# Mitochondrial calcium overload and necrosis in tauopathies caused by inhibition of Mfn2 and NCLX

> **NIH NIH R01** · UNIVERSITY OF CALIFORNIA LOS ANGELES · 2023 · $390,000

## Abstract

Abstract
Tau aggregates (also known as neurofibrillary tangles or NFTs) are hallmarks of the neurodegenerative
diseases collectively known as tauopathies. These diseases are a broad class of a dozen or more dementias
that include the frontotemporal dementias, Pick’s disease, and chronic traumatic encephalopathy. Alzheimer’s
is also a tauopathy, even though this disease is best known for the formation of amyloid plaques. In this case,
the extracellular amyloid plaques induce intracellular tau aggregation. The formation of tau aggregates is
preceded by tau oligomerization, which is considered the primary cause of toxicity, ultimately inducing cell
death. Several recent papers suggest that tau oligomers or aggregates inhibit calcium release from
mitochondria, which then triggers cell death through necrosis by opening of the mitochondrial permeability
transition pore (MPTP). The target of this inhibition is the Na+/Ca2+ exchanger NCLX, which is localized to the
mitochondrial inner membrane. It is unclear how cytosolic tau oligomers and aggregates interfere with NCLX
function because of their different cellular locations. Data from the parent grant of this supplement provides a
potential mechanism for inhibition. These data show that NCLX on the mitochondrial inner membrane is
controlled by Mfn2 on the outer membrane. Mfn2 is one of two mitochondrial outer membrane fusion proteins,
but it also plays a role in tethering of mitochondria to the endoplasmic reticulum where calcium exchange is
important for regulating mitochondrial functions. The parent grant focuses on the effects that the connection
between Mfn2 and NCLX have on a peripheral neuropathy (the Charcot Marie Tooth disease CMT2A), and
investigates the possibility that CMT2A is caused by excessive Ca2+ release into the cytosol through overactive
NCLX. Here, we hypothesize that cytosolic tau oligomers or tau aggregates have the opposite effect, causing
cell death by loss of NCLX function, and that this toxicity is mediated by interference with Mfn2 function. The
resulting Ca2+ overload in mitochondria can then cause necrosis by opening MPTP. In this scenario, Mfn2
would provide a bridge between the cytosol, which is where tau aggregates are localized, and NCLX on the
inner membrane. The aim of this supplement is therefore to determine whether the toxicity of tau oligomers or
aggregates is due to calcium overload in mitochondria and if this overload is caused by interference with Mfn2
and its downstream effector NCLX. The effects of tau oligomers and aggregates on Mfn2/NCLX-mediated Ca2+
release and cell death will first be investigated using an existing cultured cell model for tauopathies (HEK293
sensor cells) and then with increasingly more complex systems (differentiated neurons and Zebrafish) in
preparation for submitting an R01 with mouse models. The discovery of this novel pathway for tau-induced
toxicity also provides new targets for drug treatment (Mfn2 and NCLX). Pilot experiments with ...

## Key facts

- **NIH application ID:** 10714837
- **Project number:** 3R01NS120690-03S1
- **Recipient organization:** UNIVERSITY OF CALIFORNIA LOS ANGELES
- **Principal Investigator:** Carla M Koehler
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2023
- **Award amount:** $390,000
- **Award type:** 3
- **Project period:** 2021-01-01 → 2023-12-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10714837

## Citation

> US National Institutes of Health, RePORTER application 10714837, Mitochondrial calcium overload and necrosis in tauopathies caused by inhibition of Mfn2 and NCLX (3R01NS120690-03S1). Retrieved via AI Analytics 2026-05-26 from https://api.ai-analytics.org/grant/nih/10714837. Licensed CC0.

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