolecular communication pathways involved in the specific GC activator/inhibitor switch. The switch was found to depend on the Mg2+/Ca2+ loading states of the three EF hands and on the way the information is transferred from each EF hand to specific residues at the GCAP1/GC interface. Post-translational myristoylation is fundamental to mediate long range allosteric interactions including the EF2-EF4 coupling and the communication between EF4 and the GC binding interface. Some hubs in the identified protein network are the target of retinal dystrophy mutations, suggesting that the lack of complete inhibition of GC observed in many cases is likely due to the perturbation of intra/intermolecular communication routes.
Collapse
Affiliation(s)
- Valerio Marino
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, strada le Grazie 8, I-37134 Verona, Italy
| | - Daniele Dell'Orco
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, strada le Grazie 8, I-37134 Verona, Italy.,Centre for BioMedical Computing (CBMC), University of Verona, strada le Grazie 8, I-37134 Verona, Italy
| |
Collapse
|