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Analysis of HIV Protease Killing Through Caspase 8 Reveals a Novel Interaction Between Caspase 8 and Mitochondria.

Algeciras-Schimnich A, Belzacq-Casagrande AS, Bren GD, Nie Z, Taylor JA, Rizza SA, Brenner C, Badley AD - Open Virol J (2007)

Bottom Line: Since casp8p41 does not contain the catalytic cysteine at position 360, the mechanism by which casp8p41 initiates apoptosis is unclear.Moreover, death induced by casp8p41 requires the presence of mitochondria, and in intact cells, casp8p41 colocalizes with mitochondria.These results illuminate a novel mechanism of cell death induced by a caspase 8 cleavage fragment whereby mitochondrial interaction leads to depolarization and cytochrome c release.

View Article: PubMed Central - PubMed

Affiliation: Division of Infectious Diseases, Mayo Clinic, Rochester, MN 55905, USA.

ABSTRACT
Human Immunodeficiency Virus (HIV) protease initiates apoptosis of HIV-infected cells by proteolytic cleavage of procaspase 8, creating a novel peptide termed casp8p41. Expression of casp8p41 alone is sufficient to initiate caspase-dependent cell death associated with mitochondrial depolarization. Since casp8p41 does not contain the catalytic cysteine at position 360, the mechanism by which casp8p41 initiates apoptosis is unclear. We demonstrate that casp8p41 directly causes mitochondrial depolarization and release of cytochrome c with downstream caspase 9 activation. Moreover, death induced by casp8p41 requires the presence of mitochondria, and in intact cells, casp8p41 colocalizes with mitochondria. These results illuminate a novel mechanism of cell death induced by a caspase 8 cleavage fragment whereby mitochondrial interaction leads to depolarization and cytochrome c release.

No MeSH data available.


Related in: MedlinePlus

Casp8p41 colocalizes with mitochondria. (A) HeLa cells were transfected with GFP, GFP-casp8p41, or GFP-casp8FL. After 6 hours of transfection, cells were stained with MitoTracker® red, and nuclei was counterstained with DAPI. Staining was visualized by confocal microscopy. The figure shows the overlay of the staining: GPF constructs (green), Mitotracker (red), and DAPI (blue). (B) Same as in A. Images of GFP-casp8p41 transfected HeLa cells are shown individually for each staining and as an overlay.
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Figure 4: Casp8p41 colocalizes with mitochondria. (A) HeLa cells were transfected with GFP, GFP-casp8p41, or GFP-casp8FL. After 6 hours of transfection, cells were stained with MitoTracker® red, and nuclei was counterstained with DAPI. Staining was visualized by confocal microscopy. The figure shows the overlay of the staining: GPF constructs (green), Mitotracker (red), and DAPI (blue). (B) Same as in A. Images of GFP-casp8p41 transfected HeLa cells are shown individually for each staining and as an overlay.

Mentions: Having demonstrated that casp8p41 acts directly upon mitochondria in vitro, resulting in mitochondrial depolarization and cytochrome c release, we next assessed the relevance of these events in intact cells. HeLa cells were transfected with GFP alone, GFP full-length procaspase 8, or GFP casp8p41 and stained for mitochondria (red) and nuclear morphology (blue) (Fig. 4A). GFP control and GFP full-length procaspase 8 transfected cells exhibited diffuse GFP staining with no mitochondrial colocalization. In contrast, GFP casp8p41 transfected cells exhibited punctuate staining (Fig. 4A) that upon greater magnification colocalized with mitochondria (Fig. 4B).


Analysis of HIV Protease Killing Through Caspase 8 Reveals a Novel Interaction Between Caspase 8 and Mitochondria.

Algeciras-Schimnich A, Belzacq-Casagrande AS, Bren GD, Nie Z, Taylor JA, Rizza SA, Brenner C, Badley AD - Open Virol J (2007)

Casp8p41 colocalizes with mitochondria. (A) HeLa cells were transfected with GFP, GFP-casp8p41, or GFP-casp8FL. After 6 hours of transfection, cells were stained with MitoTracker® red, and nuclei was counterstained with DAPI. Staining was visualized by confocal microscopy. The figure shows the overlay of the staining: GPF constructs (green), Mitotracker (red), and DAPI (blue). (B) Same as in A. Images of GFP-casp8p41 transfected HeLa cells are shown individually for each staining and as an overlay.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC2548302&req=5

Figure 4: Casp8p41 colocalizes with mitochondria. (A) HeLa cells were transfected with GFP, GFP-casp8p41, or GFP-casp8FL. After 6 hours of transfection, cells were stained with MitoTracker® red, and nuclei was counterstained with DAPI. Staining was visualized by confocal microscopy. The figure shows the overlay of the staining: GPF constructs (green), Mitotracker (red), and DAPI (blue). (B) Same as in A. Images of GFP-casp8p41 transfected HeLa cells are shown individually for each staining and as an overlay.
Mentions: Having demonstrated that casp8p41 acts directly upon mitochondria in vitro, resulting in mitochondrial depolarization and cytochrome c release, we next assessed the relevance of these events in intact cells. HeLa cells were transfected with GFP alone, GFP full-length procaspase 8, or GFP casp8p41 and stained for mitochondria (red) and nuclear morphology (blue) (Fig. 4A). GFP control and GFP full-length procaspase 8 transfected cells exhibited diffuse GFP staining with no mitochondrial colocalization. In contrast, GFP casp8p41 transfected cells exhibited punctuate staining (Fig. 4A) that upon greater magnification colocalized with mitochondria (Fig. 4B).

Bottom Line: Since casp8p41 does not contain the catalytic cysteine at position 360, the mechanism by which casp8p41 initiates apoptosis is unclear.Moreover, death induced by casp8p41 requires the presence of mitochondria, and in intact cells, casp8p41 colocalizes with mitochondria.These results illuminate a novel mechanism of cell death induced by a caspase 8 cleavage fragment whereby mitochondrial interaction leads to depolarization and cytochrome c release.

View Article: PubMed Central - PubMed

Affiliation: Division of Infectious Diseases, Mayo Clinic, Rochester, MN 55905, USA.

ABSTRACT
Human Immunodeficiency Virus (HIV) protease initiates apoptosis of HIV-infected cells by proteolytic cleavage of procaspase 8, creating a novel peptide termed casp8p41. Expression of casp8p41 alone is sufficient to initiate caspase-dependent cell death associated with mitochondrial depolarization. Since casp8p41 does not contain the catalytic cysteine at position 360, the mechanism by which casp8p41 initiates apoptosis is unclear. We demonstrate that casp8p41 directly causes mitochondrial depolarization and release of cytochrome c with downstream caspase 9 activation. Moreover, death induced by casp8p41 requires the presence of mitochondria, and in intact cells, casp8p41 colocalizes with mitochondria. These results illuminate a novel mechanism of cell death induced by a caspase 8 cleavage fragment whereby mitochondrial interaction leads to depolarization and cytochrome c release.

No MeSH data available.


Related in: MedlinePlus