# Exocytosis fuels plasma membrane expansion in developing neurons

> **NIH NIH R01** · UNIV OF NORTH CAROLINA CHAPEL HILL · 2021 · $384,007

## Abstract

Project Summary
During development, neurons acquire a polarized, elongated, and complex morphology, which
requires a significant expansion of plasma membrane surface area. Surface increases have
been estimated to reach upward of 20% per day, which far exceeds concomitant neuronal
volume increases. We previously demonstrated that SNARE-mediated exocytosis is required
during neuritogenesis and axon branching, presumably to provide membrane material to the
expanding plasma membrane, which can only stretch ~2-3% prior to rupture. Asymmetric
exocytosis has also been implicated in the attractive axonal turning responses that are critical
for axon guidance. Achieving proper neuronal morphogenesis and connectivity is central to the
formation of a functional nervous system. Together these factors underscore the significance of
regulated exocytosis in developing neurons, even prior to synaptogenesis. Over the last 40
years, a multitude of components involved in exocytosis have been identified, although this list
is not exhaustive. Further, mechanisms that regulate the mode, progression, frequency, or
spatiotemporal organization of vesicle fusion with the membrane, all of which are poised to
modulate neuronal morphogenesis, have not been defined. To visualize exocytic events in
developing neurons, we express a pH-sensitive variant of GFP (pHluorin) attached to the
lumenal side of a v-SNARE, such as VAMP2 or VAMP7, to illuminate the occurrence of fusion
pore opening between the acidic vesicular lumen and the neutral extracellular space. Analysis
of such images has remained a time-intensive, non-automated bottleneck, delaying
understanding of this fundamental cellular behavior. We developed a fully-automated computer-
vision software for the detection and analysis of VAMP-pHluorin mediated exocytic events that
will quantitatively reveal the spatial and temporal organization and regulation of exocytosis in
developing neurons at a level of detail previously unattainable. We exploit this innovative
methodology along with unbiased proteomics, microfluidics, biochemical and cell biological
approaches to investigate the relationship between exocytosis and neuronal morphogenesis
and identifying the molecular mechanisms that regulate exocytosis in developing neurons.

## Key facts

- **NIH application ID:** 10159320
- **Project number:** 5R01NS112326-03
- **Recipient organization:** UNIV OF NORTH CAROLINA CHAPEL HILL
- **Principal Investigator:** Stephanie Gupton
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $384,007
- **Award type:** 5
- **Project period:** 2019-08-01 → 2024-04-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10159320

## Citation

> US National Institutes of Health, RePORTER application 10159320, Exocytosis fuels plasma membrane expansion in developing neurons (5R01NS112326-03). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10159320. Licensed CC0.

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