Document Detail

Okadaic acid overcomes the blocked cell cycle caused by depleting Cdc2-related kinases in Trypanosoma brucei.
MedLine Citation:
PMID:  16949574     Owner:  NLM     Status:  MEDLINE    
Mitosis and cytokinesis are highly coordinated in eukaryotic cells. But procyclic-form Trypanosoma brucei under G1 or mitotic arrest is still capable of dividing, resulting in anucleate daughter cells (zoids). Okadaic acid (OKA), an inhibitor of protein phosphatases PP1 and PP2A, is known to inhibit kinetoplast replication and cell division yielding multinucleate cells with single kinetoplasts. However, when OKA was applied to cells arrested in G1 or G2/M phase via RNAi knockdown of specific cdc2-related kinases (CRKs), DNA synthesis and nuclear division were resumed without kinetoplast replication or cell division, resulting in multinucleate cells as in the wild type. Cells arrested in G2/M via depleting the mitotic cyclin CycB2 or an aurora B kinase homologue TbAUK1 were, however, not released by OKA treatment. The phenomenon is thus similar to the OKA activation of Cdc2 in Xenopus oocyte by inhibiting PP2A [Maton, et al., Differential regulation of Cdc2 and Aurora-A in Xenopus oocytes: a crucial role of phosphatase 2A. J. Cell Sci. 118 (2005) 2485-2494]. A simultaneous knockdown of the seven PP1s or the PP2A catalytic subunit in T. brucei by RNA interference did not, however, result in multinucleate cells. This could be explained by assuming a negative regulation, either directly or indirectly, of CRK by an OKA-sensitive phosphatase, which could be a PP2A as in the Xenopus oocyte and a positive regulation of kinetoplast replication by an OKA-susceptible protein(s). Test of a PP2A-specific inhibitor, fostriecin, on cells arrested in G2/M via CRK depletion or a knockdown of the PP2A catalytic subunit from the CRK-depleted cells both showed a partial lift of the G2/M block without forming multinucleate cells. These observations support the abovementioned assumption and suggest the presence of a novel OKA-sensitive protein(s) regulating kinetoplast replication that still remains to be identified.
Ziyin Li; Xiaoming Tu; Ching C Wang
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural     Date:  2006-08-02
Journal Detail:
Title:  Experimental cell research     Volume:  312     ISSN:  0014-4827     ISO Abbreviation:  Exp. Cell Res.     Publication Date:  2006 Nov 
Date Detail:
Created Date:  2006-10-09     Completed Date:  2007-01-09     Revised Date:  2012-08-01    
Medline Journal Info:
Nlm Unique ID:  0373226     Medline TA:  Exp Cell Res     Country:  United States    
Other Details:
Languages:  eng     Pagination:  3504-16     Citation Subset:  IM    
Department of Pharmaceutical Chemistry, University of California, San Francisco, CA 94143-2280, USA.
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MeSH Terms
Alkenes / pharmacology
CDC2 Protein Kinase / genetics,  metabolism*
Cell Cycle / drug effects*,  physiology
Enzyme Inhibitors / pharmacology*
Isoenzymes / antagonists & inhibitors,  genetics,  metabolism
Okadaic Acid / pharmacology*
Phosphoprotein Phosphatases / antagonists & inhibitors,  genetics,  metabolism
Protein Phosphatase 2
Protein Subunits / genetics,  metabolism
Protozoan Proteins / genetics,  metabolism*
Pyrones / pharmacology
RNA Interference
Trypanosoma brucei brucei / cytology,  drug effects*,  physiology
Grant Support
Reg. No./Substance:
0/Alkenes; 0/Enzyme Inhibitors; 0/Isoenzymes; 0/Polyenes; 0/Protein Subunits; 0/Protozoan Proteins; 0/Pyrones; 78111-17-8/Okadaic Acid; 87810-56-8/fostriecin; EC Protein Kinase; EC protein,Trypanosoma brucei; EC protein, Trypanosoma brucei; EC Phosphatases; EC Phosphatase 2

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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