Ndm, a coiled-coil domain protein that suppresses macropinocytosis and has effects on cell migration

摘要

The ampA gene has a role in cell migration in Dictyostelium discoideum . Cells overexpressing AmpA show an increase in cell migration, forming large plaques on bacterial lawns. A second-site suppressor of this ampA- overexpressing phenotype identified a previously uncharacterized gene, ndm , which is described here. The Ndm protein is predicted to contain a coiled-coil BAR-like domain—a domain involved in endocytosis and membrane bending. ndm -knockout and Ndm-monomeric red fluorescent protein–expressing cell lines were used to establish a role for ndm in suppressing endocytosis. An increase in the rate of endocytosis and in the number of endosomes was detected in ndm? cells. During migration ndm? cells formed numerous endocytic cups instead of the broad lamellipodia structure characteristic of moving cells. A second lamellipodia-based function—cell spreading—was also defective in the ndm? cells. The increase in endocytosis and the defect in lamellipodia formation were associated with reduced chemotaxis in ndm? cells. Immunofluorescence results and glutathione S -transferase pull-down assays revealed an association of Ndm with coronin and F-actin. The results establish ndm as a gene important in regulating the balance between formation of endocytic cups and lamellipodia structures.