Related Experiment Videos
Pertussis and cholera toxin ADP-ribosylation in Dictyostelium discoideum membranes
L Khachatrian1, C Klein, A Howlett
1Department of Pharmacology, St. Louis University School of Medicine, St. Louis, MO 63104.
Abstract:
We report a 39 kDa substrate for cholera and pertussis toxins is present in D. discoideum membranes. This protein did not co-migrate with alpha subunits of either Gs (45 kDa and 52 kDa) or Gi (41 kDa) from control mammalian cells. The presence of GTP or its non-hydrolyzable analogs enhanced the ADP-ribosylation in response to cholera toxin, but did not significantly alter ADP-ribosylation by pertussis toxin. Divalent cations inhibited the ADP-ribosylation by both toxins. The possible association of this novel G-protein with D. discoideum adenylate cyclase may underlie some of the unique regulatory features of this enzyme. Alternatively, this G-protein may regulate one of several other cellular responses mediated by the cAMP receptor.
Insights
Researchers identified a novel 39 kDa G-protein in Dictyostelium discoideum membranes. This protein is a substrate for cholera and pertussis toxins, suggesting a role in cellular signaling pathways.
Area of Science:
- Cell Biology
- Biochemistry
- Molecular Biology
Background:
- Dictyostelium discoideum (D. discoideum) is a model organism for studying cellular processes.
- G proteins are key regulators of cellular signaling pathways.
- Cholera toxin and pertussis toxin are bacterial toxins that ADP-ribosylate specific G proteins, altering their function.
Purpose of the Study:
- To identify and characterize novel G proteins in D. discoideum membranes.
- To investigate the substrate specificity and regulation of ADP-ribosylation by cholera and pertussis toxins in D. discoideum.
- To explore the potential role of a novel G protein in D. discoideum signaling.
Main Methods:
- Membrane preparation from D. discoideum.
- ADP-ribosylation assays using cholera toxin and pertussis toxin.
- Co-migration analysis with known G protein subunits (Gs and Gi) from mammalian cells.
- Investigation of the effects of GTP analogs and divalent cations on ADP-ribosylation.
Main Results:
- A 39 kDa protein substrate for both cholera and pertussis toxins was identified in D. discoideum membranes.
- This 39 kDa protein did not co-migrate with alpha subunits of mammalian Gs or Gi proteins.
- GTP analogs enhanced cholera toxin-mediated ADP-ribosylation but had minimal effect on pertussis toxin-mediated ADP-ribosylation.
- Divalent cations inhibited ADP-ribosylation by both toxins.
Conclusions:
- A novel G protein, distinct from mammalian Gs and Gi, exists in D. discoideum membranes.
- This novel G protein is a substrate for cholera and pertussis toxins, indicating its involvement in cellular signaling.
- The unique regulatory properties suggest potential association with D. discoideum adenylate cyclase or regulation of cAMP receptor-mediated responses.