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Action of Pasteurella multocida toxin depends on the helical domain of Galphaq

Joachim H C Orth1, Simona Lang, Klaus Aktories

  • 1Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Albert-Ludwigs Universität Freiburg, Albertstrasse 25, D-79104 Freiburg, Germany.

The Journal of Biological Chemistry
|June 12, 2004
PubMed

Insights

Pasteurella multocida toxin (PMT) specifically activates Gαq, not Gα11. A key peptide region in Gαq

Area of Science:

  • Molecular Biology
  • Cellular Signaling
  • Microbial Pathogenesis

Background:

  • Pasteurella multocida toxin (PMT) is a 146-kDa protein that activates cellular signal transduction pathways.
  • PMT induces activation of phospholipase Cβ, RhoA, Jun kinase, and extracellular signal-regulated kinase.
  • Previous studies indicated PMT-induced effects are mediated by Gαq but not Gα11.

Purpose of the Study:

  • To investigate the molecular basis for PMT's specific activation of Gαq over Gα11.
  • To identify the specific regions within Gαq responsible for PMT interaction and activation.

Main Methods:

  • Utilized Gαq-deficient cells reconstituted with retroviral vectors encoding Gαq or Gα11.
  • Constructed and analyzed Gαq/Gα11 chimeras to pinpoint critical amino acid residues.
  • Assessed PMT-induced phospholipase Cβ activation in cells expressing wild-type and chimeric Gα proteins.

Main Results:

  • Reconstitution of PMT-induced phospholipase Cβ activation was observed only with Gαq, not Gα11.
  • A specific peptide region (residues 105-113) of Gαq was identified as essential for PMT activity.
  • Mutating specific residues (Q105, N109) in Gα11 to mimic Gαq residues restored PMT responsiveness.

Conclusions:

  • The all-helical domain of Gαq is crucial for PMT's specific action.
  • This domain plays an essential functional role in G(q) protein-mediated signal transduction.
  • PMT's unique specificity relies on distinct structural features within the Gαq protein.

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