Drainin required for membrane fusion of the contractile vacuole in Dictyostelium is the prototype of a protein family also represented in man.
The contractile vacuole expels water by forming a channel with the plasma membrane and thus enables cells to survive in a hypo-osmotic environment. Here we characterize drainin, a Dictyostelium protein involved in this process, as the first member of a protein family represented in fission yeast, Caenorhabditis elegans and man. Gene replacement in Dictyostelium shows that drainin acts at a checkpoint of channel formation between the contractile vacuole and the plasma membrane. A green fluorescent protein fusion of drainin localizes specifically to the contractile vacuole and rescues its periodic discharge in drainin-null cells. Drainin is a peripheral membrane protein, requiring a short hydrophobic stretch in its C-terminal region for localization and function. We suggest that drainin acts in a signaling cascade that couples a volume-sensing device in the vacuolar membrane to the membrane fusion machinery.
Becker
M
M
Max-Planck-Institut für Biochemie, D-82152 Martinsried, Germany.
Matzner
M
M
Gerisch
G
G
D000595:Amino Acid Sequence; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism / Q000648:ultrastructure; D002470:Cell Survival; D003001:Cloning, Molecular; D004023:Dictyostelium / Q000166:cytology* / Q000254:growth & development / Q000378:metabolism; D004705:Endocytosis; D011992:Endosomes / Q000378:metabolism; D017353:Gene Deletion; D005816:Genetic Complementation Test; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism / Q000648:ultrastructure; D008561:Membrane Fusion; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D009997:Osmotic Pressure; D010641:Phenotype; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014617:Vacuoles / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D014867:Water / Q000378:metabolism
D008565:Membrane Proteins; D015800:Protozoan Proteins; D011993:Recombinant Fusion Proteins; C120615:drainin; D014867:Water