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SARS-CoV nucleocapsid protein induced apoptosis of COS-1 mediated by the mitochondrial pathway

Lu Zhang1, Lai Wei, Dong Jiang

  • 1Hepatology Institute, Peking University, People's Hospital, Beijing, People's Republic of China.

Artificial Cells, Blood Substitutes, and Immobilization Biotechnology
|April 25, 2007
PubMed

Insights

The SARS coronavirus nucleocapsid protein triggers apoptosis in COS-1 cells via the mitochondrial pathway, involving reactive oxygen species and caspase activation. Other SARS proteins did not induce apoptosis in tested cell lines.

Area of Science:

  • Virology
  • Cell Biology
  • Molecular Biology

Background:

  • The SARS coronavirus nucleocapsid (N) protein's role in inducing apoptosis is not fully understood.
  • Investigating the specific mechanisms and pathways of SARS-CoV-induced cell death is crucial for understanding viral pathogenesis.

Purpose of the Study:

  • To determine if SARS coronavirus N, M, and S proteins induce apoptosis in cultured cell lines.
  • To elucidate the specific apoptotic pathway activated by the SARS-CoV N protein.

Main Methods:

  • Transfection of COS-1, Huh-7, and HepG2 cells with SARS-CoV N, M, and S genes.
  • Apoptosis assessment using Annexin V staining and electron microscopy.
  • Measurement of intracellular reactive oxygen species (ROS) and mitochondrial membrane potential (ΔPsim) via flow cytometry.
  • Western blot analysis for Cytochrome C, cleaved caspase-3, caspase-9, and PARP.

Main Results:

  • SARS-CoV N protein induced apoptosis in COS-1 cells under serum starvation.
  • Observed loss of ΔPsim, increased ROS, and Cytochrome C release.
  • Activation of caspase-3, caspase-9, and PARP cleavage was confirmed.
  • The pan-caspase inhibitor z-VAD-fmk blocked these apoptotic events.
  • SARS-CoV M and S proteins, and N protein in HepG2/Huh-7 cells, did not induce apoptosis under the tested conditions.

Conclusions:

  • SARS coronavirus N protein induces apoptosis in COS-1 cells through the intrinsic mitochondrial pathway.
  • The N protein's apoptotic effect is cell-type specific and mediated by ROS generation and mitochondrial dysfunction.

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