page_title: Ced-9
section_title: Function
hierarchical_section_title: Ced-9 / Function
caption_attribution_description: English: Simplified apoptotic pathway of C. elegans
context_page_description: Cell death abnormality gene 9, also known as apoptosis regulator CED-9, is a gene found in Caenorhabditis elegans that inhibits/represses programmed cell death. The gene was discovered while searching for mutations in the apoptotic pathway after the discovery of the apoptosis promoting genes CED-3 and CED-4. The gene gives rise to the apoptosis regulator CED-9 protein found as an Integral membrane protein in the mitochondrial membrane. The protein is homologous to the human apoptotic regulator Bcl-2 as well as all other proteins in the Bcl-2 protein family. CED-9 is involved in the inhibition of CED-4 which is the activator of the CED-3 caspase. Because of the pathway homology with humans as well as the specific protein homology, CED-9 has been used to represent the human cell apoptosis interactions of Bcl-2 in research.
context_section_description: Cell death, or apoptosis during early development is crucial for the correct morphology and refractivity of adult C. elegans. This process involves a signal and interaction cascade of proteins leading to the engulfment and death of the targeted cell. Proteins in this cascade can be categorized into two groups; pro-apoptotic and anti-apoptotic. Pro-apoptotic proteins activate the apoptosis pathway while anti-apoptotic proteins suppress the pathway. CED-9 is classified as an anti-apoptotic protein.
  Apoptosis in C. elegans is often simplified to interactions between four major proteins in the pathway; EGL-1, CED-9, CED-4, and CED-3. CED-3 is the final protease in the interaction network and is responsible for activating the proteins involved in cell disassembly. CED-9 is said to protect cells from the apoptosis pathway. Under normal conditions, in a cell not experiencing apoptotic signalling, CED-9 forms a complex with CED-4 at the membrane of the mitochondria. This interaction sequesters the pro-apoptotic signalling of CED-4. CED-4 consists of an asymmetric dimer of CED-4a and CED-4b proteins in which CED-9 can specifically recognize and bind CED-4a. This interaction is a highly specific recognition and binding interaction between the N-terminal tails of both proteins. When the cell receives an apoptotic signal via a receptor commonly referred to as a "death receptor", the protein EGL-1 is activated. The active EGL-1 binds CED-9 causing a Conformational change that interrupts and inhibits the CED-9 - CED-4 interaction. CED-4 is free to dissociate and activate the CED-3 protease effectively triggering the final stages for apoptosis.
caption: Simplified outline of the apoptosis pathway observed in C. elegans.
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