# Control of calcium flux and mitochondrial fission by the Charcot Marie Tooth disease protein Mfn2.

> **NIH NIH R01** · UNIVERSITY OF CALIFORNIA LOS ANGELES · 2022 · $380,542

## Abstract

Project summary
Charcot-Marie-Tooth disease (CMT) is a hereditary peripheral neuropathy resulting from demyelination and
axon degeneration. Many cases of axon degeneration are caused by mutations in Mitofusin-2 (Mfn2), which is
one of two dynamin-like proteins on the surface of mitochondria. Mitofusins primarily mediate mitochondrial
outer membrane fusion, but Mfn2 can also promote association between ER and mitochondria in mitochondria
associated membranes (the MAM). It is observed in spots that colocalize with the mitochondrial fission
dynamin Drp1 and it was proposed to affect axonal transport of mitochondria, raising the possibility that CMT is
caused by defects in one of these other functions of Mfn2. Preliminary data show that Mfn2 promotes
constriction of mitochondria in Drp1–/– cells and fission in Drp1-Mfn1 DKO cells when treated with the fungal
toxin PXA that causes the release of calcium from the mitochondrial matrix. Calcium release and the ability to
constrict mitochondria was linked to Mfn2-mediated regulation of NCLX (a Ca/Na exchanger in the
mitochondrial inner membrane). It is hypothesized that PXA activates NCLX and that Mfn2 is required for this
activity. It is also hypothesized that NCLX-mediated calcium release causes mitochondrial constriction and that
the effects of Mfn2 on mitochondrial fission are linked to axonal transport, a process that could be disrupted in
CMT patients. These hypotheses will be tested by investigating three aims. Aim 1. Investigate connections
between PXA, NCLX, and Mfn2. These studies will include comprehensive tests whether PXA triggers
calcium release from mitochondria by activating NCLX and investigates of the control of NCLX by Mfn2. Aim 2.
Investigate connections between Mfn2 and mitochondrial fission. Effects of Mfn2 and NCLX on
mitochondrial fission will be tested with knockout cell lines and transfections of fission and fusion protein
constructs followed by analyses with a range of imaging techniques. Aim 3. Investigate the physiological
consequences of Mfn2 and NCLX contributions to fission. Effects on mitochondrial transport proteins will
be examined with kymographs of axonal processes in cultured neurons and zebrafish. Alternative functions,
such effects on metabolism and a role in mitophagy, will also be considered. Together, these experiments will
help establish NCLX as the target of PXA, assess the newly proposed role of Mfn2 in mitochondrial fission, and
test possible downstream effects on transport or mitophagy. These experiments may therefore reveal a novel
function for Mfn2 and shed new light on the underlying causes of CMT. Possible downstream effects of fission
on axonal transport will change the understanding of the underlying causes of CMT and may suggest novel
treatment strategies.

## Key facts

- **NIH application ID:** 10322143
- **Project number:** 5R01NS120690-02
- **Recipient organization:** UNIVERSITY OF CALIFORNIA LOS ANGELES
- **Principal Investigator:** Carla M Koehler
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $380,542
- **Award type:** 5
- **Project period:** 2021-01-01 → 2025-12-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10322143

## Citation

> US National Institutes of Health, RePORTER application 10322143, Control of calcium flux and mitochondrial fission by the Charcot Marie Tooth disease protein Mfn2. (5R01NS120690-02). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10322143. Licensed CC0.

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