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At the molecular level, hyperactive apoptosis can be caused by defects in signaling pathways that regulate the Bcl-2 family proteins. Increased expression of apoptotic proteins such as BIM, or their decreased proteolysis, leads to cell death and can cause a number of pathologies, depending on the cells where excessive activity of BIM occurs.
Bcl-2 was the first oncogene found to cause cancer-inhibiting apoptosis. It is over expressed in tumors and is resistant to chemotherapy. [18] Scientists have found that binding depressors to Bcl-2 anti-apoptotic proteins inhibits them and leaves direct activators free to interact with Bax and Bak. [18]
These pro-apoptotic proteins are in turn activated by BH3-only proteins, and are inhibited by the function of BCL-2 and its relative BCL-Xl. [11] There are additional non-canonical roles of BCL-2 that are being explored. BCL-2 is known to regulate mitochondrial dynamics, and is involved in the regulation of mitochondrial fusion and fission.
Apoptosis regulator BAX, also known as bcl-2-like protein 4, is a protein that in humans is encoded by the BAX gene. [5] BAX is a member of the Bcl-2 gene family.BCL2 family members form hetero- or homodimers and act as anti- or pro-apoptotic regulators that are involved in a wide variety of cellular activities.
The combinations of the domains in the proteins determine its role in the apoptosis process. Members of the family that inhibit apoptosis include Bcl-2 itself, Bcl-XL, and Bcl-w, which possess all four of the domains. [3] Bcl-2 is the most well known of the anti-apoptotic members, and is classified as an oncogene. Studies have shown that the ...
The p53 upregulated modulator of apoptosis (PUMA) also known as Bcl-2-binding component 3 (BBC3), is a pro-apoptotic protein, member of the Bcl-2 protein family. [5] [6] In humans, the Bcl-2-binding component 3 protein is encoded by the BBC3 gene. [5] [6] The expression of PUMA is regulated by the tumor suppressor p53.
Proteins downstream of all 3 UPR receptor pathways have been identified as having pro-apoptotic roles. However, the point at which the 'apoptotic switch' is activated has not yet been determined, but it is a logical consideration that this should be beyond a certain time period in which resolution of the stress has not been achieved.
There are another two proteins worth mentioning that inhibit the release of cytochrome c in the mitochondria. Bcl-2 and Bcl-xl are anti-apoptotic and therefore prevent cell death. There is a potential mutation that can occur in that causes the overactivity of Bcl-2. It is the translocation between chromosomes 14 and 18.