Dictyostelium discoideum lipids modulate cell-cell cohesion and cyclic AMP signaling.
During Dictyostelium discoideum development, cell-cell communication is mediated through cyclic AMP (cAMP)-induced cAMP synthesis and secretion (cAMP signaling) and cell-cell contact. Cell-cell contact elicits cAMP secretion and modulates the magnitude of a subsequent cAMP signaling response (D. R. Fontana and P. L. Price, Differentiation 41:184-192, 1989), demonstrating that cell-cell contact and cAMP signaling are not independent events. To identify components involved in the contact-mediated modulation of cAMP signaling, amoebal membranes were added to aggregation-competent amoebae in suspension. The membranes from aggregation-competent amoebae inhibited cAMP signaling at all concentrations tested, while the membranes from vegetative amoebae exhibited a concentration-dependent enhancement or inhibition of cAMP signaling. Membrane lipids inhibited cAMP signaling at all concentrations tested. The lipids abolished cAMP signaling by blocking cAMP-induced adenylyl cyclase activation. The membrane lipids also inhibited amoeba-amoeba cohesion at concentrations comparable to those which inhibited cAMP signaling. The phospholipids and neutral lipids decreased cohesion and inhibited the cAMP signaling response. The glycolipid/sulfolipid fraction enhanced cohesion and cAMP signaling. Caffeine, a known inhibitor of cAMP-induced adenylyl cyclase activation, inhibited amoeba-amoeba cohesion. These studies demonstrate that endogenous lipids are capable of modulating amoeba-amoeba cohesion and cAMP-induced activation of the adenylyl cyclase. These results suggest that cohesion may modulate cAMP-induced adenylyl cyclase activation. Because the complete elimination of cohesion is accompanied by the complete elimination of cAMP signaling, these results further suggest that cohesion may be necessary for cAMP-induced adenylyl cyclase activation in D. discoideum.
Fontana
D R
DR
Department of Microbiology, University of Minnesota, Minneapolis 55455.
Luo
C S
CS
Phillips
J C
JC
D000262:Adenylyl Cyclases / Q000378:metabolism; D002110:Caffeine / Q000494:pharmacology; D002449:Cell Aggregation; D002450:Cell Communication; D002454:Cell Differentiation; D002462:Cell Membrane / Q000502:physiology; D000242:Cyclic AMP / Q000502:physiology*; D006152:Cyclic GMP / Q000502:physiology; D004023:Dictyostelium / Q000166:cytology*; D004789:Enzyme Activation; D008563:Membrane Lipids / Q000502:physiology*
D008563:Membrane Lipids; D002110:Caffeine; D000242:Cyclic AMP; D000262:Adenylyl Cyclases; D006152:Cyclic GMP