Related Experiment Video
Updated: Aug 16, 2026
08:47
Lighting Up the Pathways to Caspase Activation Using Bimolecular Fluorescence Complementation
Published on: March 5, 2018
S-Nitrosylation of mitochondrial caspases
J B Mannick1, C Schonhoff, N Papeta
1Department of Medicine, University of Massachusetts Medical School, Shrewsbury, MA 01545, USA. joan.mannick@umassmed.edu
The Journal of Cell Biology
|September 12, 2001
Summary
Mitochondrial caspase-3 and caspase-9 zymogens are primarily S-nitrosylated, inhibiting their activity. This modification is reversed during apoptosis, suggesting S-nitrosylation regulates mitochondrial apoptotic pathways based on protein location.
Area of Science:
- Biochemistry
- Cell Biology
- Molecular Biology
Background:
- Caspase-3 is a key effector protease in apoptosis.
- S-nitrosylation of caspase-3 zymogen inhibits its activity in resting cells.
- Denitrosylation activates caspases during Fas-induced apoptosis.
Purpose of the Study:
- To identify the specific caspase subpopulations regulated by S-nitrosylation.
- To investigate the role of S-nitrosylation in mitochondrial caspase regulation.
Main Methods:
- Subcellular fractionation to isolate mitochondrial and cytoplasmic caspase-3.
- Analysis of S-nitrosylation status in different cellular compartments.
- Assessment of caspase-9 S-nitrosylation.
Main Results:
- The majority of mitochondrial caspase-3 zymogens, unlike cytoplasmic ones, are S-nitrosylated.
- Most mitochondrial caspase-9 also exhibits S-nitrosylation.
- Subcellular localization dictates the S-nitrosylation state of caspases.
Conclusions:
- S-nitrosylation is a critical regulatory mechanism for mitochondrial caspase function.
- Protein localization influences the inhibitory S-nitrosylation of caspases.
- This regulation is crucial for controlling apoptotic pathways originating from mitochondria.
Related Concept Videos
01:45Mitochondrial Membranes
A single mitochondrion is a bean-shaped organelle enclosed by a double-membrane system. The outer membrane of mitochondria is smooth and contains many porins - the integral membrane transporters. Porins enable free diffusion of ions and small uncharged molecules through the outer mitochondrial membrane but limit the transport of molecules larger than 5000 Daltons. Further, the outer mitochondrial membrane forms a unique structure called membrane contact sites with other subcellular organelles,...
01:46Electron Transport Chain: Complex I and II
The mitochondrial electron transport chain (ETC) is the main energy generation system in the eukaryotic cells. However, mitochondria also produce cytotoxic reactive oxygen species (ROS) due to the large electron flow during oxidative phosphorylation. While Complex I is one of the primary sources of superoxide radicals, ROS production by Complex II is uncommon and may only be observed in cancer cells with mutated complexes.
ROS generation is regulated and maintained at moderate levels necessary...
ROS generation is regulated and maintained at moderate levels necessary...
01:48ATP Synthase: Mechanism
In animals, the mitochondrial F1F0 ATP synthase is the key protein that synthesizes ATP molecules through a complex catalytic mechanism. While the nuclear genome encodes the majority of ATP synthase subunits, the mitochondrial genome encodes some of the enzyme's most critical components. The formation of this multi-subunit enzyme is a complex multi-step process regulated at the level of transcription, translation, and assembly. Defects in one or more of these steps can result in decreased ATP...
01:19Translocation of Proteins into the Mitochondria
Mitochondrial precursors are translocated to the internal subcompartments via independent mechanisms involving distinct protein machineries called translocases.
Sorting of outer membrane proteins:
Mitochondrial outer membrane proteins are of two types: the transmembrane, beta-barrel porins, and the membrane-anchored, alpha-helical proteins. Beta-barrel porin precursors are translocated by the TOM complex and inserted into the outer mitochondrial membrane by the SAM complex. In contrast,...
Sorting of outer membrane proteins:
Mitochondrial outer membrane proteins are of two types: the transmembrane, beta-barrel porins, and the membrane-anchored, alpha-helical proteins. Beta-barrel porin precursors are translocated by the TOM complex and inserted into the outer mitochondrial membrane by the SAM complex. In contrast,...
01:24Caspases
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.
01:31The 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...