Abstract
Purpose :
Mitochondria, the energy powerhouse of the cell, undergo dynamic mitochondrial fusion/fission, biogenesis and mitophagy in response to physiological stimuli or pathological stresses. Disruption of mitochondrial homeostasis could lead to cellular phenotypes including death or senescence. While mitochondria-mediated cell death is well-studied, the mechanism whereby defective mitochondrial dynamics induces cellular senescence remains unclear. The purpose of the project is to explore whether and how PGAM5 plays a role in RPE senescence.
Methods :
PGAM5 knockout mice and PGAM5 -/- RPE cells generated using CRISPR-Cas9 system are used to study the function of PGAM5. The change in AMPK-mTOR signaling and immune regulatory pathways was examined by Western blot and immunostaining. Mitochondrial fusion/fission dynamics were examined in vitro. Cellular senescence was examined by β-gal staining, and measuring p16, Macro-H2A and p-rH2A levels, as well as the senescence-associated secretory phenotypes (SASP). Drp1 phosphorylation was explored as a mechanism of PGAM5 function, and Drp1K38A mutant overexpression was used to mimic PGAM5 loss-of-function in vitro. The resistance of PGAM5 knockout mice to oxidative stress during aging was examined by histological staining.
Results :
We found that: (1) PGAM5 deletion leads to accelerated senescence in vitro and in mice; (2) PGAM5 deletion leads to changes in mitochondrial morphology and dynamics, leading to mitochondrial hyperfusion, less mitochondrial turnover and biogenesis, and retarded mitophagy; (3) PGAM5 deletion leads to activation of mTOR and IRF/IFN-b pathways, which are essential pathways for senescence; (4) Drp1-K38A overexpression mimics the mitochondrial morphology change, mTOR activation and senescence in PGAM5-/- RPE cells; (5) PGAM5 deletion renders RPE cells resistance to oxidative stress, which is lost during aging.
Conclusions :
These data establish a link between PGAM5, mitochondrial fission, mitophagy, senescence and anti-oxidative response, reinforcing the importance of mitochondrial dynamics in regulating cellular senescence (Supported by NIH grants EY021862 and EY026069)
This is a 2020 ARVO Annual Meeting abstract.