Variable mitochondrial phenotypes and reduced complex IV assembly factor SCO2 in LRRK2-G2019S fibroblasts

Area of Science:

• Neuroscience
• Genetics
• Cell Biology

Background:

• The Leucine-Rich Repeat Kinase 2 (LRRK2) gene harbors the G2019S mutation, a frequent cause of familial Parkinson's disease (PD).
• LRRK2-G2019S exhibits incomplete penetrance, meaning not all carriers develop PD, and its underlying molecular mechanisms remain unclear.
• Mitochondrial dysfunction is implicated in PD pathogenesis, but the specific role of LRRK2 mutations in this process requires further investigation.

Purpose of the Study:

• To investigate the mitochondrial effects associated with LRRK2-G2019S penetrance.
• To compare patient-derived fibroblasts from manifesting and non-manifesting LRRK2-G2019S carriers with controls to elucidate the mutation's pathogenic mechanism.
• To identify specific molecular alterations in mitochondria linked to LRRK2-G2019S-associated PD.

Main Methods:

• Utilized patient-derived fibroblasts from manifesting and non-manifesting LRRK2-G2019S carriers and controls.
• Quantified the expression of the complex IV assembly factor SCO2 and complex IV subunits.
• Assessed unbound mitochondrial copper content, mitochondrial morphology, membrane potential, ATP production, and reactive oxygen species (ROS) generation.

Main Results:

• A significant 50% reduction in SCO2 expression was observed in manifesting LRRK2-G2019S fibroblasts, but not in non-manifesting carriers.
• Manifesting carriers showed a minor decrease in complex IV subunit expression alongside reduced SCO2.
• No significant differences in mitochondrial copper, morphology, membrane potential, ATP, or ROS levels were found between manifesting and non-manifesting carriers, indicating cellular phenotype heterogeneity.

Conclusions:

• Mitochondrial complex IV deficiency, potentially due to reduced SCO2, may be a pathogenic mechanism in LRRK2-G2019S-associated Parkinson's disease.
• The observed heterogeneity in cellular phenotypes suggests the presence of compensatory mechanisms in LRRK2-G2019S carriers.
• Further research is needed to fully understand the interplay between SCO2, complex IV function, and PD development in LRRK2 mutation carriers.