Phg1p Is a Nine-transmembrane Protein Superfamily Member Involved in Dictyostelium Adhesion and Phagocytosis

doi:10.1074/jbc.M006725200

Phg1p Is a Nine-transmembrane Protein Superfamily Member Involved in Dictyostelium Adhesion and Phagocytosis*

From the ^‡Département de Morphologie, Centre Médical Universitaire, Université de Genève, 1 rue Michel Servet, CH-1211 Genève 4, Switzerland, the ^¶Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California 94305, the ^**Institut de Biologie et de Chimie des Protéines, UPR 412, CNRS, 69367 Lyon, France, and the ^‡Laboratoire de Biochimie et Biophysique des Systèmes Intégrés, UMR 314, CNRS, Commissariat à l'Energie Atomique, 38054 Grenoble, France

Abstract

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.

Footnotes

↵* This work was supported in part by a START fellowship of the Fonds National Suisse de la Recherche Scientifique and a grant from the Fondation Gabriella Giorgi-Cavaglieri (both to P. C.); by grants from the Association pour la Recherche contre le Cancer (to F. L. and S. C.) and the Fondation pour la Recherche Médicale (to F. L.); by a joint grant for “Adhesion Cellules-materiau” from CNRS/INSERM (to F. B.); and by Japan Society for the Promotion of Science Grant RFTF96L00105 and Ministry of Education, Science, Sports and Culture of Japan Grant 08283107, both for theDictyostelium cDNA project in Japan.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵§ These authors contributed equally to this work.
↵‖ A Schering-Plough Research Institute fellow of the Life Sciences Research Foundation.
↵§§ To whom correspondence should be addressed. Tel.: 41-22-702-5293; Fax: 41-22-702-5338; E-mail: pierre.cosson@medecine.unige.ch.
Published, JBC Papers in Press, August 15, 2000, DOI 10.1074/jbc.M006725200
↵2 E. Décavé, F. Brückert, Y. Bréchet, B. Fourcade, and M. Satre, manuscript in preparation.
Abbreviations:

PBS

phosphate-buffered saline

FACS

fluorescence-activated cell sorter

FITC

fluorescein isothiocyanate

Pa

pascal(s)
- Received July 27, 2000.
- Revision received August 10, 2000.
The American Society for Biochemistry and Molecular Biology, Inc.