calcimycin and Leukemia--Megakaryoblastic--Acute

We investigated the intracellular processes of the shape change in the human megakaryoblastic leukemia cell, MEG-01, by platelet agonists. Thrombin induced the formation of many pseudopods. This shape change was also induced by TPA and 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 induced by thrombin. Shape change was inhibited by cytochalasin B. Protein kinase C (RKC) inhibitor, H-7, markedly inhibited thrombin-induced shape change, while the myosin light chain kinase (MLCK) inhibitor, 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 MLCK.

Topics: 1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; Actin Cytoskeleton; Calcimycin; Humans; Isoquinolines; Leukemia, Megakaryoblastic, Acute; Megakaryocytes; Microscopy, Electron; Piperazines; Protein Kinase C; Thrombin; Tissue Plasminogen Activator; Tumor Cells, Cultured