Cellular Homeostasis and Energy Production

The ubiquitin system is a cellular pathway responsible for tagging and degrading proteins that are damaged, misfolded, or no longer needed.

The ubiquitin system plays a crucial role in maintaining protein homeostasis, ensuring that damaged or unnecessary proteins are removed.

The ubiquitin system is essential for the controlled progression of the cell cycle by targeting key regulatory proteins for degradation.

Specific proteins involved in DNA repair are tagged with ubiquitin, allowing for the recruitment of repair machinery to the damaged site.

Ubiquitination helps regulate the duration and intensity of signaling pathways by controlling the stability of key signaling proteins.

The ubiquitination process involves three main enzymes: E1 (ubiquitin-activating enzyme), E2 (ubiquitin-conjugating enzyme), and E3 (ubiquitin ligase).

E3 ligases confer specificity to the ubiquitination process by recognizing and binding to specific target proteins.

Once tagged with ubiquitin, proteins are transported to the 26S proteasome, a large protein complex that breaks down the tagged proteins into their constituent peptides.

Granzyme B is a serine protease that cleaves after aspartic acid residues and activates caspase-mediated apoptosis.

Granzyme B directly activates caspase 3, which can trigger apoptosis.

Granzyme B disrupts the mitochondrial transmembrane potential, leading to the release of pro-apoptotic factors like cytochrome C.

Granzyme B cleaves BID, which then disrupts the outer mitochondrial membrane, releasing cytochrome C and triggering apoptosis.

Granzyme B cleaves ICAD/DFF45, which leads to DNA fragmentation.

Cells that overexpress natural inhibitors of caspases, like BCL2, CRMA, and SPI2, are still susceptible to Granzyme B-mediated apoptosis.

Granzyme B can directly activate caspase 8, as well as caspases 3, 6, and 7, involved in the caspase-dependent pathway.

A family of serine proteases found within the cytotoxic granules of cytotoxic T lymphocytes (CTLs) and natural killer (NK) cells.

The most abundant granzyme that induces cell death via a caspase-independent mechanism.

A protein that forms pores in target cell membranes, allowing granzymes to enter the cytosol.

A type of cell death characterized by DNA fragmentation, membrane blebbing, and nuclear fragmentation.

A complex of proteins found in the endoplasmic reticulum, involved in transcription and DNA repair.

A protein that causes single-stranded DNA nicking, a distinct form of DNA damage.

A process where cells release cytotoxic granules containing perforin and granzymes to kill target cells.

Cells that recognize and destroy infected or cancerous cells.

The specialized interface between a CTL or NK cell and its target cell.

Reactive oxygen species (ROS) are molecules that can damage cells. They are often elevated during oxidative stress.

A large protein complex responsible for recognizing and degrading damaged or misfolded proteins in cells.

A process where cells break down their internal components to recycle nutrients and survive harsh conditions.

A process where cells release toxic substances and 'burst' open, often causing inflammation, and is usually triggered by damage or injury.

A cellular signaling pathway that uses ubiquitin proteins to tag and mark proteins for degradation by the proteasome.

A cellular signaling pathway that uses SUMO proteins to modify and change the functions of other proteins.

A state of balance within a cell, where all its functions are working together in harmony to maintain optimal health.

A group of enzymes responsible for breaking down proteins into smaller peptides and amino acids.

The process of cells breaking down and recycling their own components, a key aspect of autophagy.

A protein that plays a critical role in necrosis, triggering cell lysis and inflammation.

Apoptosis is a programmed cell death process that involves a series of biochemical events to eliminate unwanted or damaged cells in a controlled manner.

The intrinsic pathway is triggered from inside the cell by stress signals like DNA damage, leading to the release of pro-apoptotic proteins from mitochondria.

The extrinsic pathway is activated by signals from outside the cell, such as the binding of death receptors by molecules like TNF.

Caspases are a family of proteases (enzymes that break down proteins) that play a central role in executing apoptosis.

Cytotoxic T Lymphocytes (CTLs) are immune cells that recognize and destroy cells displaying foreign antigens like viral proteins or cancer cell markers.

CTLs induce apoptosis in target cells through the release of cytotoxic proteins like perforin and granzyme.

Perforin creates pores in the target cell's membrane, allowing granzyme to enter and activate the caspase cascade, leading to apoptosis.

Apoptosis prevents the spread of infections by eliminating infected cells, removing damaged cells to maintain tissue integrity, and eliminating cancer cells to control tumor growth.

Disruptions to apoptosis, leading to either too much or too little, can contribute to various diseases like cancer, neurodegenerative disorders, and immune system dysfunction.

Autophagy is a cellular process that involves the breakdown and recycling of cellular components within lysosomes.