# Degradation of Mitochondrial Inner Membrane Protein Disrupts the Structural Interaction between Mitofilin and Cyclophilin D and Determines the Extent of Ischemia/reperfusion injury

> **NIH NIH R01** · UNIVERSITY OF TEXAS HLTH SCIENCE CENTER · 2020 · $377,575

## Abstract

Disorders characterized by ischemia/reperfusion (I/R), such as myocardial infarction, stroke, and
peripheral vascular disease, continue to be among the most frequent causes of devastating disease and main
causes of death in the US. Reperfusion of ischemic tissue triggers many pro-death signaling pathways which
converge on to the mitochondria. Indeed, reoxygenation of cardiomyocytes leads to mitochondrial Ca2+
overload and an increase in reactive oxygen species (ROS) generation that triggers the opening of the
mitochondrial permeability transition pore (mPTP). Although several proteins have been proposed as
contributing to mPTP formation and function, its exact molecular identity and mechanism still need to be
elucidated. Therefore, the current proposal seeks to establish the impact of mitofilin, which controls
mitochondrial cristae morphology, regulation in mPTP formation that is responsible for triggering mitochondrial
permeability transition is of fundamental importance for advancing our basic understanding of the mechanisms
of I/R injury and represents a particularly exciting approach that will open new possibilities for therapeutic
interventions against various diseases including I/R injury. Using 2D-DIGE and mass spectrometry, we
identified mitofilin as a protein whose expression is significantly reduced after I/R versus sham. We found that
versus WT, mitofilin-/- mice subjected to I/R exhibit an increase in myocardial infarct size, a reduction in cardiac
functional recovery and Ca2+ retention capacity required to induce the mPTP opening, as well as an increase in
mitochondrial Parkin expression and mitofilin ubiquitination. We further found that knockdown of mitofilin in
H9c2 myoblasts with siRNA led to an increase in apoptosis via the AIF-PARP1 pathway that is associated with
S phase arrest of the cell cycle, an increase in mitochondrial cristae disorganization, ROS production and
Calpain activity, as well as a decrease in intracellular ATP production and mitochondrial membrane potential
versus scramble siRNA. Interestingly, we also revealed that mitofilin structurally binds to Cyclophilin D and this
interaction is abridged after mPTP opening triggered by Ca2+ overload. Our central hypothesis is that
degradation mitofilin during I/R disrupts the CypD-mitofilin interaction resulting in pore formation that triggers
mitochondrial permeability transition, thus activating necrotic signaling cascades. We will: 1) Define whether
protection of mitofilin from degradation induces protective effects against I/R injury and anti-inflammatory
effects in vivo, as well as establish the mechanism by which mitofilin down-regulation promotes apoptosis in
transfected H9c2 myoblasts; 2. Define the impact of the MEK/ERK/GSK-3 pathway in I/R-induced mitofilin
degradation, and reveal the mechanisms by which I/R stress induces mitofilin loss by increasing mitofilin
ubiquitination, promoting excessive mitophagy, and increasing Calpain activity; 3. Determine the im...

## Key facts

- **NIH application ID:** 9933987
- **Project number:** 5R01HL138093-04
- **Recipient organization:** UNIVERSITY OF TEXAS HLTH SCIENCE CENTER
- **Principal Investigator:** Jean Chrisostome Bopassa
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $377,575
- **Award type:** 5
- **Project period:** 2017-07-15 → 2022-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9933987

## Citation

> US National Institutes of Health, RePORTER application 9933987, Degradation of Mitochondrial Inner Membrane Protein Disrupts the Structural Interaction between Mitofilin and Cyclophilin D and Determines the Extent of Ischemia/reperfusion injury (5R01HL138093-04). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/9933987. Licensed CC0.

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