Unsaturated free fatty acids regulate cAMP relay and cell-cell adhesion duringDictyostelium discoideum aggregation

Abstract

Cell-cell adhesion and cAMP-stimulated cAMP production (cAMP relay) regulate the aggregation that occurs early in theDictyostelium discoideum developmental cycle. Increasing the concentration of neutral lipids inD. discoideum membranes inhibits both cell-cell adhesion and cAMP relay. Fractionation experiments revealed that it was the free fatty acids, one group of the neutral lipids, that inhibited both cAMP relay and cell-cell adhesion. Work with commercially-available free fatty acids demonstrated that the addition of saturated free fatty acids, palmitic acid and stearic acid, did not alter cell-cell adhesion or cAMP relay. The addition of unsaturated free fatty acids inhibited both cAMP relay and cell-cell adhesion in a dose-dependent, saturable manner. To test the physiological significance of these observations, the concentrations of endogenous unsaturated fatty acids were modified by altering theD. discoideum diet. Decreasing the amount of fatty acids 18 carbons long with 2 double bonds enhanced cAMP relay and cell-cell adhesion. These results suggest that fatty acids may be important regulators of cAMP responsiveness and cell-cell adhesion duringD. discoideum aggregation, and therefore may play important roles in development.