The involvement of the rho gene product, a small molecular weight GTP-binding protein, in polyploidization of a human megakaryocytic cell line, CMK.
The role of rho proteins, which are ras p21-related small GTP-binding proteins, in megakaryocyte endomitosis was examined using a botulinum C3 exoenzyme (C3), a rho inactivating enzyme. The megakaryocytic leukemia cell line CMK expressed high levels of rhoA and rhoC mRNAs, whereas rhoB mRNA was expressed at a very low level. The addition of C3 to the culture medium caused ADP-ribosylation of the rho proteins in CMK cells in a dose- and time-dependent manner. This procedure also induced a higher frequency of polyploid cells with increased glycoprotein (GP) IIb/IIIa antigens on the cells. This effect of C3 on both ploidy and the antigen expression was abolished by prior incubation of C3 with an anti-C3 monoclonal antibody. Cytochalasin B, an actin polymerization inhibitor, also induced polyploid cells; however, it did not stimulate the expression of GP IIb/IIIa antigens in CMK cells. This finding suggests that C3-induced increase in the expression of GP IIb/IIIa antigens was not through the actin microfilament disassembly. The present study suggests that the rho p21 is a partly regulatory component in polyploidization and GP IIb/IIIa antigen expression of a human megakaryocytic cell line, CMK.
Takada
M
M
Department of Laboratory Medicine, Kobe University School of Medicine, Japan.
Morii
N
N
Kumagai
S
S
Ryo
R
R
D036002:ADP Ribose Transferases / Q000494:pharmacology; D000246:Adenosine Diphosphate Ribose / Q000378:metabolism; D001905:Botulinum Toxins; D002454:Cell Differentiation / Q000187:drug effects; D004273:DNA, Neoplasm / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000502:physiology*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D015850:Interleukin-6 / Q000494:pharmacology; D007947:Leukemia, Megakaryoblastic, Acute; D008533:Megakaryocytes / Q000473:pathology*; D010980:Platelet Membrane Glycoproteins / Q000378:metabolism; D011123:Polyploidy; D012333:RNA, Messenger / Q000235:genetics; D012334:RNA, Neoplasm / Q000235:genetics; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D020741:rho GTP-Binding Proteins
D004273:DNA, Neoplasm; D015850:Interleukin-6; D010980:Platelet Membrane Glycoproteins; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D000246:Adenosine Diphosphate Ribose; D036002:ADP Ribose Transferases; C063007:exoenzyme C3, Clostridium botulinum; D001905:Botulinum Toxins; D019204:GTP-Binding Proteins; D020741:rho GTP-Binding Proteins; D013755:Tetradecanoylphorbol Acetate