Videoaula 02 Senescência e Morte Celular

Summary

This video covers the various types of cell death, focusing on apoptosis, or programmed cell death, and its mechanisms. It explains how apoptosis plays a key role in development, such as sculpting body parts, and its importance in maintaining cellular homeostasis. The video also explores the differences between apoptosis and necrosis, the caspase cascade involved in apoptosis, and the regulatory role of the Bcl-2 protein family. Additionally, it highlights groundbreaking research on apoptosis in *Caenorhabditis elegans*, leading to key insights into diseases like cancer and neurodegenerative disorders.

Takeaways

• 😀 Apoptosis is a form of programmed cell death, distinct from other types such as necrosis, mitotic catastrophe, and autophagy.
• 😀 Apoptosis plays a crucial role in development, particularly in shaping structures like hands, feet, and facial features by eliminating unnecessary cells.
• 😀 The process of apoptosis can be triggered by both internal (intrinsic) and external (extrinsic) signals, with each pathway involving specific molecular events.
• 😀 One key feature of apoptosis is the fragmentation of DNA and condensation of chromatin, which are crucial for the subsequent cell breakdown.
• 😀 Necrosis involves the rupture of the cell membrane, leading to the leakage of cellular contents, whereas apoptotic cells maintain membrane integrity and form apoptotic bodies.
• 😀 In apoptosis, the cell's components are recycled within the body rather than forming pus, as is the case with necrosis.
• 😀 Caspases are the central enzymes in apoptosis, carrying out the cleavage and degradation of proteins, with initiator caspases activating executioner caspases to drive the process.
• 😀 The bcl-2 family of proteins plays a regulatory role in apoptosis, with pro-apoptotic and anti-apoptotic members controlling the activation of apoptosis pathways.
• 😀 The nematode *Caenorhabditis elegans* has been widely used in apoptosis research, contributing significantly to understanding programmed cell death and its genetic regulation.
• 😀 Nobel laureate Robert Horvitz's work on apoptosis in *C. elegans* identified key genes like ced-3 and ced-4, which play essential roles in regulating cell death.
• 😀 Apoptotic bodies formed during apoptosis are recognized and engulfed by phagocytic cells, ensuring the recycling of cellular components without triggering inflammation.

Q & A

What is apoptosis, and how does it differ from other forms of cell death?

Apoptosis, or programmed cell death, is a controlled process where cells undergo a series of regulated steps leading to their self-destruction. It differs from other forms of cell death like necrosis, where cells die due to external factors such as infections, resulting in inflammation. Apoptosis, in contrast, does not cause inflammation as the cell fragments into apoptotic bodies, which are then engulfed and recycled by phagocytes.

What are the main forms of cellular death discussed in the script?

The main forms of cellular death discussed are apoptosis, necrosis, mitotic catastrophe, and autophagy. Apoptosis is programmed cell death, necrosis occurs due to external damage (e.g., infection), mitotic catastrophe results from severe mitotic errors, and autophagy involves the cell digesting its own components, often in response to stress or damage.

What is the role of caspases in apoptosis?

Caspases are proteases that play a central role in apoptosis. They are activated in a cascade, where initiator caspases like caspase-9 activate effector caspases like caspase-3. These caspases cleave essential cellular proteins, leading to the breakdown of the cell’s structure and ultimately its death.

How does apoptosis contribute to the development of an organism?

Apoptosis plays a crucial role in shaping the organism during development by eliminating unnecessary or excess cells. For example, during limb development, apoptosis helps sculpt fingers and toes by removing the cells between them, ensuring the proper formation of limbs.

What is the difference between apoptosis and necrosis in terms of cellular integrity?

In apoptosis, the cell maintains membrane integrity throughout the process, with the formation of vesicles containing cellular contents, which are later recycled by phagocytes. In contrast, necrosis involves the rupture of the cell membrane, releasing intracellular contents into the surrounding tissue, which triggers an inflammatory response.

What are apoptotic bodies, and how are they removed from the body?

Apoptotic bodies are small membrane-bound vesicles formed during the fragmentation of a cell in apoptosis. These bodies contain the cell's degraded components and are recognized and engulfed by phagocytic cells, which recycle the material without causing inflammation.

What is the role of the Bcl-2 family of proteins in apoptosis regulation?

The Bcl-2 family of proteins regulates apoptosis by controlling mitochondrial integrity. Anti-apoptotic members, like Bcl-2, prevent cell death, while pro-apoptotic members, like Bax, promote apoptosis by permeabilizing the mitochondrial membrane and initiating the release of cytochrome c, which triggers the apoptotic cascade.

What is the difference between the intrinsic and extrinsic pathways of apoptosis?

The intrinsic pathway is triggered by internal signals, such as mitochondrial stress, and involves the release of cytochrome c, which activates caspase-9 and initiates apoptosis. The extrinsic pathway is triggered by external signals, typically from immune cells, and involves the binding of death ligands like FasL to cell surface receptors, activating caspase-8 and starting the apoptotic process.

What is the apoptosome, and what is its role in apoptosis?

The apoptosome is a protein complex formed when cytochrome c is released from the mitochondria and binds to adapter proteins. This complex recruits and activates caspase-9, which then initiates the caspase cascade, ultimately leading to apoptosis.

How do proteins like BH3 and Bax contribute to the apoptotic process?

Proteins like BH3 and Bax are pro-apoptotic members of the Bcl-2 family. BH3 activates Bax, which promotes mitochondrial membrane permeabilization, leading to the release of cytochrome c and the initiation of the apoptotic signaling cascade. BH3 and other pro-apoptotic proteins are crucial in determining whether a cell undergoes apoptosis in response to stress signals.