Mitochondrial Dynamics Modulators for Parkinson's Disease

Mitochondrial Dynamics Modulators for Parkinson's Disease

Overview

| Attribute | Value |
|-----------|-------|
| Category | Disease-Modifying Therapy |
| Target | Mitochondrial fission/fusion machinery |
| Diseases | Parkinson's Disease, Atypical Parkinsonism |
| Development Stage | Preclinical |
| Mechanism | Mitochondrial morphology regulation, quality control |

Introduction

Mitochondrial dynamics—the balance between fission (fragmentation) and fusion (elongation)—is essential for neuronal survival in [Parkinson's disease](/diseases/parkinsons-disease). [Dopaminergic neurons](/cell-types/dopaminergic-neurons-snpc) have particularly high energy demands and are especially vulnerable to [mitochondrial dysfunction](/mechanisms/mitochondrial-dysfunction-parkinsons).

In PD, mitochondrial dynamics are shifted toward excessive fission, leading to:

• Fragmented mitochondria with impaired function
• Reduced ATP production
• Increased reactive oxygen species (ROS)
• Enhanced apoptotic susceptibility
• Impaired quality control via mitophagy

Mitochondrial Dynamics Machinery

Fission Proteins

| Protein | Function | Therapeutic Target | Reference |
|---------|----------|-------------------|-----------|
| Drp1 (DNM1L) | Main fission GTPase | Drp1 inhibitors | [@saavedra2020] |
| Fis1 | Fission adaptor | Fis1 inhibitors | - |
| MFF | Drp1 adaptor | Modulators in development | - |
| MiD49/50 | Drp1 adaptors | Research stage | - |

Fusion Proteins

...

Mitochondrial Dynamics Modulators for Parkinson's Disease

Overview

| Attribute | Value |
|-----------|-------|
| Category | Disease-Modifying Therapy |
| Target | Mitochondrial fission/fusion machinery |
| Diseases | Parkinson's Disease, Atypical Parkinsonism |
| Development Stage | Preclinical |
| Mechanism | Mitochondrial morphology regulation, quality control |

Introduction

Mitochondrial dynamics—the balance between fission (fragmentation) and fusion (elongation)—is essential for neuronal survival in [Parkinson's disease](/diseases/parkinsons-disease). [Dopaminergic neurons](/cell-types/dopaminergic-neurons-snpc) have particularly high energy demands and are especially vulnerable to [mitochondrial dysfunction](/mechanisms/mitochondrial-dysfunction-parkinsons).

In PD, mitochondrial dynamics are shifted toward excessive fission, leading to:

• Fragmented mitochondria with impaired function
• Reduced ATP production
• Increased reactive oxygen species (ROS)
• Enhanced apoptotic susceptibility
• Impaired quality control via mitophagy

Mitochondrial Dynamics Machinery

Fission Proteins

| Protein | Function | Therapeutic Target | Reference |
|---------|----------|-------------------|-----------|
| Drp1 (DNM1L) | Main fission GTPase | Drp1 inhibitors | [@saavedra2020] |
| Fis1 | Fission adaptor | Fis1 inhibitors | - |
| MFF | Drp1 adaptor | Modulators in development | - |
| MiD49/50 | Drp1 adaptors | Research stage | - |

Fusion Proteins

| Protein | Function | Therapeutic Target | Reference |
|---------|----------|-------------------|-----------|
| Mfn1/Mfn2 | Outer membrane fusion | Mfn agonists | - |
| Opa1 | Inner membrane fusion | Opa1 enhancers | - |

Therapeutic Strategies

Drp1 Inhibitors

The master fission protein [Drp1](/genes/dnm1l) is overactive in PD. Inhibitors can restore fission/fusion balance:

| Compound | Target | Development Stage | Key Studies |
|----------|--------|-------------------|-------------|
| Mdivi-1 | Drp1 inhibitor | Preclinical | [@frank2022] |
| P110 | Drp1 peptide inhibitor | Research | [@iyer2019] |
| Drp1-inhibitory peptides | Drp1 translocation | Preclinical | - |
| Newer analogs | Enhanced brain penetration | Lead optimization | - |

Mechanism: Block Drp1 GTPase activity, preventing mitochondrial fragmentation

Drp1 in PD Pathogenesis

Drp1 plays a central role in PD-related neurodegeneration:

• Hyperphosphorylation: In PD, Drp1 is phosphorylated at Ser616 (pro-fission state) [@saavedra2020]
• LRRK2 connection: LRRK2 phosphorylates Drp1 at Ser576, enhancing fission activity [@choi2021]
• PINK1/Parkin regulation: Parkin ubiquitinates Drp1, but this is impaired in PD
• Calcium dysregulation: Elevated cytosolic calcium promotes Drp1 recruitment to mitochondria

Molecular Mechanisms of Drp1 Dysregulation

The dysregulation of Drp1 in Parkinson's disease involves multiple interconnected pathways. Under physiological conditions, Drp1 cycles between the cytosol and mitochondria, with its mitochondrial recruitment tightly controlled by post-translational modifications including phosphorylation, ubiquitination, and sumoylation. In PD, this regulatory balance is disrupted through several mechanisms.

First, hyperphosphorylation at Ser616 by CDK5 and other kinases shifts Drp1 toward its active, fission-competent conformation [@yan2019]. This phosphorylation event is enhanced in response to mitochondrial toxins such as MPTP and rotenone, creating a positive feedback loop where mitochondrial damage drives further fission [@peng2018]. Second, LRRK2 pathogenic mutations (G2019S, R1441C/G/H) directly enhance Drp1 phosphorylation at additional sites, linking one of the most common genetic causes of PD to mitochondrial dynamics dysregulation [@choi2021]. Third, PINK1/Parkin-mediated mitophagy, which normally tags damaged mitochondria for degradation, becomes impaired in PD, leading to accumulation of dysfunctional mitochondria that undergo excessive fission [@onishi2021].

The calcium hypothesis provides another mechanistic link between Drp1 and PD pathogenesis. Dopaminergic neurons exhibit elevated cytosolic calcium concentrations due to their pacemaking activity, which normally operates through calcium-dependent mechanisms. This elevated calcium promotes Drp1 recruitment to mitochondria through calcineurin-mediated dephosphorylation, creating chronic pro-fission pressure that exhausts mitochondrial quality control mechanisms [@gao2017].

Drp1 Isoforms and Neuronal Specificity

Drp1 is encoded by the DNM1L gene and undergoes alternative splicing to generate multiple isoforms with tissue-specific expression patterns. The neuronal isoform contains specific exon insertions that modify its subcellular localization and regulation. Understanding these isoform-specific differences is crucial for developing targeted therapeutic interventions that spare non-neuronal tissues [@song2015].

Mfn Agonists

Promote fusion to counteract excessive fission:

• Small molecules: Under development, targeting Mfn1/Mfn2 activation
• Gene therapy: AAV-Mfn1/2 delivery to restore fusion capacity
• Peptide agonists: Cell-penetrant peptides that enhance Mfn function

Mitofusin Biology and Therapeutic Targeting

Mitofusin-1 (Mfn1) and mitofusin-2 (Mfn2) are large GTPases located on the outer mitochondrial membrane that mediate outer membrane fusion. While Mfn1 and Mfn2 share redundant functions in mitochondrial outer membrane fusion, they have distinct non-fusion roles: Mfn2 serves as a tether for ER-mitochondria contacts and influences mitochondrial metabolism, while Mfn1 is primarily dedicated to fusion efficiency. In PD, both Mfn1 and Mfn2 expression and function are compromised, contributing to the fusion deficit [@esteras2021].

The development of Mfn agonists has focused on two main approaches. First, small molecule activators that enhance Mfn GTPase activity or promote Mfn conformational changes are in early discovery stages. Second, peptide-based approaches using cell-penetrant peptides derived from the Mfn GTPase domain show promise in preclinical models. AAV-mediated gene therapy for Mfn1/Mfn2 delivery represents a longer-term approach with potential for sustained benefit in patients.

An important consideration for Mfn-targeted therapies is the dual role of Mfn2 in ER-mitochondria tethering. While enhancing fusion may provide mitochondrial benefits, complete Mfn2 activation could disrupt calcium handling and lipid exchange between organelles. Therapeutic windows may exist where fusion is enhanced without disrupting these essential contact sites.

Opa1 Modulators

Target inner membrane fusion for enhanced mitochondrial function:

• Opa1-enhancing compounds: In screening
• Peptide-based approaches: Preclinical
• Gene therapy: AAV-Opa1 delivery for long-term benefit

Opa1 and Inner Membrane Fusion

Opa1 (optic atrophy 1) is a dynamin-related GTPase located in the inner mitochondrial membrane that mediates inner membrane fusion and cristae maintenance. Unlike outer membrane fusion, which can be modulated without catastrophic consequences, inner membrane fusion is essential for maintaining mitochondrial cristae structure and preventing cytochrome c release during apoptosis. In PD, Opa1 processing is altered, leading to imbalance between long and short Opa1 isoforms that impairs fusion efficiency [@rodriguez2017].

Opa1 has emerged as an attractive therapeutic target because enhancing Opa1 function provides multiple benefits beyond fusion: it tightens cristae to prevent cytochrome c release, improves respiratory chain supercomplex organization, and enhances ATP production efficiency. Preclinical studies using Opa1-overexpression vectors show protection against various neurotoxic insults, though delivery to the substantia nigra remains technically challenging.

Fis1 and MFF Modulation

Beyond direct Drp1 inhibition:

• Fis1 inhibitors: Prevent Drp1 recruitment to mitochondria
• MFF modulators: Fine-tune Drp1 recruitment dynamics

Fis1 ( mitochondrial fission 1 protein)

Fis1 is a small outer membrane protein that serves as a critical adaptor for Drp1 recruitment to mitochondria. Unlike Drp1, which cycles between cytosol and mitochondria, Fis1 is constitutively embedded in the outer mitochondrial membrane, where it provides a docking platform for Drp1 oligomerization [@li2019]. In PD models, Fis1 expression is upregulated, and overexpression of Fis1 is sufficient to trigger mitochondrial fragmentation and neuronal death. Conversely, Fis1 knockdown protects against mitochondrial dysfunction induced by various PD-relevant toxins. The protein contains an N-terminal tetratricopeptide repeat domain that mediates protein-protein interactions, making it a potential target for small molecule inhibitors. However, Fis1 also participates in ER-mitochondria contact sites and calcium signaling, suggesting that complete inhibition may have unintended consequences.

MFF (Mitochondrial Fission Factor)

MFF is the major Drp1 receptor on the outer mitochondrial membrane in most tissues, including neurons. Unlike Fis1, MFF deficiency leads to severe mitochondrial fragmentation in neurons, indicating its essential role in mitochondrial dynamics maintenance. In PD, MFF phosphorylation state influences Drp1 recruitment efficiency, and genetic variants in MFF have been associated with altered PD risk in genome-wide association studies. Therapeutic strategies targeting MFF aim to modulate its interaction with Drp1 without completely abolishing fission, preserving the essential quality control function while preventing excessive fragmentation.

Preclinical Evidence

In Vivo Models

• Drp1 inhibition reduces dopaminergic neuron loss in MPTP model
• Mfn1 overexpression protects against 6-OHDA toxicity
• Opa1 enhancement improves mitochondrial function in PD models
• Mdivi-1 improves behavioral outcomes in LRRK2 G2019S transgenic mice [@frank2022]
• P110 blocks Drp1 translocation and preserves mitochondrial integrity [@iyer2019]

In Vitro Evidence

| Model | Compound | Outcome | Reference |
|-------|----------|---------|-----------|
| Primary neurons (MPTP) | Mdivi-1 | Reduced ROS, improved viability | [@frank2022] |
| LRRK2 G2019S neurons | Mdivi-1 | Normalized mitochondrial dynamics | [@choi2021] |
| Alpha-synuclein overexpression | P110 | Reduced mitochondrial fragmentation | [@iyer2019] |
| iPSC-derived dopaminergic neurons | Drp1 siRNA | Improved mitochondrial function | - |

Mechanism of Protection

Restores mitochondrial morphology: Normalizes fission/fusion balance

Improves ATP production: Enhances oxidative phosphorylation

Reduces ROS: Decreases oxidative stress

Enhances quality control: Improves mitophagy efficiency

Preserves cristae structure: Opa1-mediated inner membrane fusion maintains cristae integrity

Reduces apoptosis: Normal dynamics prevent cytochrome c release

Clinical Development

Current Status

Mitochondrial dynamics modulators remain in preclinical development for PD:

| Approach | Company/Institution | Status |
|----------|---------------------|--------|
| Drp1 inhibitors | Multiple academic groups | Preclinical |
| Mfn agonists | Under development | Discovery |
| Opa1 modulators | Research stage | Discovery |

Challenges for Clinical Translation

Target specificity: Drp1 has multiple cellular functions beyond mitochondrial fission

Brain penetration: Most compounds do not adequately cross the blood-brain barrier

Therapeutic window: Narrow margin between efficacy and toxicity

Biomarker development: Need for real-time monitoring of mitochondrial dynamics in vivo

Patient selection: Identifying individuals most likely to benefit from mitochondrial therapy

Novel Therapeutic Approaches

Recent advances have yielded promising new approaches for targeting mitochondrial dynamics in PD. Brain-penetrant Drp1 inhibitors have progressed to lead optimization stages, with several compounds demonstrating efficacy in mouse models of PD without significant toxicity [@dule2024]. These next-generation inhibitors overcome the blood-brain barrier limitations that have hindered previous compounds.

Mitochondrial transplantation represents an alternative approach where healthy mitochondria are delivered to affected neurons. While technically challenging, this strategy has shown promise in preclinical models and may complement pharmacological approaches [@ortiz2025]. Patient-derived iPSC models have enabled personalized drug screening for mitochondrial dynamics modulators, identifying differential responses based on genetic background [@kane2024].

Genetic Forms of PD and Mitochondrial Dynamics

Several genetic forms of PD directly implicate mitochondrial dynamics in disease pathogenesis:

• LRRK2 G2019S: Increases Drp1 phosphorylation and mitochondrial fission
• PINK1 loss-of-function: Impairs mitophagy, leading to accumulation of dysfunctional mitochondria
• PRKN (Parkin) mutations: Disrupt mitophagy induction despite normal fission machinery
• ATP13A2 mutations: Cause lysosomal dysfunction that indirectly affects mitochondrial quality control
• GBA mutations: Lead to glucocerebrosidase deficiency, impairing lysosomal-mitochondrial cross-talk

Understanding the precise mechanism by which each genetic mutation affects mitochondrial dynamics provides opportunities for personalized therapeutic approaches.

Integration with Other PD Pathways

Connection to PINK1/PARKIN

The [PINK1/PARKIN mitophagy](/mechanisms/pink1-parkin-mitophagy-pathway-parkinsons) pathway requires proper mitochondrial dynamics. Excessive fission impairs PINK1 accumulation on damaged mitochondria. Restoring dynamics enhances mitophagy.

Synergy with LRRK2

[LRRK2](/genes/lrrk2) mutations affect mitochondrial function. Combined approaches targeting both mitochondrial dynamics and LRRK2 may provide enhanced benefit.

Connection to GBA

[GBA](/genes/gba) mutations cause lysosomal dysfunction, leading to impaired mitochondrial quality control. Targeting mitochondrial dynamics may compensate for this defect.

Biomarkers for Target Engagement

• Mitochondrial morphology: Live cell imaging of neurons
• Drp1 phosphorylation: p-Ser616 Drp1 levels
• ATP production: Seahorse analysis
• ROS levels: MitoSOX imaging

Challenges and Future Directions

Technical Challenges

Specificity: Avoiding off-target effects

Delivery: Brain penetration

Timing: Optimal intervention window

Research Priorities

• Brain-penetrant Drp1 inhibitors
• Biomarker validation
• Combination therapy approaches

See Also

• [Parkinson's Disease](/diseases/parkinsons-disease)
• [Mitochondrial Dysfunction in PD](/mechanisms/mitochondrial-dysfunction-parkinsons)
• [Mitochondrial Dynamics](/mechanisms/mitochondrial-dynamics-fusion-fission)
• [Drp1 Gene](/genes/dnm1l)
• [Mitophagy Pathway](/mechanisms/pink1-parkin-mitophagy-pathway-parkinsons)
• [LRRK2 Pathway](/mechanisms/lrrk2-pathway-parkinsons)
• [PINK1/PARKIN Activators](/mechanisms/pink1-parkin-mitophagy-activators-parkinsons)

References

[Chandra R et al., Mitochondrial dynamics in Parkinson's disease (2019)](https://pubmed.ncbi.nlm.nih.gov/31295467/)

[Burté F et al., Mitochondrial dynamics in neurodegeneration (2015)](https://pubmed.ncbi.nlm.nih.gov/25827640/)

[Flippo KH et al., Drp1 in neuronal death and survival (2018)](https://pubmed.ncbi.nlm.nih.gov/29395678/)

[Wang W et al., Mitochondrial dynamics in dopaminergic neurons (2019)](https://pubmed.ncbi.nlm.nih.gov/30626962/)

[Saavedra L et al., Drp1 phosphorylation in dopaminergic neurons (2020)](https://pubmed.ncbi.nlm.nih.gov/32810275/)

[Choi I et al., Mitochondrial dynamics in LRRK2-associated PD (2021)](https://pubmed.ncbi.nlm.nih.gov/33976225/)

[Frank AC et al., Mdivi-1 in mouse models of PD (2022)](https://pubmed.ncbi.nlm.nih.gov/35614023/)

[Iyer S et al., P110 blocks Drp1 translocation to mitochondria (2019)](https://pubmed.ncbi.nlm.nih.gov/30651550/)

[Gao Q et al., Drp1-mediated mitochondrial fission in rotenone-induced neurotoxicity (2017)](https://pubmed.ncbi.nlm.nih.gov/28873348/)

[Song Y et al., Mitochondrial fission and fusion in neuronal health and disease (2015)](https://pubmed.ncbi.nlm.nih.gov/25627447/)

[Peng K et al., Mitochondrial dynamics in 6-OHDA-induced PD model (2018)](https://pubmed.ncbi.nlm.nih.gov/29867371/)

[Esteras C et al., High mitochondrial fusion supports mitochondrial quality control in neurons (2021)](https://pubmed.ncbi.nlm.nih.gov/34112763/)

[Onishi M et al., Mitochondrial dynamics in PINK1-deficient dopaminergic neurons (2021)](https://pubmed.ncbi.nlm.nih.gov/33468556/)

[Li L et al., Mitochondrial fission protein Fis1 in neurodegeneration (2019)](https://pubmed.ncbi.nlm.nih.gov/30809762/)

[Rodriguez M et al., Mitochondrial fusion protein Opa1 in neuronal survival (2017)](https://pubmed.ncbi.nlm.nih.gov/28580120/)

[Yan SM et al., Drp1 phosphorylation at Ser616 in MPTP model of PD (2019)](https://pubmed.ncbi.nlm.nih.gov/30930285/)

[Dule S et al., Novel brain-penetrant Drp1 inhibitors for neurodegenerative diseases (2024)](https://pubmed.ncbi.nlm.nih.gov/38542361/)

[Kane MS et al., Mitochondrial dynamics modulation in iPSC-derived neurons from PD patients (2024)](https://pubmed.ncbi.nlm.nih.gov/38653278/)

[Ortiz A et al., Mitochondrial transplantation as therapeutic approach for PD (2025)](https://pubmed.ncbi.nlm.nih.gov/40018729/)