Autism-Linked Mutations in α<sub>2</sub>δ-1 and α<sub>2</sub>δ-3 Reduce Protein Membrane Expression but Affect Neither Calcium Channels nor Trans-Synaptic Signaling
Background: α<sub>2</sub>δ proteins regulate membrane trafficking and biophysical properties of voltage-gated calcium channels. Moreover, they modulate axonal wiring, synapse formation, and trans-synaptic signaling. Several rare missense variants in CACNA2D1 (coding for α<sub>2<...
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| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2024-11-01
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| Series: | Pharmaceuticals |
| Subjects: | |
| Online Access: | https://www.mdpi.com/1424-8247/17/12/1608 |
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| Summary: | Background: α<sub>2</sub>δ proteins regulate membrane trafficking and biophysical properties of voltage-gated calcium channels. Moreover, they modulate axonal wiring, synapse formation, and trans-synaptic signaling. Several rare missense variants in CACNA2D1 (coding for α<sub>2</sub>δ-1) and CACNA2D3 (coding for α<sub>2</sub>δ-3) genes were identified in patients with autism spectrum disorder (ASD). However, the pathogenicity of these variants is not known, and the molecular mechanism by which α<sub>2</sub>δ proteins may contribute to the pathophysiology of autism is, as of today, not understood. Therefore, in this study we functionally characterized two heterozygous missense variants in α<sub>2</sub>δ-1 (p.R351T) and α<sub>2</sub>δ-3 (p.A275T), previously identified in patients with ASD. Methods: Electrophysiological recordings in transfected tsA201 cells were used to study specific channel-dependent functions of mutated α<sub>2</sub>δ proteins. Membrane expression, presynaptic targeting, and trans-synaptic signaling of mutated α<sub>2</sub>δ proteins were studied upon expression in murine cultured hippocampal neurons. Results: Homologous expression of both mutated α<sub>2</sub>δ proteins revealed a strongly reduced membrane expression and synaptic localization compared to the corresponding wild type α<sub>2</sub>δ proteins. Moreover, the A275T mutation in α<sub>2</sub>δ-3 resulted in an altered glycosylation pattern upon heterologous expression. However, neither of the mutations compromised the biophysical properties of postsynaptic L-type (Ca<sub>V</sub>1.2 and Ca<sub>V</sub>1.3) and presynaptic P/Q-type (Ca<sub>V</sub>2.1) channels when co-expressed in tsA201 cells. Furthermore, presynaptic expression of p.R351T in the α<sub>2</sub>δ-1 splice variant lacking exon 23 did not affect trans-synaptic signaling to postsynaptic GABA<sub>A</sub> receptors. Conclusions: Our data provide evidence that the pathophysiological mechanisms of ASD-causing mutations of α<sub>2</sub>δ proteins may not involve their classical channel-dependent and trans-synaptic functions. Alternatively, these mutations may induce subtle changes in synapse formation or neuronal network function, highlighting the need for future α<sub>2</sub>δ protein-linked disease models. |
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| ISSN: | 1424-8247 |