PACAP interacts with PAC1 receptors to induce tissue plasminogen activator (tPA) expression and activity in schwann cell-like cultures

PLoS One. 2015 Feb 6;10(2):e0117799. doi: 10.1371/journal.pone.0117799. eCollection 2015.

Abstract

Regeneration of peripheral nerves depends on the abilities of rejuvenating axons to migrate at the injury site through cellular debris and altered extracellular matrix, and then grow along the residual distal nerve sheath conduit and reinnervate synaptic targets. Considerable evidence suggest that glial cells participate in this process, although the mechanisms remain to be clarified. In cell culture, regenerating neurites secrete PACAP, a peptide shown to induce the expression of the protease tissue plasminogen activator (tPA) in neural cell types. In the present studies, we tested the hypothesis that PACAP can stimulate peripheral glial cells to produce tPA. More specifically, we addressed whether or not PACAP promoted the expression and activity of tPA in the Schwann cell line RT4-D6P2T, which shares biochemical and physical properties with Schwann cells. We found that PACAP dose- and time-dependently stimulated tPA expression both at the mRNA and protein level. Such effect was mimicked by maxadilan, a potent PAC1 receptor agonist, but not by the PACAP-related homolog VIP, suggesting a PAC1-mediated function. These actions appeared to be mediated at least in part by the Akt/CREB signaling cascade because wortmannin, a PI3K inhibitor, prevented peptide-driven CREB phosphorylation and tPA increase. Interestingly, treatment with BDNF mimicked PACAP actions on tPA, but acted through both the Akt and MAPK signaling pathways, while causing a robust increase in PACAP and PAC1 expression. PACAP6-38 totally blocked PACAP-driven tPA expression and in part hampered BDNF-mediated effects. We conclude that PACAP, acting through PAC1 receptors, stimulates tPA expression and activity in a Akt/CREB-dependent manner to promote proteolytic activity in Schwann-cell like cultures.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Brain-Derived Neurotrophic Factor / metabolism
  • Cell Line
  • Dose-Response Relationship, Drug
  • Gene Expression / drug effects*
  • Pituitary Adenylate Cyclase-Activating Polypeptide / pharmacology*
  • Proto-Oncogene Proteins c-akt / metabolism
  • Rats
  • Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide, Type I / metabolism*
  • Schwann Cells / cytology
  • Schwann Cells / drug effects
  • Schwann Cells / metabolism*
  • Signal Transduction / drug effects
  • Tissue Plasminogen Activator / genetics
  • Tissue Plasminogen Activator / metabolism*

Substances

  • Brain-Derived Neurotrophic Factor
  • Pituitary Adenylate Cyclase-Activating Polypeptide
  • Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide, Type I
  • Proto-Oncogene Proteins c-akt
  • Tissue Plasminogen Activator

Grants and funding

This work was supported by a National grant PON01-00110. Part of these experiments were accomplished using scientific equipment provided through a convention with Catania City Hall in the context of the ICT-E1 project. The authors would like to thank Mr P. Asero for his technical support. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.