The Functional Role of the Second NPXY Motif of the LRP1 Beta-Chain in Tissue-Type Plasminogen Activator-Mediated Activation of N-methyl-D-aspartate Receptors

J Biol Chem. 2008 May 2;283(18):12004-13. doi: 10.1074/jbc.M707607200. Epub 2008 Mar 5.

Abstract

The low density lipoprotein receptor-related protein 1 (LRP1) emerges to play fundamental roles in cellular signaling pathways in the brain. One of its prominent ligands is the serine proteinase tissue-type plasminogen activator (tPA), which has been shown to act as a key activator of neuronal mitogen-activated protein kinase pathways via the N-methyl-D-aspartate (NMDA) receptor. However, here we set out to examine whether LRP1 and the NMDA receptor might eventually act in a combined fashion to mediate tPA downstream signaling. By blocking tPA from binding to LRP1 using the receptor-associated protein, we were able to completely inhibit NMDA receptor activation. Additionally, inhibition of NMDA receptor calcium influx with MK-801 resulted in dramatic reduction of tPA-mediated downstream signaling. This indicates a functional interaction between the two receptors, since both experimental approaches resulted in strongly reduced calcium influx and Erk1/2 phosphorylation. Additionally, we were able to inhibit Erk1/2 activation by competing for the LRP1 C-terminal binding motif with a truncated PSD95 construct resembling its PDZ III domain. Furthermore, we identified the distal NPXY amino acid motif in the C terminus of LRP1 as the crucial element for LRP1-NMDA receptor interaction via the adaptor protein PSD95. These results provide new insights into the mechanism of a tPA-induced, LRP1-mediated gating mechanism for NMDA receptors.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Motifs*
  • Amino Acid Sequence
  • Animals
  • Calcium / metabolism
  • Cell Line
  • Disks Large Homolog 4 Protein
  • Enzyme Activation / drug effects
  • Guanylate Kinases
  • Humans
  • Intracellular Signaling Peptides and Proteins / chemistry
  • Intracellular Space / drug effects
  • Intracellular Space / metabolism
  • Low Density Lipoprotein Receptor-Related Protein-1 / antagonists & inhibitors
  • Low Density Lipoprotein Receptor-Related Protein-1 / chemistry*
  • Membrane Proteins / chemistry
  • Mice
  • Mitogen-Activated Protein Kinase 1 / metabolism
  • Mitogen-Activated Protein Kinase 3 / metabolism
  • Neurons / drug effects
  • Neurons / enzymology
  • Phosphorylation / drug effects
  • Plasmids / genetics
  • Plasmids / metabolism
  • Protein Structure, Secondary
  • RNA, Small Interfering / metabolism
  • Rats
  • Rats, Sprague-Dawley
  • Receptor Cross-Talk / drug effects
  • Receptors, N-Methyl-D-Aspartate / metabolism*
  • Signal Transduction / drug effects
  • Structure-Activity Relationship
  • Tissue Plasminogen Activator / pharmacology*

Substances

  • Disks Large Homolog 4 Protein
  • Dlg4 protein, mouse
  • Intracellular Signaling Peptides and Proteins
  • Low Density Lipoprotein Receptor-Related Protein-1
  • Membrane Proteins
  • RNA, Small Interfering
  • Receptors, N-Methyl-D-Aspartate
  • Mitogen-Activated Protein Kinase 1
  • Mitogen-Activated Protein Kinase 3
  • Guanylate Kinases
  • Tissue Plasminogen Activator
  • Calcium