Enhanced exocytosis of the receptor BT-R(1) induced by the Cry1Ab toxin of Bacillus thuringiensis directly correlates to the execution of cell death

Comp Biochem Physiol B Biochem Mol Biol. 2008 Apr;149(4):581-8. doi: 10.1016/j.cbpb.2007.12.006. Epub 2007 Dec 23.

Abstract

Cry1Ab toxin produced by Bacillus thuringiensis exerts insecticidal action upon binding to BT-R(1), a cadherin receptor localized in the midgut epithelium of the tobacco hornworm Manduca sexta. The univalent binding of toxin to receptor transmits a death signal into the cell and turns on a multi-step signal transduction pathway involving adenylyl cyclase (AC) and protein kinase A (PKA), which drives the biochemical events that culminate in oncotic cell death. Here, we report that cell killing by the Cry1Ab toxin is a dynamic episode in which the toxin promotes exocytotic transport of BT-R(1) from intracellular membrane vesicles to the plasma membrane. The resultant dramatic increase in BT-R(1) displayed on the surface of toxin-treated cells effects the recruitment and concomitant binding of additional toxin monomers which, in turn, amplifies the original signal in a cascade-like manner. Blocking the activation of AC/PKA signal transduction by either EDTA or PKAi inhibits exocytotic trafficking of BT-R(1) and prevents cell death. Moreover, the exocytosis inhibitor Exo1 blocks translocation of receptor and progression of cell death alike. Obviously, movement of BT-R(1) is mediated by toxin-induced signal transduction and amplification of this signaling apparently is critical to the execution of cell death.

MeSH terms

  • Animals
  • Bacillus thuringiensis / metabolism*
  • Bacillus thuringiensis Toxins
  • Bacterial Proteins / metabolism
  • Bacterial Proteins / toxicity*
  • Bacterial Toxins / metabolism
  • Bacterial Toxins / toxicity*
  • Cadherins / metabolism*
  • Cell Adhesion / drug effects
  • Cell Death / drug effects
  • Cell Line
  • Cell Membrane / metabolism
  • Cytotoxins / metabolism
  • Cytotoxins / toxicity
  • Endocytosis / drug effects
  • Endotoxins / metabolism
  • Endotoxins / toxicity*
  • Exocytosis / drug effects*
  • Gene Expression Regulation / drug effects
  • Hemolysin Proteins / metabolism
  • Hemolysin Proteins / toxicity*
  • Intracellular Space / metabolism
  • Manduca / cytology*
  • Manduca / drug effects*
  • Manduca / metabolism
  • Molecular Sequence Data
  • Receptors, Cell Surface / genetics
  • Receptors, Cell Surface / metabolism*
  • Signal Transduction / drug effects

Substances

  • Bacillus thuringiensis Toxins
  • Bacterial Proteins
  • Bacterial Toxins
  • Cadherins
  • Cytotoxins
  • Endotoxins
  • Hemolysin Proteins
  • Receptors, Cell Surface
  • insecticidal crystal protein, Bacillus Thuringiensis

Associated data

  • GENBANK/AF319973