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Beclin 1 Interacts With Active Caspase-3 and Bax in Oocytes From Atretic Follicles in the Rat Ovary
María L Escobar1, Olga M Echeverria1, Sebastián Palacios-Martínez1
1Lab. Microscopía Electrónica, Departamento de Biología Celular, Facultad de Ciencias, Universidad Nacional Autónoma de México, Ciudad de México, México.
Abstract:
Oocyte cell death is a normal process in the mammalian ovary during follicular growth. Recent reports have demonstrated the presence of pro-apoptotic and pro-autophagic proteins during oocyte elimination. The goal of this study was to identify the interactions between proteins involved in different types of programmed cell death in the same oocyte during follicular atresia. We evaluated the presence of Beclin 1 and its interaction with the pro-apoptotic proteins active caspase-3, Bax, and Bak by means of histochemical observations, ultrastructural immunodetection, and immunoprecipitation techniques in ovaries from prepubertal (28- and 33-day-old), juvenile (40-day-old), and young adult (90-day-old) rats. In this study, we identified that oocyte elimination occurred with a high quantity of pro-autophagic protein Beclin 1 and increased the presence of the pro-apoptotic proteins active caspase-3, Bax, and Bak. Conversely, the antiapoptotic protein Bcl-2 was reduced in oocytes from atretic follicles. In addition, Beclin 1 was shown to interact with active caspase-3 and Bax. Our results suggest that the increase in Beclin 1 is directly related to the rise of pro-apoptotic proteins, which could promote the apoptotic process during oocyte elimination.
Insights
Oocyte elimination involves programmed cell death pathways. This study reveals Beclin 1 interacts with pro-apoptotic proteins, suggesting a link between autophagy and apoptosis during follicular atresia in rats.
Area of Science:
- Reproductive Biology
- Cellular Biology
- Developmental Biology
Background:
- Oocyte cell death is a natural part of mammalian ovarian follicular growth.
- Both pro-apoptotic and pro-autophagic proteins are implicated in oocyte elimination.
- Understanding the interplay of cell death mechanisms in oocytes is crucial.
Purpose of the Study:
- To investigate the interactions between proteins governing different programmed cell death types within the same oocyte.
- To examine these interactions during follicular atresia in rat ovaries across different age groups.
Main Methods:
- Histochemical observations
- Ultrastructural immunodetection
- Immunoprecipitation techniques
- Ovarian tissue analysis from prepubertal, juvenile, and young adult rats.
Main Results:
- Oocyte elimination correlated with high levels of the pro-autophagic protein Beclin 1.
- Increased presence of pro-apoptotic proteins (active caspase-3, Bax, Bak) was observed.
- The anti-apoptotic protein Bcl-2 was reduced, and Beclin 1 interacted with active caspase-3 and Bax.
Conclusions:
- Elevated Beclin 1 levels are directly associated with increased pro-apoptotic proteins during oocyte elimination.
- These interactions suggest a coordinated apoptotic process driven by Beclin 1 and pro-apoptotic factors.
- The findings provide insight into the molecular mechanisms of oocyte programmed cell death in follicular atresia.
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