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Cell signaling and pathogenesis — What do bacterial pathogens such as cholera (Vibrio cholerae) and anthrax (Bacillus anthracis) have in common regarding host cell communication?

Difficulty: Medium

Correct Answer: They disrupt normal intracellular signal transduction mechanisms

Explanation:


Introduction:
Many bacterial toxins subvert host signaling to favor pathogen survival or dissemination. This question examines the shared theme of how cholera and anthrax toxins perturb intracellular signaling cascades rather than simply removing receptors or ligands.


Given Data / Assumptions:

  • Cholera toxin modifies G-protein signaling, raising cAMP in epithelial cells.
  • Anthrax edema factor acts as an adenylate cyclase; lethal factor targets MAPK pathways.
  • Signal transduction refers to intracellular events after receptor engagement.


Concept / Approach:
Identify the common denominator: both pathogens change second-messenger pathways (cAMP) and kinase cascades, derailing normal responses. This is broader and more accurate than receptor destruction or total ligand loss.


Step-by-Step Solution:

1) Cholera toxin ADP-ribosylates Gαs → sustained adenylate cyclase activation → high cAMP.2) Anthrax edema factor is a calmodulin-dependent adenylate cyclase → elevated cAMP; lethal factor cleaves MAPKK → impaired MAPK signaling.3) Elevated cAMP and disrupted kinase signaling alter transporters and gene expression, producing disease phenotypes.


Verification / Alternative check:
Experimental toxin exposure shows characteristic rises in cAMP and pathway-specific phosphorylation changes, consistent with disturbed transduction rather than receptor loss.


Why Other Options Are Wrong:

a) Widespread receptor destruction is not the hallmark here.b) Cells still produce many signals; toxins hijack pathways downstream.c) Ligand chemical alteration is not the primary mechanism.e) Effects extend beyond ion channels, prominently involving second messengers and kinases.


Common Pitfalls:
Confusing receptor-level antagonism with post-receptor toxin effects; overlooking second messengers like cAMP.


Final Answer:
They disrupt normal intracellular signal transduction mechanisms.

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