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Detection of mitochondrial localization of p53
1Department of Pathology, State University of New York at Stony Brook, USA.
Abstract:
p53 is a master regulator of cell death pathways and has transcription-dependent and transcription- independent modes of action. Mitochondria are major signal transducers in apoptosis and are critical for p53-dependent cell death. Recently, we discovered that a fraction of stress-induced wild-type p53 protein rapidly translocates to mitochondria during p53-dependent apoptosis. Suborganellar localization by various methods shows that p53 predominantly localizes to the surface of mitochondria. Moreover, bypassing the nucleus by targeting p53 to mitochondria is sufficient to induce apoptosis in p53-null cells, without requiring further DNA damage. Here, we describe subcellular fractionation as a classic technique for detecting mitochondrial p53 in cell extracts. It consists of cell homogenization by hypo-osmotic swelling, removal of nuclear components by low-speed centrifugation, and mitochondrial isolation by a discontinuous sucrose density gradient. p53 and other mitochondrial proteins can then be detected by standard immunoblotting procedures. The quality of mitochondrial isolates can be verified for purity and intactness.
Insights
Wild-type p53 protein rapidly moves to mitochondria during apoptosis. Targeting p53 directly to mitochondria can trigger cell death, even without nuclear involvement.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- The p53 protein is a key regulator of cell death pathways, acting through both transcription-dependent and independent mechanisms.
- Mitochondria play a crucial role in apoptosis, acting as signal transducers for p53-mediated cell death.
Purpose of the Study:
- To investigate the suborganellar localization of p53 during apoptosis.
- To explore the role of mitochondrial p53 in inducing apoptosis.
- To describe a method for detecting p53 in mitochondrial fractions.
Main Methods:
- Subcellular fractionation involving cell homogenization, nuclear component removal, and sucrose density gradient centrifugation.
- Detection of p53 and mitochondrial proteins using immunoblotting.
- Verification of mitochondrial isolate purity and integrity.
Main Results:
- Stress-induced wild-type p53 rapidly translocates to mitochondria during apoptosis.
- p53 predominantly localizes to the surface of mitochondria.
- Targeting p53 directly to mitochondria is sufficient to induce apoptosis in p53-null cells.
Conclusions:
- p53's localization to mitochondria is a critical event in apoptosis.
- Mitochondrial p53 can directly induce apoptosis, independent of nuclear activity.
- Subcellular fractionation is a reliable method for studying mitochondrial p53.