Protein kinase C-zeta overexpression induces erythroid phenotype in the monocytic leukaemia cell line U937.
Previous studies have established that protein kinase C-zeta (PKC-zeta) is critical for neuronal cell differentiation. However, the role of PKC-zeta in haematopoietic cell differentiation is less clear. In this study, we have investigated the influence of PKC-zeta overexpression on the phenotype of the human monocytic U937 leukaemic cells. In two PKC-zeta-overexpressing clones (U937 zetaJ and U937 zetaB), PKC-zeta expression levels and activity were three to fourfold higher, and the enzyme accumulated both in the cytoplasm and in the nucleus compared with U937 control cells. PKC-zeta-overexpressing U937 cells exhibited an erythroid phenotype characterized by high levels of glycophorin A, cell haemoglobinization, increased GATA-1 transcripts and protein expression, compared with controls. Immunoprecipitation studies revealed that GATA-1 protein was constitutively phosphorylated in PKC-zeta-overexpressing cells. Moreover, GATA-1 did not interact with PKC-zeta but interacted with ERK1, which was constitutively activated and accumulated in the nucleus of U937 zetaJ. However, ERK1 phosphorylation inhibition by PD098059 did not influence either GATA-1 phosphorylation or GATA-1/ERK1 interaction. Collectively, these results suggest a model in which PKC-zeta induces MEK-dependent ERK1 activation, ERK1 translocation to the nucleus, GATA-1/ERK1 interaction and ERK1-independent GATA-1 phosphorylation resulting in GATA-1 accumulation. To conclude, this study provides evidence for the role of PKC-zeta in erythroid gene regulation.
Institut National de la Santé et de la Recherche Médicale (INSERM) E9910, Institut Claudius Régaud, 20 Rue du pont Saint-Pierre, 31052 Toulouse Cedex, France. demas.v@chu-toulouse.fr
Véronique
V
Mansat-De Mas
Aurélie
A
de Thonel
Vanessa
V
Gaulin
Cécile
C
Demur
Guy
G
Laurent
Anne
A
Quillet-Mary
D002454:Cell Differentiation; D004268:DNA-Binding Proteins / Q000378:metabolism; D015672:Erythroid Precursor Cells / Q000166:cytology* / Q000378:metabolism; D050981:Erythroid-Specific DNA-Binding Factors; D005434:Flow Cytometry; D050982:GATA1 Transcription Factor; D006801:Humans; D007938:Leukemia / Q000378:metabolism / Q000473:pathology*; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D010641:Phenotype; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism; D020298:U937 Cells
D004268:DNA-Binding Proteins; D050981:Erythroid-Specific DNA-Binding Factors; D050982:GATA1 Transcription Factor; C494688:GATA1 protein, human; D014157:Transcription Factors; D011493:Protein Kinase C; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases