Changes in spatial and temporal localization of Dictyostelium homologues of TRAP1 and GRP94 revealed by immunoelectron microscopy.
TRAP1 (tumor necrosis factor receptor-associated protein 1) is a member of the molecular chaperone HSP90 (90-kDa heat shock protein) family. In this study, we mainly examined the behavior of Dictyostelium TRAP1 homologue, Dd-TRAP1, during Dictyostelium development by immunoelectron microscopy. In vegetatively growing D. discoideum Ax-2 cells, Dd-TRAP1 locates in nucleolus and vesicles in addition to the cell cortex including cell membrane. Many of Dd-TRAP1 molecules moved to the mitochondrial matrix in response to differentiation, although Dd-TRAP1 on the cell membrane seems to be retained. Some Dd-TRAP1 was also found to be secreted to locate outside the cell membrane in Ax-2 cells starved for 6 h. At the multicellular slug stage, Dd-TRAP1 was primarily located in mitochondria and cell membrane in both prestalk and prespore cells. More importantly, in differentiating prespore cells, a significant number of Dd-TRAP1 locates in the PSV (prespore-specific vacuole) that is a sole cell type-specific organelle and essential for spore wall formation, whereas some Dd-TRAP1 in the cell cortical region of prestalk cells. These findings strongly suggest the importance of Dd-TRAP1 regulated temporally and spatially during Dictyostelium development. Incidentally, we also have certified that the glucose-regulated protein 94 (Dd-GRP94) is predominantly located in Golgi vesicles and cisternae, followed by its colocalization with Dd-TRAP1 in the PSV.
Yamaguchi
Hitomi
H
Department of Developmental Biology and Neurosciences, Graduate School of Life Sciences, Tohoku University, Aoba, Sendai 980-8578, Japan.
Morita
Tsuyoshi
T
Amagai
Aiko
A
Maeda
Yasuo
Y
D000818:Animals; D004023:Dictyostelium / Q000235:genetics / Q000254:growth & development / Q000378:metabolism* / Q000648:ultrastructure*; D018507:Gene Expression Regulation, Developmental; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D018841:HSP90 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D016253:Microscopy, Immunoelectron; D008928:Mitochondria / Q000378:metabolism / Q000648:ultrastructure; D008954:Models, Biological; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D016053:RNA, Protozoan / Q000235:genetics / Q000378:metabolism; D014617:Vacuoles / Q000378:metabolism / Q000648:ultrastructure
D018840:HSP70 Heat-Shock Proteins; D018841:HSP90 Heat-Shock Proteins; D008565:Membrane Proteins; D015800:Protozoan Proteins; D012333:RNA, Messenger; D016053:RNA, Protozoan; C018551:glucose-regulated proteins