Mitochondrial dynamics refers to the continuous processes of mitochondrial fission (division) and fusion (joining), which maintain mitochondrial quality and function. In Parkinson's disease, these processes are severely dysregulated, leading to fragmented mitochondria, impaired energy production, and ultimately neuronal death. Targeting the proteins controlling fission and fusion offers promising neuroprotective strategies.
Dopaminergic neurons in the substantia nigra pars compacta have particularly high energy demands and are especially vulnerable to mitochondrial dysfunction. The balance between fission and fusion is critical for:
- Maintaining mitochondrial morphology and distribution
- Ensuring adequate ATP production through oxidative phosphorylation
- Facilitating quality control via mitophagy
- Distributing mitochondria throughout neuronal processes
- Regulating calcium homeostasis
| Process |
Proteins |
Function |
Therapeutic Target |
| Fission |
Drp1 (DNM1L), Fis1, Mff, MiD49/50 |
Mitochondrial division |
Drp1 inhibitors |
| Fusion |
Mfn1, Mfn2, OPA1 |
Mitochondrial joining |
Fusion agonists |
flowchart TD
subgraph Normal_State
A["Healthy Mitochondria"] <--> B["Dynamic Balance"]
B --> C["Fission - Drp1"]
B --> D["Fusion - Mfn1/2 OPA1"]
C --> E["Proper Distribution"]
D --> E
end
subgraph PD_State
F["PD Mutations"] --> G["Excessive Fission"]
G --> H["Fragmented Mitochondria"]
H --> I["ATP Depletion"]
I --> J["ROS Production"]
J --> K["Apoptotic Susceptibility"]
K --> L["Neuronal Death"]
end
subgraph Therapeutic_Intervention
M["Drp1 Inhibitors"] --> N["Reduce Fission"]
O["Mfn Agonists"] --> P["Enhance Fusion"]
O --> P
Q["OPA1 Enhancers"] --> P
N --> R["Restore Balance"]
P --> R
R --> S["Mitochondrial Health"]
S --> T["Neuronal Protection"]
end
Drp1 (Dynamin-related protein 1) is a GTPase that catalyzes mitochondrial fission:
- Recruitment mechanism: Drp1 is recruited to mitochondria via adaptor proteins (Mff, Fis1, MiD49/50) that anchor it to the outer mitochondrial membrane
- GTP hydrolysis: Drp1 assembles into rings around mitochondria and undergoes GTP hydrolysis, causing constriction and fission
- PD dysregulation: In PD models, Drp1 is overactivated, leading to excessive fission and mitochondrial fragmentation
- Pathogenic mechanisms: Drp1 overactivation is linked to:
- PINK1/Parkin pathway dysfunction
- LRRK2 mutations
- Alpha-synuclein toxicity
- Environmental neurotoxins (MPTP, 6-OHDA)
Mitofusins (Mfn1, Mfn2) and OPA1 mediate mitochondrial fusion:
- Mfn1/Mfn2: Outer membrane fusion proteins that mediate tethering and merging of mitochondrial outer membranes
- OPA1: Inner membrane fusion protein that maintains cristae structure and inner membrane integrity
- PD dysfunction: Reduced fusion activity in PD leads to impaired mitochondrial networks and quality control
- Therapeutic potential: Enhancing fusion can compensate for fission excess and restore mitochondrial function
Modulating mitochondrial dynamics can:
- Restore mitochondrial morphology: Normalize fission/fusion balance
- Improve energy production: Enhance oxidative phosphorylation efficiency
- Enhance quality control: Improve mitophagy efficiency and mitochondrial turnover
- Protect against neurotoxins: Confer resistance to MPTP, 6-OHDA, and other PD insults
- Reduce oxidative stress: Decrease ROS production from dysfunctional mitochondria
| Compound |
Company/Group |
Development Stage |
Notes |
| Mdivi-1 |
Various Academic |
Preclinical |
Widely used research tool, not brain-penetrant |
| P110 |
Academic |
Research |
Peptide-based Drp1 inhibitor |
| Drp1i |
Academic |
Discovery |
Improved CNS penetration |
| Dynasore |
Research |
Tool compound |
Not drug-like, broad GTPase inhibition |
| DDR1-IN-1 |
Industry |
Lead Optimization |
Selective Drp1 inhibitor |
Mechanism of action: Drp1 inhibitors work by:
- Blocking GTPase activity of Drp1
- Preventing mitochondrial recruitment
- Reducing excessive fission
- Restoring network morphology and function
| Approach |
Group |
Development Stage |
Target |
| SIRT1 activators |
Academic |
Preclinical |
Mfn1/2 expression via deacetylation |
| OPA1 agonists |
Industry |
Discovery |
OPA1 activation |
| Mfn1/2 gene therapy |
Academic |
Preclinical |
AAV-mediated overexpression |
| Bezafibrate |
Academic |
Preclinical |
PGC-1α activation, enhances fusion |
- Phosphorylation modulators: Targeting Drp1 phosphorylation at Ser616 (pro-fission) or Ser637 (anti-fission)
- Allosteric modulators: Targeting protein-protein interactions between Drp1 and its adaptors
- Small molecule Mfn agonists: Direct activators of mitofusin proteins
- Drp1 inhibition protects dopaminergic neurons against MPTP toxicity
- Mfn1 overexpression rescues mitochondrial dysfunction in PINK1 knockdown cells
- OPA1 enhancement improves mitochondrial function in alpha-synuclein models
| Model |
Intervention |
Outcome |
| MPTP mice |
Mdivi-1 |
Reduced dopaminergic neuron loss |
| 6-OHDA rats |
Drp1 siRNA |
Improved motor behavior |
| α-synuclein transgenic |
Mfn1 overexpression |
Reduced pathology |
| PINK1 knockout |
Drp1 inhibition |
Restored mitochondrial function |
No mitochondrial dynamics modulators are currently in PD clinical trials. This remains an important area for drug development.
- Brain penetration: Many Drp1 inhibitors fail to reach therapeutic concentrations in the CNS
- Selectivity: Off-target effects can complicate therapeutic windows
- Therapeutic window: Narrow margin between efficacy and toxicity
- Timing: Optimal intervention window in disease progression unclear
- Biomarkers: Lack of biomarkers for target engagement
- Development of brain-penetrant Drp1 inhibitors
- Exploration of combination therapies targeting multiple aspects of mitochondrial dysfunction
- Identification of patient subsets who may benefit most from mitochondrial targeting
The PINK1/PARKIN mitophagy pathway requires proper mitochondrial dynamics:
- Excessive fission impairs PINK1 accumulation on damaged mitochondria
- Restoring dynamics enhances mitophagy efficiency
- Combined targeting may provide synergistic benefit
LRRK2 mutations affect mitochondrial function:
- LRRK2 regulates Drp1 localization and activity
- Combined approaches targeting both LRRK2 and mitochondrial dynamics may enhance benefit
GBA mutations impair lysosomal function:
- Lysosomal dysfunction affects mitochondrial quality control
- Mitochondrial dynamics modulators may help compensate
- Mitochondrial morphology: Live cell imaging of neurons
- Drp1 phosphorylation: p-Ser616 Drp1 levels in blood/CSF
- ATP production: Seahorse analysis of cellular respiration
- ROS levels: MitoSOX imaging in patient-derived cells
- Development of brain-penetrant Drp1 inhibitors with optimal pharmacokinetics
- Validation of biomarkers for target engagement
- Exploration of combination therapy approaches
- Identification of patient subsets most likely to benefit
- Early-stage patients likely to benefit most
- Biomarker-enriched enrollment
- Extended treatment duration to assess disease modification