The low-density lipoprotein receptor-related protein is a pro-survival receptor in Schwann cells: possible implications in peripheral nerve injury

J Neurosci. 2006 Oct 25;26(43):11197-207. doi: 10.1523/JNEUROSCI.2709-06.2006.

Abstract

Schwann cells undergo phenotypic modulation in peripheral nerve injury. In the adult rodent, Schwann cells are resistant to death-promoting challenges. The responsible receptors and signaling pathways are incompletely understood. In this study, we demonstrate that low-density lipoprotein receptor-related protein-1 (LRP-1) is expressed in adult sciatic nerve. After crush injury, LRP-1 is lost from the axoplasm and substantially upregulated in Schwann cells. Increased LRP-1 mRNA expression was observed locally at the injury site in multiple forms of sciatic nerve injury, including crush injury, chronic constriction injury, and axotomy. Endogenously produced tumor necrosis factor-alpha (TNF-alpha) was mostly responsible for the increase in LRP-1 expression; this activity was reproduced by direct injection of TNF-alpha into injured nerves in the TNF-alpha gene knock-out mouse. TNF receptor II was primarily involved. TNF-alpha also increased LRP-1 mRNA in Schwann cells in primary culture. Silencing of Schwann cell LRP-1 with siRNA decreased phosphorylated Akt and increased activated caspase-3. Equivalent changes in cell signaling were observed in LRP-1-deficient murine embryonic fibroblasts. Schwann cell death was induced in vitro by serum withdrawal or TNF-alpha, to a greater extent when LRP-1 was silenced. Schwann cell death was induced in vivo by injecting the LRP-1 antagonist, receptor-associated protein, into axotomy sites in adult rats. These results support a model in which LRP-1 functions as a pro-survival receptor in Schwann cells.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Animals, Newborn
  • Cells, Cultured
  • Female
  • Low Density Lipoprotein Receptor-Related Protein-1
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Peripheral Nerves / metabolism
  • Peripheral Nerves / pathology
  • RNA, Messenger / biosynthesis
  • RNA, Messenger / genetics
  • Rats
  • Rats, Sprague-Dawley
  • Receptors, LDL / biosynthesis*
  • Receptors, LDL / genetics
  • Schwann Cells / metabolism*
  • Schwann Cells / pathology
  • Sciatic Neuropathy / genetics
  • Sciatic Neuropathy / metabolism*
  • Sciatic Neuropathy / pathology
  • Tumor Suppressor Proteins / biosynthesis*
  • Tumor Suppressor Proteins / genetics

Substances

  • Low Density Lipoprotein Receptor-Related Protein-1
  • Lrp1 protein, mouse
  • RNA, Messenger
  • Receptors, LDL
  • Tumor Suppressor Proteins