Proteinase-activated receptor-1 and -2 Induce the Release of Chemokine GRO/CINC-1 From Rat Astrocytes via Differential Activation of JNK Isoforms, Evoking Multiple Protective Pathways in Brain

Biochem J. 2007 Jan 1;401(1):65-78. doi: 10.1042/BJ20060732.

Abstract

Activation of both PAR-1 (proteinase-activated receptor-1) and PAR-2 resulted in release of the chemokine GRO (growth-regulated oncogene)/CINC-1 (cytokine-induced neutrophil chemoattractant-1), a functional counterpart of human interleukin-8, from rat astrocytes. Here, we investigate whether the two PAR receptor subtypes can signal separately. PAR-2-induced GRO/CINC-1 release was independent of protein kinase C, phosphoinositide 3-kinase and MEK (mitogen-activated protein kinase kinase)-1/2 activation, whereas these three kinases were involved in PAR-1-induced GRO/CINC-1 release. Despite such clear differences between PAR-1 and PAR-2 signalling pathways, JNK (c-Jun N-terminal kinase) was identified in both signalling pathways to play a pivotal role. By isoform-specific loss-of-function studies using small interfering RNA against JNK1-3, we demonstrate that different JNK isoforms mediated GRO/CINC-1 secretion, when it was induced by either PAR-1 or PAR-2 activation. JNK2 and JNK3 isoforms were both activated by PAR-1 and essential for chemokine GRO/CINC-1 secretion, whereas PAR-1-mediated JNK1 activation was mainly responsible for c-Jun phosphorylation, which was not involved in GRO/CINC-1 release. In contrast, PAR-2-induced JNK1 activation, which failed to phosphorylate c-Jun, uniquely contributed to GRO/CINC-1 release. Therefore our results show for the first time that JNK-mediated chemokine GRO/CINC-1 release occurred in a JNK isoform-dependent fashion and invoked PAR subtype-specific mechanisms. Furthermore, here we demonstrate that activation of PAR-2, as well as PAR-1, rescued astrocytes from ceramide-induced apoptosis via regulating chemokine GRO/CINC-1 release. Taken together, our results suggest that PAR-1 and PAR-2 have overlapping functions, but can activate separate pathways under certain pathological conditions to rescue neural cells from cell death. This provides new functional insights into PAR/JNK signalling and the protective actions of PARs in brain.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Astrocytes / physiology*
  • Brain / physiology*
  • Cells, Cultured
  • Chemokine CXCL1
  • Chemokines, CXC / genetics
  • Chemokines, CXC / metabolism*
  • Enzyme Activation
  • Gene Expression Regulation
  • Gene Silencing
  • Homeostasis
  • L-Lactate Dehydrogenase / analysis
  • MAP Kinase Kinase 4 / genetics
  • MAP Kinase Kinase 4 / metabolism*
  • RNA, Small Interfering / genetics
  • Rats
  • Receptor, PAR-1 / metabolism*
  • Receptor, PAR-2 / metabolism*
  • Reverse Transcriptase Polymerase Chain Reaction

Substances

  • Chemokine CXCL1
  • Chemokines, CXC
  • Cxcl1 protein, rat
  • RNA, Small Interfering
  • Receptor, PAR-1
  • Receptor, PAR-2
  • L-Lactate Dehydrogenase
  • MAP Kinase Kinase 4