title: Characterization of Rab21-positive tubular endosomes induced by PI3K inhibitors.
abstract: We found that wortmannin, a potent phosphoinositide 3-kinase (PI3K) inhibitor, markedly induced the formation of Rab21-positive tubular compartments in A431 cells. By time-lapse fluorescence microscopy of live cells co-expressing fluorescent protein-fused Rab21 and other marker proteins, it was shown that the Rab21-positive tubules in wortmannin-treated cells were derived from Rab5-positive early endosomes, but not from late endosomes, recycling endosomes, lysosomes or the trans-Golgi network. The formation of Rab21-positive tubules was very dynamic and required microtubules. Rab21-positive tubules were also formed by the treatment of cells with 3-methyladenine (3-MA), which inhibits class III PI3K rather than class I PI3K. Furthermore, the loss of PI(3)P correlated with the tubulation of Rab21-positive endosomes in cells co-expressing fluorescent protein-fused Rab21 and a tandem FYVE domain. These results suggest that the lowering of PI(3)P as a result of class III PI3K inhibition may be an important cue for the morphological change of Rab21-positive early endosomes from vesicular to tubular form.
authors.affiliation: Department of Histology and Cell Biology, School of Medicine, Kagawa University, Miki, Kagawa 761-0793, Japan.
authors.forename: Youhei
authors.initials: Y
authors.lastname: Egami
authors.forename: Nobukazu
authors.initials: N
authors.lastname: Araki
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives / Q000494:pharmacology; D000730:Androstadienes / Q000494:pharmacology*; D045744:Cell Line, Tumor; D011992:Endosomes / Q000737:chemistry* / Q000187:drug effects / Q000648:ultrastructure; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006801:Humans; D008856:Microscopy, Fluorescence; D008870:Microtubules / Q000502:physiology; D000081082:Phosphoinositide-3 Kinase Inhibitors; D000077191:Wortmannin; D020691:rab GTP-Binding Proteins / Q000032:analysis*
chemical_list: D000730:Androstadienes; D004791:Enzyme Inhibitors; D000081082:Phosphoinositide-3 Kinase Inhibitors; C025946:3-methyladenine; C415145:RAB21 protein, human; D020691:rab GTP-Binding Proteins; D000225:Adenine; D000077191:Wortmannin