Model for capping derived from inhibition of surface receptor capping by free fatty acids.

When low concentrations (2-5 mole %) of cis unsaturated free fatty acids (group A) are intercalated into lymphocyte plasma membrane, capping is inhibited. No effect is seen with trans unsaturated or saturated fatty acids (group B). The capping inhibition is reversible with increasing doses of extracellular calcium. Fluorescence photobleaching recovery has shown that the group A free fatty acids do not inhibit the receptor immobilization associated with patch formation, but inhibit the final energy-dependent movement of the patched receptors into a cap. We have also shown that the group A free fatty acids cause a shift in membrane-bound calcium to the lipid phase from probable protein-associated sites. We have incorporated these findings into a model for capping and membrane-cytoskeletal interactions.