title: Novel redistribution of the Ca(2+)-dependent cell adhesion molecule DdCAD-1 during development of Dictyostelium discoideum.
abstract: Dictyostelium discoideum cells express DdCAD-1, a Ca(2+)-dependent cell-cell adhesion molecule, soon after the initiation of development. DdCAD-1 is a soluble protein which shares a significant degree of sequence similarity with E-cadherin. Laser scanning confocal microscopy of the subcellular localization of DdCAD-1 has revealed a nonrandom pattern of DdCAD-1 distribution. DdCAD-1 is present mostly as diffusely stained material in the cytoplasm during the initial stage of development. However, a drastic redistribution takes place before the onset of cell aggregation, when DdCAD-1 become localized predominantly at the cell periphery and an enrichment of DdCAD-1 occurs on membrane ruffles. A high concentration of DdCAD-1 also becomes associated with lamellipodia and filopodia, which often appear to participate in cell contact formation. Although DdCAD-1 is present in high concentrations in contact regions during early development, it disappears rapidly from these areas during cell aggregation. This redistribution is accompanied by an accumulation of the Ca(2+)-independent cell adhesion molecule gp80 in contact regions. During chemotactic migration, DdCAD-1 is present primarily on cells at the tip and on the outer margin of cell streams. In contrast, gp80 is concentrated in contact regions among cells within well-developed streams. This dynamic redistribution suggests a unique role for DdCAD-1 in the recruitment of cells into streams and in the formation of initial contacts, but it may not be required to maintain stable contacts in the presence of gp80.
authors.affiliation: Banting and Best Department of Medical Research, University of Toronto, Ontario, Canada.
authors.forename: H
authors.initials: H
authors.lastname: Sesaki
authors.forename: C H
authors.initials: CH
authors.lastname: Siu
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000032:analysis / Q000096:biosynthesis*; D015815:Cell Adhesion Molecules / Q000032:analysis / Q000096:biosynthesis* / Q000378:metabolism; D002449:Cell Aggregation; D002450:Cell Communication / Q000502:physiology; D002465:Cell Movement / Q000502:physiology; D004023:Dictyostelium / Q000166:cytology / Q000254:growth & development* / Q000378:metabolism; D015850:Interleukin-6 / Q000032:analysis / Q000378:metabolism; D008565:Membrane Proteins / Q000502:physiology; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D008858:Microscopy, Phase-Contrast; D011554:Pseudopodia / Q000378:metabolism / Q000648:ultrastructure; D013499:Surface Properties
chemical_list: D002135:Calcium-Binding Proteins; D015815:Cell Adhesion Molecules; C100604:DdCAD-1 protein, Dictyostelium discoideum; D015850:Interleukin-6; D008565:Membrane Proteins; D002118:Calcium