Cyclic AMP Regulates Social Behavior in African Trypanosomes

Area of Science:

• Parasitology
• Cellular signaling
• Microbial social behavior

Background:

• Protozoan parasites like Trypanosoma brucei display complex social behaviors, including coordinated group movement (social motility).
• The molecular mechanisms underlying T. brucei social motility and its reliance on extracellular signals remain largely uncharacterized.
• Social behavior in bacteria is well-studied, but parallels in protozoan parasites are less understood.

Purpose of the Study:

• To elucidate the signaling pathways governing social motility in Trypanosoma brucei.
• To investigate the role of cyclic AMP (cAMP) signaling within the parasite's flagellum.
• To explore potential transcomplementation phenomena in T. brucei social behavior.

Main Methods:

• Pharmacological inhibition of cAMP-specific phosphodiesterase (PDE).
• Fluorescence resonance energy transfer (FRET)-based sensors to monitor intracellular cAMP dynamics.
• RNA interference (RNAi) to knockdown the flagellar PDEB1 gene.
• Co-culture experiments with fluorescently tagged wild-type and mutant parasites.

Main Results:

• Inhibition of PDE activity completely abolished T. brucei social motility without affecting individual cell viability or motility.
• Increased intracellular cAMP levels correlated with the loss of social motility.
• RNAi-mediated knockdown of PDEB1 phenocopied the effects of pharmacological PDE inhibition.
• PDEB1 knockdown cells exhibited social motility defects that were rescued in the presence of wild-type cells (transcomplementation).

Conclusions:

• T. brucei social motility is critically dependent on flagellar cAMP signaling pathways.
• The flagellar enzyme PDEB1 plays a crucial role in regulating cAMP levels and coordinating social behavior.
• This study demonstrates transcomplementation in parasitic protozoa, revealing intercellular communication in mixed communities.