Autism-associated mutations in the CaVβ2 calcium-channel subunit increase Ba2+-currents and lead to differential modulation by the RGK-protein Gem

Despang, Patrick; Salamon, Sarah; Breitenkamp, Alexandra F.; Kuzmenkina, Elza; Herzig, Stefan; Matthes, Jan

doi:10.1016/j.nbd.2019.104721

Cited by 11 publications

(12 citation statements)

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“…Additional to their role in promoting α 1 membrane incorporation, the β subunits modulate in an isoform and splice variant-specific manner the channel's voltage dependence [80,122,124,126] and time course [122,130] of activation and inactivation. The β subunits alter the whole cell HVCC Ca 2+ current kinetics by modulating the single-channel open probability properties [133][134][135][136][137].…”

Section: β-Subunitsmentioning

confidence: 99%

Role of High Voltage-Gated Ca2+ Channel Subunits in Pancreatic β-Cell Insulin Release. From Structure to Function

Tuluc

Theiner

Jacobo-Piqueras

et al. 2021

Cells

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The pancreatic islets of Langerhans secrete several hormones critical for glucose homeostasis. The β-cells, the major cellular component of the pancreatic islets, secrete insulin, the only hormone capable of lowering the plasma glucose concentration. The counter-regulatory hormone glucagon is secreted by the α-cells while δ-cells secrete somatostatin that via paracrine mechanisms regulates the α- and β-cell activity. These three peptide hormones are packed into secretory granules that are released through exocytosis following a local increase in intracellular Ca2+ concentration. The high voltage-gated Ca2+ channels (HVCCs) occupy a central role in pancreatic hormone release both as a source of Ca2+ required for excitation-secretion coupling as well as a scaffold for the release machinery. HVCCs are multi-protein complexes composed of the main pore-forming transmembrane α1 and the auxiliary intracellular β, extracellular α2δ, and transmembrane γ subunits. Here, we review the current understanding regarding the role of all HVCC subunits expressed in pancreatic β-cell on electrical activity, excitation-secretion coupling, and β-cell mass. The evidence we review was obtained from many seminal studies employing pharmacological approaches as well as genetically modified mouse models. The significance for diabetes in humans is discussed in the context of genetic variations in the genes encoding for the HVCC subunits.

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Section: β-Subunitsmentioning

confidence: 99%

Role of High Voltage-Gated Ca2+ Channel Subunits in Pancreatic β-Cell Insulin Release. From Structure to Function

Tuluc

Theiner

Jacobo-Piqueras

et al. 2021

Cells

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“…The Gem and Ca V β co-immunoprecipitation experiments were performed as described previously (Despang et al 2020). In brief, tsA cells were harvested 48-72 h after transfection in ice cold PBS and lysed in lysis buffer (50-mM Tris; 100-mM NaCl; 10-mM EDTA; 0.4% TritonX-100; 0.4% NP-40; pH: 7.5 with HCl).…”

Section: Co-immunoprecipitation and Western Blotmentioning

confidence: 99%

“…Whole-cell recordings were performed as in our previous studies (Breitenkamp et al 2014;Despang et al 2020;Graziano et al 2021). Recordings of EGFP-positive cells were obtained 48-72 h after transfection.…”

Section: Electrophysiological Recordingsmentioning

confidence: 99%

“…In whole-cell recordings, two of the resulting Ca V β 2 mutants (p.G167S, p.S197F) led to a slowed and the third (p.F240L) to an accelerated current inactivation. In a detailed subsequent study, we could show that these mutations and an N-terminal mutation at position 2 (p.V2D) led to a significantly higher single-channel activity compared to channels containing a wildtype (WT) Ca V β 2 (Despang et al 2020). Mutated and WT Ca V β 2 subunits interacted with the inhibitory RGK-protein Gem but differed in the extent and characteristics of being modulated by Gem.…”

Section: Introductionmentioning

confidence: 95%

“…(2) A mutant Ca V 1.2 protein characterized by impaired current inactivation has been shown to underly the Timothy syndrome, a monogenetic "model disease" for ASD (Splawski et al 2004;Breitenkamp et al 2015). (3) In our previous studies, we identified functional effects of Ca V β 2 variants when co-expressed with Ca V 1.2 (Breitenkamp et al 2014;Despang et al 2020;Graziano et al 2021). For the following reasons, Ca V 2.2 was chosen as a second VGCC pore subunit for our analysis of the Ca V β 1b_R296C variant: Ca V 2.2 is expressed predominantly in neurons where most of the central nervous system's synapses rely on Ca V 2.2 and Ca V 2.1 for fast synaptic transmission (Wheeler et al 1994;Catterall et al 2021).…”

Section: Introductionmentioning

confidence: 99%

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Inhibitory effects on L- and N-type calcium channels by a novel CaVβ1 variant identified in a patient with autism spectrum disorder

Despang

Salamon

Breitenkamp

et al. 2022

Naunyn-Schmiedeberg's Arch Pharmacol

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Voltage-gated calcium channel (VGCC) subunits have been genetically associated with autism spectrum disorders (ASD). The properties of the pore-forming VGCC subunit are modulated by auxiliary β-subunits, which exist in four isoforms (CaVβ1-4). Our previous findings suggested that activation of L-type VGCCs is a common feature of CaVβ2 subunit mutations found in ASD patients. In the current study, we functionally characterized a novel CaVβ1b variant (p.R296C) identified in an ASD patient. We used whole-cell and single-channel patch clamp to study the effect of CaVβ1b_R296C on the function of L- and N-type VGCCs. Furthermore, we used co-immunoprecipitation followed by Western blot to evaluate the interaction of the CaVβ1b-subunits with the RGK-protein Gem. Our data obtained at both, whole-cell and single-channel levels, show that compared to a wild-type CaVβ1b, the CaVβ1b_R296C variant inhibits L- and N-type VGCCs. Interaction with and modulation by the RGK-protein Gem seems to be intact. Our findings indicate functional effects of the CaVβ1b_R296C variant differing from that attributed to CaVβ2 variants found in ASD patients. Further studies have to detail the effects on different VGCC subtypes and on VGCC expression.

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A New Homozygous CACNB2 Mutation has Functional Relevance and Supports a Role for Calcium Channels in Autism Spectrum Disorder

Graziano

Despang

Palombo

et al. 2020

J Autism Dev Disord

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BackgroundDiagnostic yield in patients with autism spectrum disorder (ASD) has improved over the last years, thanks to the introduction of whole genome arrays and next generation sequencing, but etiology is still unknown for the majority of cases. Among distinct cellular pathways, evidence implicating dysregulation of cellular calcium homeostasis in ASD pathogenesis has been accumulating, and speci c mutations in voltagegated calcium channels found in patients with autism were shown to be functionally relevant. MethodsWhole exome sequencing and Sanger sequencing were performed to identify and con rm variants in a girl with ASD, global developmental delay and precocious puberty, born of rst-degree cousins. Sitedirected mutagenesis was used to generate a human Ca V β 2d calcium channel subunit carrying a CACNB2 mutation. Whole-cell patch-clamp recordings were performed to reveal functional effects of mutant Ca V β 2d on Ba 2+ -currents mediated by L-type (Ca V 1.2) calcium channels in transiently transfected HEK-293 cells. ResultsIn an ASD patient, we identi ed a rare homozygous variant (p.Arg70Cys) in the CACNB2 gene coding for the auxiliary Ca V β 2 subunit of voltage-gated calcium channels. In a recombinant system, the Ca V β 2 variant, which was not previously associated to ASD, was found to alter Ca V 1.2 calcium channel function by signi cantly affecting activation and inactivation of whole-cell Ba 2+ -currents. LimitationsAlthough the evidence of CACNB2 involvement in ASD is slowly accumulating, the number of reported patients is very limited. Deep clinical phenotyping and functional studies in larger sets of subjects will be instrumental to fully understand the penetrance and outcome of CACNB2 variants. ConclusionsThe p.Arg70Cys variant in CACNB2 shows functional consequences similar to other ASD-associated Ca V β 2 mutations. These results support the idea of CACNB2 variations contributing to the development of ASD and hint to a rare form of Mendelian recessive autism with possible speci c comorbidities.

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Autism-associated mutations in the CaVβ2 calcium-channel subunit increase Ba2+-currents and lead to differential modulation by the RGK-protein Gem

Cited by 11 publications

References 67 publications

Role of High Voltage-Gated Ca2+ Channel Subunits in Pancreatic β-Cell Insulin Release. From Structure to Function

Role of High Voltage-Gated Ca2+ Channel Subunits in Pancreatic β-Cell Insulin Release. From Structure to Function

Inhibitory effects on L- and N-type calcium channels by a novel CaVβ1 variant identified in a patient with autism spectrum disorder

A New Homozygous CACNB2 Mutation has Functional Relevance and Supports a Role for Calcium Channels in Autism Spectrum Disorder

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