Proteolytic maturation of α₂δ controls the probability of synaptic vesicular release

Thank you for submitting your article "Proteolytic Maturation of α₂δ Controls the Probability of Synaptic Vesicular Release" for consideration by eLife. Your article has been reviewed by two peer reviewers, including Mary B Kennedy as the Reviewing Editor and Reviewer #1, and the evaluation has been overseen by Richard Aldrich as the Senior Editor.

The reviewers have discussed the reviews with one another and the Reviewing Editor has drafted this decision to help you prepare a revised submission.

Summary:

The study by Ferron et al. builds on an earlier publication in eLife from the Dolphin group showing that proteolytic processing of α₂δ, an auxiliary subunit of N-type calcium channels (Ca_v2.2) is necessary for its function in trafficking of the channel to the presynaptic terminal. Here they extend that study by showing that proteolytic processing increases the probability of release at presynaptic terminals, and modulates asynchronous release that follows a burst of action potentials. They state that this effect likely results from its effects on the function of presynaptic Ca_v channels. Preventing proteolytic processing by mutating the cleavage site results in a reduction of synaptic vesicle exocytosis as determined with pHluorin-tagged VGlut and reconstituting this processing by co-expressing a protease that cleaves the mutated cleavage site rescues the exocytosis. They also add the biochemical observation that proteolytic processing increases the strength of association of α₂δ with the channel.

Minor revisions:

The study is appropriate as a research advance. The reviewers had some requested revisions that should be able to be accomplished quickly.

1) One reviewer noted that the use of optical methods to measure the RRP and asynchronous release is a relatively new technique. If the authors have used an additional more standard measure such as hyperosmotically induced exocytosis (high glucose), it would strengthen the paper to include it. Otherwise, the authors could briefly review the evidence supporting the validity of their assay in the Discussion.

2) References: The reference to Page et al., submitted, should be changed to "in press", or unpublished results, as appropriate. The Ariel and Ryan (2010) is important to validate the interpretation of the optical measurements of RRP and asynchronous release. The reference to Ariel and Ryan (2010) is incomplete and should include the article and doi: 4:18. doi: 10.3389/fncir.2010.00018.

3) Recent evidence indicates that α₂δ also interacts with NMDARs. It would be good to discuss these findings in the Discussion in addition to the α₂δ association with BK channels.