Evidence of functional modulation of the MEKK/JNK/cJun signaling cascade by the low density lipoprotein receptor-related protein (LRP)

J Biol Chem. 2002 Nov 8;277(45):43143-51. doi: 10.1074/jbc.M204426200. Epub 2002 Aug 21.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Camptothecin / pharmacology
  • Cerebellum / drug effects
  • Cerebellum / physiology
  • DNA Primers
  • DNA-Binding Proteins
  • Enhancer Elements, Genetic
  • Genes, Reporter
  • Humans
  • JNK Mitogen-Activated Protein Kinases
  • Jurkat Cells
  • Kinetics
  • LDL-Receptor Related Protein-Associated Protein / genetics
  • LDL-Receptor Related Protein-Associated Protein / pharmacology*
  • MAP Kinase Kinase Kinase 1*
  • MAP Kinase Signaling System / drug effects*
  • MAP Kinase Signaling System / physiology
  • Mitogen-Activated Protein Kinases / metabolism
  • Nerve Growth Factor / pharmacology
  • PC12 Cells
  • Polymerase Chain Reaction
  • Promoter Regions, Genetic
  • Protein-Serine-Threonine Kinases / metabolism
  • Proto-Oncogene Proteins c-jun / metabolism
  • Rats
  • Recombinant Proteins / pharmacology*
  • Saccharomyces cerevisiae Proteins / genetics
  • Tetradecanoylphorbol Acetate / pharmacology
  • Transcription Factors / genetics
  • Transcriptional Activation
  • Transfection
  • alpha-Macroglobulins / pharmacology
  • rac1 GTP-Binding Protein / metabolism

Substances

  • DNA Primers
  • DNA-Binding Proteins
  • GAL4 protein, S cerevisiae
  • LDL-Receptor Related Protein-Associated Protein
  • Proto-Oncogene Proteins c-jun
  • Recombinant Proteins
  • Saccharomyces cerevisiae Proteins
  • Transcription Factors
  • alpha-Macroglobulins
  • Nerve Growth Factor
  • Protein-Serine-Threonine Kinases
  • JNK Mitogen-Activated Protein Kinases
  • Mitogen-Activated Protein Kinases
  • MAP Kinase Kinase Kinase 1
  • MAP3K1 protein, human
  • rac1 GTP-Binding Protein
  • Tetradecanoylphorbol Acetate
  • Camptothecin