title: Small guanosine triphosphatase Rho/Rho-associated kinase as a novel regulator of intracellular redistribution of lysosomes in invasive tumor cells.
abstract: To investigate the role of RhoA on the intracellular membrane dynamics of lysosomes in rat hepatoma cells (MM1), we analyzed the localization of lysosomal aspartic proteinase cathepsin D by confocal immunofluorescence microscopy in the dominant active RhoA-transfected cells. Here we show that the transfection of the dominant active form of human small guanosine triphosphatase (GTPase) RhoA in MMI cells, a highly invasive cell line, causes the redistribution and spreading of small punctate structures stained for cathepsin D throughout the cytoplasm. We found that the microtubule organization was markedly different in the two cell lines: uniformly developed and polymerized microtubule filaments were seen in the mock transfectants; however, the dynamic organization of microtubules was less pronounced in the active RhoA transfectants. Furthermore, we found for the first time that a selective inhibitor of Rho-associated kinase (p160ROCK), Y-27632, impeded the subcellular spreading of cathepsin D staining and promoted reclustering of cathepsin D toward the perinuclear region in the active RhoA-transfected cells. To our knowledge, this is the first indication that the RhoA/ROCK-mediated signaling pathway is involved in the intracellular membrane dynamics of lysosomes by regulating the cytoskeletal microtubule organization as well as the actin cytoskeletons.
authors.affiliation: Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan. nishimur@bioc.phar.kyushu-u.ac.jp
authors.forename: Y
authors.initials: Y
authors.lastname: Nishimura
authors.forename: K
authors.initials: K
authors.lastname: Itoh
authors.forename: K
authors.initials: K
authors.lastname: Yoshioka
authors.forename: M
authors.initials: M
authors.lastname: Uehata
authors.forename: M
authors.initials: M
authors.lastname: Himeno
mesh_terms: D000199:Actins / Q000378:metabolism; D000577:Amides / Q000494:pharmacology; D000818:Animals; D006528:Carcinoma, Hepatocellular; D002402:Cathepsin D / Q000378:metabolism; D002451:Cell Compartmentation / Q000502:physiology; D011992:Endosomes / Q000201:enzymology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005455:Fluorescent Antibody Technique; D006801:Humans; D008113:Liver Neoplasms; D008247:Lysosomes / Q000201:enzymology*; D008870:Microtubules / Q000201:enzymology; D016296:Mutagenesis / Q000502:physiology; D021381:Protein Transport / Q000502:physiology; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D015398:Signal Transduction / Q000502:physiology; D014162:Transfection; D014407:Tumor Cells, Cultured / Q000166:cytology / Q000201:enzymology; D020742:rhoA GTP-Binding Protein / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*
chemical_list: D000199:Actins; D000577:Amides; D004791:Enzyme Inhibitors; D011725:Pyridines; C108830:Y 27632; D002402:Cathepsin D; D020742:rhoA GTP-Binding Protein