Résumé
To identify the molecular mechanisms involved in phagocytosis, we generated random insertion mutants ofDictyostelium discoideum and selected two mutants defective for phagocytosis. Both represented insertions in the same gene, namedPHG1. This gene encodes a polytopic membrane protein with an N-terminal lumenal domain and nine potential transmembrane segments. Homologous genes can be identified in many species; however, their function is yet to be elucidated. Disruption of PHG1 caused a selective defect in phagocytosis of latex beads and Escherichia coli, but not Klebsiella aerogenes bacteria. This defect in phagocytosis was caused by a decrease in the adhesion of mutant cells to phagocytosed particles. These results indicate that the Phg1 protein is involved in the adhesion of Dictyosteliumto various substrates, a crucial event of phagocytosis and demonstrate the usefulness of a genetic approach to dissect the molecular events involved in the phagocytic process.