# Nanoscale dynamics of voltage-gated calcium channels at presynaptic active zones in live C. elegans

> **NIH NIH R21** · UNIVERSITY OF SOUTHERN CALIFORNIA · 2020 · $76,670

## Abstract

ABSTRACT
In neural circuits, adaptive responses to changes in transmitted signals are conveyed by subtle modulations in the strength
of synaptic connections. This short-term synaptic plasticity involves adjustments of the neurotransmitter release probability
of synaptic vesicles (SVs) positioned in presynaptic areas called active zones (AZ). A key function of the AZ molecular
machinery is to precisely position diffusing membrane voltage-gated calcium channels (VGCCs) in registry with primed
SVs, so as to establish the local Ca2+ concentration gradients that ultimately initiate SV fusion and neurotransmitter release.
Previous studies have shown that active zone cytomatrix (CAZ) proteins are determinants of the spatial coupling between
VGCCs and SVs and that the mobility of VGCCs can tune the SV release probability by setting local channel densities and
Ca2+ concentrations. While this suggests that modulation of VGCC dynamics by CAZ proteins could underlie presynaptic
plasticity, a fundamental, yet still unanswered question in synaptic biology is how CAZ proteins regulate the mobility of
VGCCs and precisely positioned them within AZ a few hundreds of nanometer in size, in the first place.
An important challenge in addressing this question has been the absence of methods that allow direct visualization and
quantification of VGCC dynamics at the nanometer scale within AZ of intact synapses in live animals. Using CRISPR
genetics and complementation activated light microscopy (CALM), an in vivo single molecule (SM) imaging technique that
we introduced recently, we have started to define how the molecular machinery of AZ modulates the nanoscale mobility of
VGCCs using the nematode Caenorhabditis elegans (C.elegans) as a live animal model. Our preliminary data demonstrate
that neuronal VGCCs have heterogeneous diffusive behaviors in vivo, and that their nanoscale mobility is effectively
controlled by key CAZ proteins.
Here, we built on this preliminary work to further dissect the molecular mechanisms by which different CAZ proteins
specifically regulate the presynaptic membrane dynamics of VGCCs in order to guaranty precise neurotransmission.
Specifically, we will determine how VGCC dynamics are regulated by (i) the CAZ protein RIM/UNC-10, (ii) coupling to
SVs and (iii) coupling to other CAZ regulators (Aim 1), how the priming levels of SVs at AZ influence the mobility of
VGCCs (Aim 2), and how the presynaptic dense projection centered in the AZ modulates the nanoconfinement zones of
diffusing VGCCs. (Aim 3).
Together, the proposed studies will advance our fundamental understanding of the molecular organization and function of
the synaptic AZ within intact neurons in live animals. It will also provide new models for regulation of neurotransmission
and short-term synaptic plasticity that integrate the nanoscale dynamics of VGCCs and the structural organization of AZ.

## Key facts

- **NIH application ID:** 10254604
- **Project number:** 3R21NS114911-01A1S1
- **Recipient organization:** UNIVERSITY OF SOUTHERN CALIFORNIA
- **Principal Investigator:** Fabien Pinaud
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $76,670
- **Award type:** 3
- **Project period:** 2020-06-01 → 2022-11-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10254604

## Citation

> US National Institutes of Health, RePORTER application 10254604, Nanoscale dynamics of voltage-gated calcium channels at presynaptic active zones in live C. elegans (3R21NS114911-01A1S1). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10254604. Licensed CC0.

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