A Novel <i>GUCA1A</i> Variant Associated with Cone Dystrophy Alters cGMP Signaling in Photoreceptors by Strongly Interacting with and Hyperactivating Retinal Guanylate Cyclase
Guanylate cyclase-activating protein 1 (GCAP1), encoded by the <i>GUCA1A</i> 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...
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MDPI AG
2021-10-01
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| Series: | International Journal of Molecular Sciences |
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| Online Access: | https://www.mdpi.com/1422-0067/22/19/10809 |
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| author | Amedeo Biasi Valerio Marino Giuditta Dal Cortivo Paolo Enrico Maltese Antonio Mattia Modarelli Matteo Bertelli Leonardo Colombo Daniele Dell’Orco |
| author_facet | Amedeo Biasi Valerio Marino Giuditta Dal Cortivo Paolo Enrico Maltese Antonio Mattia Modarelli Matteo Bertelli Leonardo Colombo Daniele Dell’Orco |
| author_sort | Amedeo Biasi |
| collection | DOAJ |
| description | Guanylate cyclase-activating protein 1 (GCAP1), encoded by the <i>GUCA1A</i> 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 Ca<sup>2+</sup>, thereby ensuring a timely regulation of the phototransduction cascade. We found a novel variant of <i>GUCA1A</i> 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 Ca<sup>2+</sup> 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 Mg<sup>2+</sup> alone and Mg<sup>2+</sup> and Ca<sup>2+</sup>. Enzymatic assays showed that N104H-GCAP1 strongly interacts with the GC, with an affinity that doubles that of the WT. The doubled IC<sub>50</sub> 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 Ca<sup>2+</sup>. The structural region at the interface with the GC may acquire enhanced flexibility under high Ca<sup>2+</sup> 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 Ca<sup>2+</sup> levels, which would ultimately lead to toxic accumulation of cGMP and Ca<sup>2+</sup> in the photoreceptor outer segment, thus triggering cell death. |
| first_indexed | 2024-03-10T06:59:22Z |
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| institution | Directory Open Access Journal |
| issn | 1661-6596 1422-0067 |
| language | English |
| last_indexed | 2024-03-10T06:59:22Z |
| publishDate | 2021-10-01 |
| publisher | MDPI AG |
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| spelling | doaj.art-e368019cccc64f0a8932db8049e6ea502023-11-22T16:15:51ZengMDPI AGInternational Journal of Molecular Sciences1661-65961422-00672021-10-0122191080910.3390/ijms221910809A Novel <i>GUCA1A</i> Variant Associated with Cone Dystrophy Alters cGMP Signaling in Photoreceptors by Strongly Interacting with and Hyperactivating Retinal Guanylate CyclaseAmedeo Biasi0Valerio Marino1Giuditta Dal Cortivo2Paolo Enrico Maltese3Antonio Mattia Modarelli4Matteo Bertelli5Leonardo Colombo6Daniele Dell’Orco7Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, 37134 Verona, ItalyDepartment of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, 37134 Verona, ItalyDepartment of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, 37134 Verona, ItalyMAGI’S Lab s.r.l., 38068 Rovereto, ItalyDepartment of Ophthalmology, ASST Santi Paolo e Carlo Hospital, University of Milan, 20142 Milano, ItalyMAGI’S Lab s.r.l., 38068 Rovereto, ItalyDepartment of Ophthalmology, ASST Santi Paolo e Carlo Hospital, University of Milan, 20142 Milano, ItalyDepartment of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, 37134 Verona, ItalyGuanylate cyclase-activating protein 1 (GCAP1), encoded by the <i>GUCA1A</i> 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 Ca<sup>2+</sup>, thereby ensuring a timely regulation of the phototransduction cascade. We found a novel variant of <i>GUCA1A</i> 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 Ca<sup>2+</sup> 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 Mg<sup>2+</sup> alone and Mg<sup>2+</sup> and Ca<sup>2+</sup>. Enzymatic assays showed that N104H-GCAP1 strongly interacts with the GC, with an affinity that doubles that of the WT. The doubled IC<sub>50</sub> 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 Ca<sup>2+</sup>. The structural region at the interface with the GC may acquire enhanced flexibility under high Ca<sup>2+</sup> 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 Ca<sup>2+</sup> levels, which would ultimately lead to toxic accumulation of cGMP and Ca<sup>2+</sup> in the photoreceptor outer segment, thus triggering cell death.https://www.mdpi.com/1422-0067/22/19/10809GUCA1Aphototransductioncone dystrophyguanylyl cyclasephotoreceptorsneuronal calcium sensor |
| spellingShingle | Amedeo Biasi Valerio Marino Giuditta Dal Cortivo Paolo Enrico Maltese Antonio Mattia Modarelli Matteo Bertelli Leonardo Colombo Daniele Dell’Orco A Novel <i>GUCA1A</i> Variant Associated with Cone Dystrophy Alters cGMP Signaling in Photoreceptors by Strongly Interacting with and Hyperactivating Retinal Guanylate Cyclase International Journal of Molecular Sciences GUCA1A phototransduction cone dystrophy guanylyl cyclase photoreceptors neuronal calcium sensor |
| title | A Novel <i>GUCA1A</i> Variant Associated with Cone Dystrophy Alters cGMP Signaling in Photoreceptors by Strongly Interacting with and Hyperactivating Retinal Guanylate Cyclase |
| title_full | A Novel <i>GUCA1A</i> Variant Associated with Cone Dystrophy Alters cGMP Signaling in Photoreceptors by Strongly Interacting with and Hyperactivating Retinal Guanylate Cyclase |
| title_fullStr | A Novel <i>GUCA1A</i> Variant Associated with Cone Dystrophy Alters cGMP Signaling in Photoreceptors by Strongly Interacting with and Hyperactivating Retinal Guanylate Cyclase |
| title_full_unstemmed | A Novel <i>GUCA1A</i> Variant Associated with Cone Dystrophy Alters cGMP Signaling in Photoreceptors by Strongly Interacting with and Hyperactivating Retinal Guanylate Cyclase |
| title_short | A Novel <i>GUCA1A</i> Variant Associated with Cone Dystrophy Alters cGMP Signaling in Photoreceptors by Strongly Interacting with and Hyperactivating Retinal Guanylate Cyclase |
| title_sort | novel i guca1a i variant associated with cone dystrophy alters cgmp signaling in photoreceptors by strongly interacting with and hyperactivating retinal guanylate cyclase |
| topic | GUCA1A phototransduction cone dystrophy guanylyl cyclase photoreceptors neuronal calcium sensor |
| url | https://www.mdpi.com/1422-0067/22/19/10809 |
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