Both ERK and JNK are required for enhancement of MD-2 gene expression during differentiation of HL-60 cells.
BACKGROUND
MD-2 is associated with the extracellular domain of TLR4 (Toll-like receptor 4) and augments TLR4-dependent LPS (lipopolysaccharide) responses in vitro. Our previous investigation found that PMA-induced HL-60 cell differentiation to macrophages is associated largely with TLR2 and CD14 and, to a much lesser extent, with TLR4.


RESULTS
We studied the MD-2 expression during differentiation of HL-60 cells induced by PMA. The results showed that PMA, but not VitD(3) (1alpha,25-dihydroxy-vitamin D(3)), strongly induces MD-2 gene expression by HL-60 cells in a time- and dose-dependent manner. Treatment with an MEK [MAPK (mitogen-activated protein kinase)/ERK (extracellular-signal-regulated kinase) kinase] inhibitor (PD98059) and a JNK (c-Jun N-terminal kinase) inhibitor (SP600125) suppresses PMA-induced MD-2 gene expression, whereas impairment of p38 function by treatment with the inhibitor SB203580 has no effect on MD-2 mRNA. In order to reveal the possible molecular mechanism for such a regulation of MD-2 gene expression, we cloned and analysed the putative MD-2 gene promoter. Transient transfection of different deletion mutants demonstrated that the region -185/-171 (5'-TCCTTTACAGGAAGT-3') of the MD-2 gene promoter is closely related to gene transcription in response to PMA. Additionally, the transcription factor Elk-1 has been found to bind this specific motif.


CONCLUSIONS
These results suggest that ERK and JNK pathways are involved in PMA-mediated MD-2 gene expression during HL-60 cell differentiation, and the activation of the MEK/possible ERK/Elk signal pathway is the mechanism responsible for PMA-induced MD-2 gene expression in differentiated HL-60 cells.
Li
Changlin
C
Laboratory of Molecular Cell Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 320 Yue Yang Road, Shanghai 200031, People's Republic of China.
Yu
Yongshen
Y
Wang
Yun
Y
Liu
Lei
L
Zhang
Min
M
Sugano
Sumio
S
Wang
Zhengguo
Z
Chang
Zongliang
Z
D002454:Cell Differentiation / Q000187:drug effects; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015870:Gene Expression / Q000187:drug effects; D018922:HL-60 Cells; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051218:Lymphocyte Antigen 96 / Q000235:genetics* / Q000378:metabolism; D011401:Promoter Regions, Genetic; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D015398:Signal Transduction; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014157:Transcription Factors / Q000378:metabolism; D050807:ets-Domain Protein Elk-1 / Q000378:metabolism
C494112:ELK1 protein, human; C495377:LY96 protein, human; D051218:Lymphocyte Antigen 96; D047428:Protein Kinase Inhibitors; D014157:Transcription Factors; D050807:ets-Domain Protein Elk-1; D048049:Extracellular Signal-Regulated MAP Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D013755:Tetradecanoylphorbol Acetate