Mitochondrial fission and fusion mediators, hFis1 and OPA1, modulate cellular senescence

Area of Science:

• Cell Biology
• Mitochondrial Dynamics
• Cellular Senescence

Background:

• Mitochondrial morphology is regulated by fission and fusion.
• The human protein hFis1 (human fission protein 1) is involved in mitochondrial fission.
• Dysregulation of mitochondrial dynamics is linked to cellular dysfunction.

Purpose of the Study:

• To investigate the role of hFis1 in regulating mitochondrial morphology and cellular senescence.
• To determine the consequences of hFis1 depletion on mitochondrial dynamics and cell phenotype.
• To explore the relationship between mitochondrial elongation and senescence.

Main Methods:

• Reduced hFis1 expression in mammalian cells using short hairpin RNA (shRNA).
• Assessed mitochondrial morphology, cell size, granularity, and proliferation rates.
• Measured senescence-associated beta-galactosidase activity.
• Utilized gene reintroduction and depletion of OPA1 (a fusion protein) to study rescue effects.

Main Results:

• hFis1 depletion led to sustained mitochondrial elongation, cellular enlargement, flattening, and increased granularity.
• Cells lacking hFis1 exhibited elevated senescence markers and reduced proliferation.
• Reintroducing hFis1 restored mitochondrial fragmentation and suppressed senescence.
• Simultaneous depletion of hFis1 and OPA1 caused mitochondrial fragmentation and rescued senescence phenotypes.
• Mitochondrial elongation correlated with decreased membrane potential, increased reactive oxygen species (ROS), and DNA damage.

Conclusions:

• Sustained mitochondrial elongation induces senescence-associated phenotypic changes.
• Mitochondrial fission, mediated by hFis1, prevents senescence by counteracting excessive elongation.
• hFis1 plays a critical role in maintaining mitochondrial homeostasis and preventing cellular senescence.