Related Experiment Video

Updated: Aug 7, 2026

Examining BCL-2 Family Function with Large Unilamellar Vesicles
08:35

Examining BCL-2 Family Function with Large Unilamellar Vesicles

Published on: October 5, 2012

Bcl-2 family members do not inhibit apoptosis by binding the caspase activator Apaf-1

K Moriishi1, D C Huang, S Cory

  • 1The Walter and Eliza Hall Institute of Medical Research, Post Office, Royal Melbourne Hospital, Victoria 3050, Australia.

Proceedings of the National Academy of Sciences of the United States of America
|August 18, 1999
PubMed

Insights

Prosurvival Bcl-2 proteins do not directly bind Apaf-1 to prevent apoptosis. Instead, they indirectly regulate Apaf-1 activity, challenging previous models of caspase activation and cell death.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • The Bcl-2 protein family regulates apoptosis, a crucial cell death process.
  • Prosurvival Bcl-2 members are thought to inhibit apoptosis by binding adaptor proteins like Apaf-1, thus preventing caspase activation.

Purpose of the Study:

  • To investigate the in vivo interaction between prosurvival Bcl-2 family members and Apaf-1.
  • To determine if Bcl-2 proteins directly inhibit Apaf-1-mediated caspase-9 activation.

Main Methods:

  • Co-immunoprecipitation studies using both overexpressed and endogenous proteins.
  • Analysis of interactions between Apaf-1, procaspase-9, and various Bcl-2 family members under apoptotic stimuli.

Main Results:

  • Apaf-1 directly binds procaspase-9, independent of Bcl-2 family members.
  • No direct binding was observed between Apaf-1 and any of the six known mammalian prosurvival Bcl-2 homologs or their viral counterparts.
  • Apoptotic stimuli did not induce binding between Apaf-1 and Bcl-2 family members.

Conclusions:

  • Prosurvival Bcl-2 homologs do not appear to sequester Apaf-1 to prevent apoptosis.
  • The mechanism by which Bcl-2 proteins inhibit apoptosis likely involves indirect regulation of Apaf-1 activity.

More Related Videos

Lighting Up the Pathways to Caspase Activation Using Bimolecular Fluorescence Complementation08:47

Lighting Up the Pathways to Caspase Activation Using Bimolecular Fluorescence Complementation

Published on: March 5, 2018

Measuring Caspase Activity Using a Fluorometric Assay or Flow Cytometry05:29

Measuring Caspase Activity Using a Fluorometric Assay or Flow Cytometry

Published on: March 24, 2023

Related Concept Videos

Apoptosis01:30

Apoptosis

Apoptosis is a combination of two Greek words, 'apo' and 'ptosis,' meaning separation and falling off, respectively. Hippocrates used this word to describe gangrene, which was caused due to bandaging of fractured bones. Apoptosis was distinguished from necrosis in 1970 when John Kerr reported observations of morphological changes occurring during apoptosis. During one experiment, he observed that the disruption of blood supply to the liver tissue resulted in a size reduction of the tissue.
Caspases01:24

Caspases

Caspase, a family of cysteine proteases, serve as effectors in apoptosis. The ced3 gene in C.elegans was first identified to be involved in apoptosis. This gene encodes the ced-3 caspase that is similar to the interleukin-1-beta converting enzyme or ICE in mammals. In addition to apoptosis, caspases also function in the inflammatory response. Inflammatory caspases are essential in activating pro-inflammatory cytokines that recruit immune cells and block the replication of pathogens inside cells.
The Extrinsic Apoptotic Pathway01:17

The Extrinsic Apoptotic Pathway

The extrinsic apoptotic pathway is initiated when extracellular death-inducing signals, such as specific cytokines, activate the death receptors expressed on the cell surface. The immune cells involved in this pathway are natural killer cells (NK cells) and cytotoxic T-lymphocytes. NK cells are critical in innate immune response, while cytotoxic T-lymphocytes are associated with adaptive immune response. These cells recognize specific receptors expressed on the altered cells and activate...
The Intrinsic Apoptotic Pathway01:31

The Intrinsic Apoptotic Pathway

Internal cellular stress, such as cellular injury or hypoxia, triggers intrinsic apoptosis. The B-cell lymphoma 2 (Bcl-2) family of proteins are the primary regulators of the intrinsic apoptotic pathway. For example, during DNA damage, checkpoint proteins, such as Ataxia Telangiectasia Mutated (ATM protein) and Checkpoints Factor-2 (Chk2) proteins, are activated. These proteins phosphorylate p53 which further activates pro-apoptotic proteins, such as Bax, Bak, PUMA, and Noxa, and inhibits...
Phagocytosis of Apoptotic Cells01:17

Phagocytosis of Apoptotic Cells

Cells undergoing apoptosis form apoptotic bodies that must be removed immediately to prevent inflammation, autoimmune diseases, and necrosis. Phagocytosis is carried out by professional phagocytes such as macrophages or  immature dendritic cells. Non-professional phagocytes such as  epithelial cells and fibroblasts also take part in this process; however, they are not as effective as professional phagocytes. 
Normal cells contain receptors that prevent them from being recognized by phagocytes.
Cellular Injury V: Apoptosis and Autophagy01:22

Cellular Injury V: Apoptosis and Autophagy

Cells respond to damage and stress through highly coordinated processes that decide whether they survive or undergo controlled self-destruction. Two major pathways involved in this regulation are apoptosis, a type of programmed cell death, and autophagy, a survival mechanism that helps cells adapt to adverse conditions.ApoptosisApoptosis removes aged or injured cells to maintain tissue balance. During this process, the cell shrinks, chromatin condenses and fragments, and membrane-bound...