Evidence for the role of G-proteins in flow stimulation of dinoflagellate bioluminescence.
Luminescent dinoflagellates respond to flow by the production of light. The primary mechanotransduction event is unknown, although downstream events include a calcium flux in the cytoplasm, a self-propagating action potential across the vacuole membrane, and a proton flux into the cytoplasm that activates the luminescent chemistry. Given the role of GTP-binding (G) proteins in the mechanotransduction of flow by nonmarine cells and the presence of G-proteins in dinoflagellates, it was hypothesized that flow-stimulated dinoflagellate bioluminescence involves mechanotransduction by G-proteins. In the present study, osmotic swelling of cells of the dinoflagellate Lingulodinium polyedrum was used as a drug delivery system to introduce GDPbetaS, an inhibitor of G-protein activation. Osmotically swollen cells produced higher levels of flow-stimulated bioluminescence at a lower threshold of shear stress, indicating they were more flow sensitive. GDPbetaS inhibited flow-stimulated bioluminescence in osmotically swollen cells and in cells that were restored to the isosmotic condition following hypoosmotic treatment with GDPbetaS. These results provide evidence that G-proteins are involved in the mechanotransduction of flow in dinoflagellates and suggest that G-protein involvement in mechanotransduction may be a fundamental evolutionary adaptation.
Chen
Antony K
AK
La Jolla Bioengineering Institute, La Jolla, CA 92037, USA.
Latz
Michael I
MI
Sobolewski
Peter
P
Frangos
John A
JA
D000818:Animals; D004141:Dinoflagellida / Q000187:drug effects / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006153:Guanosine Diphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D049449:Luminescence; D008163:Luminescent Measurements; D009994:Osmolar Concentration; D012623:Seawater / Q000737:chemistry; D013873:Thionucleotides / Q000494:pharmacology
D013873:Thionucleotides; D006153:Guanosine Diphosphate; C023427:guanosine 5'-O-(2-thiodiphosphate); D019204:GTP-Binding Proteins