Inhibition of SAPK2a/p38 prevents hnRNP A0 phosphorylation by MAPKAP-K2 and its interaction with cytokine mRNAs.
Lipopolysaccharide (LPS) stimulates production of inflammatory mediators, partly by stabilizing [interleukin-6 (IL-6), cyclooxygenase 2 (COX-2)] and/or stimulating translation [tumour necrosis factor-alpha (TNF-alpha)] of their mRNAs. Such regulation depends on AU-rich elements (AREs) within the 3'-untranslated regions and is partially suppressed by SB 203580 (which inhibits SAPK2a/p38). The LPS-induced production of TNF-alpha and IL-6 is suppressed in MAPKAP-K2-deficient mice (a kinase activated by SAPK2a/p38). Here, we identify 18 macrophage proteins that bind to AREs and show that hnRNP A0 is a major substrate for MAPKAP-K2 in this fraction. MAPKAP-K2 phosphorylated hnRNP A0 at Ser84 in vitro and this residue became phosphorylated in LPS-stimulated cells. Phosphorylation was prevented by SB 203580 and suppressed in macrophages derived from MAPKAP-K2-deficient mice. The mRNAs encoding TNF-alpha, COX-2 and macrophage inflammatory protein-2 (MIP-2) bound to hnRNP A0 in LPS-stimulated macrophages, an interaction prevented by SB 203580. The LPS-induced stabilization of MIP-2 mRNA and production of MIP-2 protein were abolished when macrophages were incubated with SB 203580 plus PD 184352 (which inhibits the classical MAP kinase cascade). Our data suggest that LPS-induced binding of hnRNP A0 to AREs may contribute to the post-transcriptional regulation of specific mRNAs.
Rousseau
Simon
S
MRC Protein Phosphorylation Unit, School of Life Sciences, University of Dundee, MSI/WTB complex, Dow Street, Dundee DD1 5EH, UK. e-mail: s.rousseau@dundee.ac.uk
Morrice
Nick
N
Peggie
Mark
M
Campbell
David G
DG
Gaestel
Matthias
M
Cohen
Philip
P
D000818:Animals; D054426:Chemokine CXCL2; D004791:Enzyme Inhibitors / Q000494:pharmacology; D034441:Heterogeneous-Nuclear Ribonucleoproteins / Q000378:metabolism*; D007093:Imidazoles / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D015846:Monokines / Q000235:genetics; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011725:Pyridines / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics; D048051:p38 Mitogen-Activated Protein Kinases; D000099190:MAP-Kinase-Activated Kinase 2
D054426:Chemokine CXCL2; D004791:Enzyme Inhibitors; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D007093:Imidazoles; D047908:Intracellular Signaling Peptides and Proteins; D020928:Mitogen-Activated Protein Kinases; D015846:Monokines; D017346:Protein Serine-Threonine Kinases; D011725:Pyridines; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D048051:p38 Mitogen-Activated Protein Kinases; D000099190:MAP-Kinase-Activated Kinase 2; C093642:SB 203580