Insulin-activated Erk-mitogen-activated protein kinases phosphorylate sterol regulatory element-binding Protein-2 at serine residues 432 and 455 in vivo.
The transcription factor sterol regulatory element binding protein (SREBP)-2 plays a pivotal role in lipid metabolism. Previously, we have shown that the mature form of SREBP-2 is a substrate of Erk-mitogen-activated protein kinases (MAPK). The aim of the present study was to identify Erk-specific phosphorylation sites. Using a protein chemistry approach, we could identify Ser-432 and Ser-455 as major phosphorylation sites. Further characterization by electrophoretic mobility shift assay and promoter reporter gene analyses revealed that phosphorylation does not influence protein/DNA interaction, but enhances trans-activity. In intact cells, SREBP-2 is phosphorylated by insulin, which seems to be related to their bio-responses on low density lipoprotein receptor activity. These results suggest that activation of Erk-MAPK pathways by hormones such as insulin might be related to a novel regulatory principle of SREBP-2.
German Diabetes Center at the Heinrich-Heine University Düsseldorf, Institute for Clinical Biochemistry and Pathobiochemistry, D-40225 Düsseldorf, Germany.
Jorg
J
Kotzka
Stefan
S
Lehr
Gunther
G
Roth
Haluk
H
Avci
Birgit
B
Knebel
Dirk
D
Muller-Wieland
D001665:Binding Sites; D015153:Blotting, Western; D002460:Cell Line; D002851:Chromatography, High Pressure Liquid; D003001:Cloning, Molecular; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D017930:Genes, Reporter; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D008156:Luciferases / Q000378:metabolism; D020935:MAP Kinase Signaling System; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D010455:Peptides / Q000737:chemistry; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D011401:Promoter Regions, Genetic; D017434:Protein Structure, Tertiary; D012694:Serine / Q000737:chemistry*; D051782:Sterol Regulatory Element Binding Protein 2; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation; D014162:Transfection
D004268:DNA-Binding Proteins; D007328:Insulin; D010455:Peptides; C497390:SREBF2 protein, human; D051782:Sterol Regulatory Element Binding Protein 2; D014157:Transcription Factors; D012694:Serine; D004247:DNA; D008156:Luciferases; D020928:Mitogen-Activated Protein Kinases