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The insecticidal toxin Makes caterpillars floppy (Mcf) promotes apoptosis in mammalian cells

A J Dowling1, P J Daborn, N R Waterfield

  • 1Department of Biology and Biochemistry, University of Bath, Bath BA2 7AY, UK.

Cellular Microbiology
|March 11, 2004
PubMed

Insights

The insecticidal toxin Makes caterpillars floppy (Mcf) induces apoptosis in mammalian cells, characterized by nuclear changes and caspase activation. This toxin

Area of Science:

  • Microbiology
  • Molecular Biology
  • Toxicology

Background:

  • Photorhabdus bacteria utilize toxins to eliminate insect hosts.
  • Makes caterpillars floppy (Mcf) toxin from Photorhabdus is sufficient for Escherichia coli to kill caterpillars.
  • Mcf toxin induces insect midgut epithelium shedding and haemocyte blebbing, suggesting apoptosis induction.

Purpose of the Study:

  • To investigate the hypothesis that Mcf toxin triggers apoptosis.
  • To examine the effects of E. coli-expressed Mcf on mammalian cell lines.
  • To determine if Mcf toxin induces apoptosis in non-insect cells.

Main Methods:

  • Mammalian cell lines (COS-7, NIH 3T3, HeLa) were treated with E. coli-expressed Mcf.
  • Apoptotic markers including nuclear morphology, caspase-3 activity, DNA laddering, and cleaved PARP were assessed.
  • Apoptosis inhibitor zVAD-fmk was used to confirm Mcf's role in apoptosis.
  • Transfection with truncated Mcf constructs was performed.

Main Results:

  • Mcf-treated cells exhibited apoptotic nuclear morphology, active caspase-3, and DNA laddering within 6 hours.
  • Cleaved PARP was detected after 16 hours, confirming apoptosis.
  • The apoptosis inhibitor zVAD-fmk prevented Mcf-induced cell death.
  • Expression of a truncated Mcf protein also induced cell destruction and localized to the Golgi apparatus.

Conclusions:

  • The insecticidal toxin Mcf induces apoptosis in mammalian cells.
  • Mcf toxin triggers key events of apoptosis, including caspase activation and DNA fragmentation.
  • While Mcf induces apoptosis, the specific intracellular pathway remains to be elucidated.

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