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Activation of Apoptosis by Cytoplasmic Microinjection of Cytochrome c
07:42

Activation of Apoptosis by Cytoplasmic Microinjection of Cytochrome c

Published on: June 29, 2011

Apoptosis induced by microinjection of cytochrome c is caspase-dependent and is inhibited by Bcl-2

O T Brustugun1, K E Fladmark, S O Doskeland

  • 1Department of Anatomy and Cell Biology, University of Bergen, Arstadveien 19, N-5009 Bergen, Norway.

Cell Death and Differentiation
|April 14, 1999
PubMed

Insights

Microinjection of cytochrome c triggers apoptosis across diverse cell types, characterized by specific cellular changes. The anti-apoptotic protein Bcl-2 also inhibits this process, suggesting broader roles in cell death regulation.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Apoptosis, or programmed cell death, is a fundamental biological process.
  • Cytochrome c's role in apoptosis has been primarily linked to mitochondrial release.
  • The direct effects of extramitochondrial cytochrome c on apoptosis are less understood.

Purpose of the Study:

  • To investigate the direct apoptotic effects of microinjected cytochrome c in various cell types.
  • To characterize the morphological and biochemical features of cytochrome c-induced apoptosis.
  • To determine the role of Bcl-2 in modulating apoptosis induced by extramitochondrial cytochrome c.

Main Methods:

  • Microinjection of cytochrome c into multiple cell lines (IPC-81, Swiss 3T3, Clone 8, NRK, H295, Y1, HEK 293).
  • Assessment of apoptotic phenotypes, including phosphatidylserine externalization and ultrastructural changes.
  • Inhibition studies using caspase inhibitor Z-VAD.fmk and transfection with Bcl-2.

Main Results:

  • Microinjected cytochrome c rapidly induced apoptosis in all tested cell types.
  • Apoptotic features included phosphatidylserine externalization, cell detachment, chromatin condensation, and cell shrinkage.
  • Bcl-2 transfection significantly reduced sensitivity to microinjected cytochrome c, and caspase inhibition prevented apoptosis.

Conclusions:

  • Extramitochondrial cytochrome c acts as a general inducer of apoptosis in cells with functional caspase systems.
  • Bcl-2 can inhibit apoptosis not only by regulating cytochrome c release but also by interfering with cytoplasmic caspase activation.
  • These findings highlight a dual role for Bcl-2 in apoptosis regulation, impacting both mitochondrial and cytoplasmic events.

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