Dataset Information
P38? MAPK upregulates atrogin1/MAFbx by specific phosphorylation of C/EBP?.
Ontology highlight
ABSTRACT: Unlabelled
Background
The p38 mitogen-activated protein kinases (MAPK) family plays pivotal roles in skeletal muscle metabolism. Recent evidence revealed that p38? and p38? exert paradoxical effects on muscle protein homeostasis. However, it is unknown why p38?, but not p38?, is capable of mediating muscle catabolism via selective activation of the C/EBP? that upregulates atrogin1/MAFbx.Methods
Tryptic phosphopeptide mapping was carried out to identify p38?- and p38?-mediated phosphorylation sites in C/EBP?. Chromosome immunoprecipitation (ChIP) assay was used to evaluate p38? and p38? effect on C/EBP? binding to the atrogin1/MAFbx promoter. Overexpression or siRNA-mediated gene knockdown of p38? and p38?, and site-directed mutagenesis or knockout of C/EBP?, were used to analyze the roles of these kinases in muscle catabolism in C2C12 myotubes and mice.Results
Cellular expression of constitutively active p38? or p38? resulted in phosphorylation of C/EBP? at multiple serine and threonine residues; however, only p38? phosphorylated Thr-188, which had been known to be critical to the DNA-binding activity of C/EBP?. Only p38?, but not p38?, activated C/EBP?-binding to the atrogin1/MAFbx promoter. A C/EBP? mutant in which Thr-188 was replaced by alanine acted as a dominant-negative inhibitor of atrogin1/MAFbx upregulation induced by either p38? or Lewis lung carcinoma (LLC) cell-conditioned medium (LCM). In addition, knockdown of p38? specifically inhibited C/EBP? activation and atrogin1/MAFbx upregulation induced by LCM. Finally, expression of active p38? in mouse tibialis anterior specifically induced C/EBP? phosphorylation at Thr-188, atrogin1/MAFbx upregulation and muscle mass loss, which were blocked in C/EBP?-null mice.Conclusions
The ? and ? isoforms of p38 MAPK are capable of recognizing distinct phosphorylation sites in a substrate. The unique capacity of p38? in mediating muscle catabolism is due to its capability in phosphorylating Thr-188 of C/EBP?.
SUBMITTER: Zhang G
PROVIDER: S-EPMC3534568 | biostudies-literature | 2012 Oct
REPOSITORIES: biostudies-literature
Publications
p38β MAPK upregulates atrogin1/MAFbx by specific phosphorylation of C/EBPβ.
Skeletal muscle 20121009 1
<h4>Unlabelled</h4><h4>Background</h4>The p38 mitogen-activated protein kinases (MAPK) family plays pivotal roles in skeletal muscle metabolism. Recent evidence revealed that p38α and p38β exert paradoxical effects on muscle protein homeostasis. However, it is unknown why p38β, but not p38α, is capable of mediating muscle catabolism via selective activation of the C/EBPβ that upregulates atrogin1/MAFbx.<h4>Methods</h4>Tryptic phosphopeptide mapping was carried out to identify p38α- and p38β-medi ...[more]
