Evidence of functional modulation of the MEKK/JNK/cJun signaling cascade by the low density lipoprotein receptor-related protein (LRP).
Lipoprotein receptors, such as LRP, have been shown to assemble multiprotein complexes containing intracellular signaling molecules; however, in vivo, their signaling function is poorly understood. Using a novel LRP receptor fusion construct, a type I transmembrane protein chimera, termed sIgG-LRP (bearing the intracellular COOH-terminal tail of human LRP as recombinant fusion to a transmembrane region plus the extracellular IgG-F(c) domain), we here investigated LRP signal transduction specificity in intact cells. First and similar to activated alpha2-macroglobulin as agonist of endogenous LRP, expression of sIgG-LRP demonstrated significant apoptosis protection. Second and similar to alpha2-macroglobulin-induced endogenous LRP, sIgG-LRP is sufficient to negatively modulate mitogen-induced Elk-1 and cJun (but not NF-kappaB) transcriptional activity. Third, expression of sIgG-LRP also impaired cJun transactivation mediated by constitutive active mutants of Rac-1 and MEKK-1. Fourth and unexpectedly, sIgG-LRP expression was found to be associated with a marked enhancement of mitogen-induced cJun amino-terminal kinase (JNK) activation. Fifth, confocal microscopic examination and subcellular fractionation demonstrated that sIgG-LRP and JNK co-localize in transfected cells. Therefore, sIgG-LRP expression was found to significantly impair activation-induced translocation of JNK into the nucleus. Taken together, we here demonstrate that sIgG-LRP protein sequesters activated JNK into the plasma membrane compartment in intact cells, inhibiting nuclear activation of the JNK-dependent transcription factors Elk-1 and cJun.
Institute for Medical Biology and Human Genetics, the Institute for Medical Chemistry and Biochemistry, University of Innsbruck, Innsbruck, Austria A6020.
Christina
C
Lutz
Johannes
J
Nimpf
Marcel
M
Jenny
Karl
K
Boecklinger
Christiane
C
Enzinger
Gerd
G
Utermann
Gabriele
G
Baier-Bitterlich
Gottfried
G
Baier
D000818:Animals; D002166:Camptothecin / Q000494:pharmacology; D002531:Cerebellum / Q000187:drug effects / Q000502:physiology; D017931:DNA Primers; D004268:DNA-Binding Proteins; D004742:Enhancer Elements, Genetic; D017930:Genes, Reporter; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases; D019169:Jurkat Cells; D007700:Kinetics; D026563:LDL-Receptor Related Protein-Associated Protein / Q000235:genetics / Q000494:pharmacology*; D048728:MAP Kinase Kinase Kinase 1; D020935:MAP Kinase Signaling System / Q000187:drug effects* / Q000502:physiology; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D020932:Nerve Growth Factor / Q000494:pharmacology; D016716:PC12 Cells; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D051381:Rats; D011994:Recombinant Proteins / Q000494:pharmacology*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014157:Transcription Factors / Q000235:genetics; D015533:Transcriptional Activation; D014162:Transfection; D000511:alpha-Macroglobulins / Q000494:pharmacology; D020830:rac1 GTP-Binding Protein / Q000378:metabolism
D017931:DNA Primers; D004268:DNA-Binding Proteins; C052130:GAL4 protein, S cerevisiae; D026563:LDL-Receptor Related Protein-Associated Protein; D016755:Proto-Oncogene Proteins c-jun; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D000511:alpha-Macroglobulins; D020932:Nerve Growth Factor; D017346:Protein Serine-Threonine Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048728:MAP Kinase Kinase Kinase 1; C482576:MAP3K1 protein, human; D020830:rac1 GTP-Binding Protein; D013755:Tetradecanoylphorbol Acetate; D002166:Camptothecin