# Single Channel Studies of the Fusion Pore

> **NIH NIH R01** · UNIVERSITY OF WISCONSIN-MADISON · 2022 · $382,090

## Abstract

Project Summary/Abstract
Neurons and endocrine cells release signaling molecules by Ca2+‐triggered exocytosis. Ca2+ enters a nerve terminal or
endocrine cell, binds to a Ca2+ sensor protein, and triggers the fusion of the vesicle membrane with the plasma
membrane to expel some or all of the vesicle content into the extracellular space. To explore the mechanisms of
exocytosis our research focuses on the fusion pore, the initial aqueous passage between the vesicle interior and the
outside of a cell. All secreted molecules pass through a fusion pore, which is strategically situated to exert finely tuned
control over secretion. By measuring amperometry, capacitance, and miniature postsynaptic currents, we probe fusion
pores at the single‐pore level to track structural transitions and monitor responses to biological signals. Studies of the
fusion pore have given us valuable insights into the roles of specific proteins in the control of membrane fusion. In the
previous funding cycle we showed that the vesicle SNARE protein synaptobrevin alters transmitter flux through
synaptic fusion pores in hippocampal neurons. In a remarkable parallel with our earlier work on endocrine fusion, the
implicated synaptic fusion pore residues align precisely with those of endocrine fusion pores. We showed that another
major vesicle protein, synaptophysin, influences exocytosis at multiple stages as fusion pores open and expand. Aim 1
will complete an ongoing effort to explore the role of the transmembrane domains of synaptophysin in the initial
fusion pore. Turning from initial fusion pores to late‐stage fusion pore, we recently developed a new method for
analyzing fusion pore dynamics during spikes in amperometric recordings from endocrine cells. This method tracks
fusion pore permeability as vesicles lose catecholamine. This led to the novel findings that the pore sequentially
expands, contracts, and settles into a metastable state. Aim 2 will use this method to investigate late‐stage fusion
pores to address long‐standing questions about the biological control of vesicle content expulsion. We will probe late‐
stage fusion pores for control by lipid bilayer elasticity, Ca2+, hormone content, GPCR signaling, synaptotagmin, and
synaptophysin/dynamin. Along a related front, we have developed better ways to study synaptic fusion pores. Co‐
cultures between neurons and HEK 293 cells provide a system for studying synaptic transmission with greatly
enhanced resolution. Aim 3 will use this new co‐culture system to study synaptic release and determine how synaptic
fusion pores are controlled by bilayer elasticity, Ca2+, synaptotagmin, and synaptophysin. This work will explore the
largely unknown behavior of synaptic fusion pores and their dynamic control of synaptic release. These three aims will
extend our understanding of initial fusion pores, and open up an exciting new line of investigation into how late‐stage
fusion pores expand and contract in response to biological signal...

## Key facts

- **NIH application ID:** 10366443
- **Project number:** 2R01NS044057-19
- **Recipient organization:** UNIVERSITY OF WISCONSIN-MADISON
- **Principal Investigator:** MEYER B. JACKSON
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $382,090
- **Award type:** 2
- **Project period:** 2002-07-01 → 2022-11-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10366443

## Citation

> US National Institutes of Health, RePORTER application 10366443, Single Channel Studies of the Fusion Pore (2R01NS044057-19). Retrieved via AI Analytics 2026-06-14 from https://api.ai-analytics.org/grant/nih/10366443. Licensed CC0.

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