title: Thrombin-induced shape change in human megakaryoblastic leukemic cells, MEG-01, is mediated by protein kinase C.
abstract: We investigated the intracellular processes of the shape change in human megakaryoblastic leukemic cells, MEG-01, by platelet agonists. Thrombin induced the formation of many pseudopods. This shape change was also induced by phorbol 12-myristate 13 acetate (TPA) and weakly by Ca2+ ionophore, A23187, but not by ADP, collagen, or epinephrine. Electron microscopy and FITC-labeled phalloidin staining revealed thick submembranous microfilament bundles in the pseudopods of the shape-changed cells by thrombin. Shape change was inhibited by cytochalasin B. Since Ca(2+)-dependent phosphorylation reactions play central role on the initiation of shape change of platelet, we examined the effects of protein kinase C (PKC) inhibitor, H-7, and myosin light chain (MLC) kinase inhibitor, ML-9, on the shape change of MEG-01 cells induced by thrombin, and observed that H-7 potently inhibited thrombin-induced shape change, while ML-9 did not. These results suggest that thrombin-induced reorganization of microfilaments and shape change of MEG-01 cells are mediated by PKC, but not by MLC kinase.
authors.affiliation: First Department of Internal Medicine, Nagoya University School of Medicine, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Goto
authors.forename: M
authors.initials: M
authors.lastname: Kobayashi
authors.forename: T
authors.initials: T
authors.lastname: Murate
authors.forename: T
authors.initials: T
authors.lastname: Hotta
authors.forename: M
authors.initials: M
authors.lastname: Hagiwara
authors.forename: T
authors.initials: T
authors.lastname: Hoshino
authors.forename: H
authors.initials: H
authors.lastname: Hidaka
authors.forename: H
authors.initials: H
authors.lastname: Saito
mesh_terms: D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D000199:Actins / Q000032:analysis; D001381:Azepines / Q000494:pharmacology; D000001:Calcimycin / Q000494:pharmacology; D048429:Cell Size / Q000187:drug effects*; D003571:Cytochalasin B / Q000494:pharmacology; D006801:Humans; D007546:Isoquinolines / Q000494:pharmacology; D008533:Megakaryocytes; D010703:Phorbol Esters / Q000494:pharmacology; D010879:Piperazines / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013917:Thrombin / Q000494:pharmacology*; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure
chemical_list: D000199:Actins; D001381:Azepines; D007546:Isoquinolines; D010703:Phorbol Esters; D010879:Piperazines; C056218:ML 9; D000001:Calcimycin; D003571:Cytochalasin B; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D011493:Protein Kinase C; D013917:Thrombin