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.
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.
Wang
Yingfei
Y
Institut für Neurobiochemie, Medizinische Fakultät, Otto-von-Guericke-Universität Magdeburg, Leipziger Str. 44, 39120 Magdeburg, Germany.
Luo
Weibo
W
Reiser
Georg
G
D000818:Animals; D001253:Astrocytes / Q000502:physiology*; D001921:Brain / Q000502:physiology*; D002478:Cells, Cultured; D054360:Chemokine CXCL1; D019743:Chemokines, CXC / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation; D005786:Gene Expression Regulation; D020868:Gene Silencing; D006706:Homeostasis; D007770:L-Lactate Dehydrogenase / Q000032:analysis; D048670:MAP Kinase Kinase 4 / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D044463:Receptor, PAR-1 / Q000378:metabolism*; D044464:Receptor, PAR-2 / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction
D054360:Chemokine CXCL1; D019743:Chemokines, CXC; C513297:Cxcl1 protein, rat; D034741:RNA, Small Interfering; D044463:Receptor, PAR-1; D044464:Receptor, PAR-2; D007770:L-Lactate Dehydrogenase; D048670:MAP Kinase Kinase 4