Specific presynaptic functions require distinct Drosophila Ca_v2 splice isoforms.

Area of Science:

• Neuroscience
• Molecular Biology
• Genetics

Background:

• Vertebrate synapses utilize diverse Ca_v2 channel subtypes to regulate presynaptic function.
• Invertebrates typically possess a single Ca_v2 gene, suggesting alternative mechanisms for functional diversification.
• The Drosophila Ca_v2 homolog, cacophony (cac), is crucial for synaptic vesicle release at active zones (AZs).

Purpose of the Study:

• To investigate how alternative splicing of the Drosophila cac gene enhances functional diversity.
• To determine the roles of two specific mutually exclusive exon pairs in cac channel function.
• To elucidate the impact of alternative splicing on presynaptic calcium channel localization and synaptic transmission.

Main Methods:

• Analysis of alternative splicing events in the Drosophila cac gene.
• Electrophysiological recordings at the Drosophila larval neuromuscular junction.
• Immunolocalization studies to determine channel localization at presynaptic active zones.

Main Results:

• Alternative splicing in the voltage sensor domain alters channel activation voltage; only the higher-activation voltage isoform localizes to AZs and is essential for normal synapse function.
• Alternative splicing in the Ca_β/G_βγ binding loop affects AZ channel number, release probability, and presynaptic homeostatic plasticity.
• Reduced channel number due to splicing impacts short-term plasticity, which can be rescued by adjusting external calcium concentrations.

Conclusions:

• Alternative splicing of the single Drosophila cac gene provides a versatile mechanism to regulate distinct aspects of presynaptic function.
• Splicing-dependent localization and expression levels of cac channels are critical for synaptic transmission and plasticity.
• This study highlights alternative splicing as a key strategy for diversifying ion channel function in invertebrates.