A cytohesin homolog in Dictyostelium amoebae.
BACKGROUND
Dictyostelium, an amoeboid motile cell, harbors several paralogous Sec7 genes that encode members of three distinct subfamilies of the Sec7 superfamily of Guanine nucleotide exchange factors. Among them are proteins of the GBF/BIG family present in all eukaryotes. The third subfamily represented with three members in D. discoideum is the cytohesin family that has been thought to be metazoan specific. Cytohesins are characterized by a Sec7 PH tandem domain and have roles in cell adhesion and migration.


RESULTS
Dictyostelium SecG exhibits highest homologies to the cytohesins. It harbors at its amino terminus several ankyrin repeats that are followed by the Sec7 PH tandem domain. Mutants lacking SecG show reduced cell-substratum adhesion whereas cell-cell adhesion that is important for development is not affected. Accordingly, multicellular development proceeds normally in the mutant. During chemotaxis secG(-) cells elongate and migrate in a directed fashion towards cAMP, however speed is moderately reduced.


CONCLUSIONS
The data indicate that SecG is a relevant factor for cell-substrate adhesion and reveal the basic function of a cytohesin in a lower eukaryote.
Shina
Maria Christina
MC
Center for Biochemistry, Medical Faculty, University of Cologne, Köln, Germany.
Müller
Rolf
R
Blau-Wasser
Rosemarie
R
Glöckner
Gernot
G
Schleicher
Michael
M
Eichinger
Ludwig
L
Noegel
Angelika A
AA
Kolanus
Waldemar
W
D000595:Amino Acid Sequence; D000656:Amoeba / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D000818:Animals; D015815:Cell Adhesion Molecules / Q000235:genetics* / Q000378:metabolism; D002633:Chemotaxis / Q000502:physiology; D000242:Cyclic AMP / Q000378:metabolism; D004023:Dictyostelium / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D018503:Genome, Protozoan / Q000235:genetics; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000145:classification / Q000235:genetics / Q000378:metabolism; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D009068:Movement / Q000502:physiology; D009154:Mutation; D010802:Phylogeny; D020033:Protein Isoforms / Q000145:classification / Q000235:genetics / Q000378:metabolism; D015800:Protozoan Proteins / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
D015815:Cell Adhesion Molecules; D020662:Guanine Nucleotide Exchange Factors; D020033:Protein Isoforms; D015800:Protozoan Proteins; D049452:Green Fluorescent Proteins; D000242:Cyclic AMP