Endothelin B Receptors on Primary Chicken Müller Cells and the Human MIO-M1 Müller Cell Line Activate ERK Signaling via Transactivation of Epidermal Growth Factor Receptors

Abstract

Injury to the eye or retina triggers Müller cells, the major glia cell of the retina, to dedifferentiate and proliferate. In some species they attain retinal progenitor properties and have the capacity to generate new neurons. The epidermal growth factor receptor (EGFR) system and extracellular signal-regulated kinase (ERK) signaling are key regulators of these processes in Müller cells. The extracellular signals that modulate and control these processes are not fully understood. In this work we studied whether endothelin receptor signaling can activate EGFR and ERK signaling in Müller cells. Endothelin expression is robustly upregulated at retinal injury and endothelin receptors have been shown to transactivate EGFRs in other cell types. We analyzed the endothelin signaling system in chicken retina and cultured primary chicken Müller cells as well as the human Müller cell line MIO-M1. The Müller cells were stimulated with receptor agonists and treated with specific blockers to key enzymes in the signaling pathway or with siRNAs. We focused on endothelin receptor mediated transactivation of EGFRs by using western blot analysis, quantitative reverse transcriptase PCR and immunocytochemistry. The results showed that chicken Müller cells and the human Müller cell line MIO-M1 express endothelin receptor B. Stimulation by the endothelin receptor B agonist IRL1620 triggered phosphorylation of ERK1/2 and autophosphorylation of (Y1173) EGFR. The effects could be blocked by Src-kinase inhibitors (PP1, PP2), EGFR-inhibitor (AG1478), EGFR-siRNA and by inhibitors to extracellular matrix metalloproteinases (GM6001), consistent with a Src-kinase mediated endothelin receptor response that engage ligand-dependent and ligand-independent EGFR activation. Our data suggest a mechanism for how injury-induced endothelins, produced in the retina, may modulate the Müller cell responses by Src-mediated transactivation of EGFRs. The data give support to a view in which endothelins among several other functions, serve as an injury-signal that regulate the gliotic response of Müller cells.

Targeting endothelin receptor signalling overcomes heterogeneity driven therapy failure

“…In order to dissect how EDNRA signals to ERK and hence regulates cell growth, we used different kinase inhibitors and found that while a PKC inhibitor did not impact on the protective function of EDN1, inhibiting RAF kinases with RAF265 or blocking RTK activity using the pan RTK inhibitor dovitinib overcame this protection (Fig EV5H and I). This suggests a crosstalk between EDNRA and RTK signalling as it has been described previously (Harada et al , ; Harun‐Or‐Rashid et al , ; Moody et al , ), which ultimately activates ERK through RAF.…”

7,8-Dihydroxiflavone Protects Adult Rat Axotomized Retinal Ganglion Cells through MAPK/ERK and PI3K/AKT Activation

“…This overexpression is mainly observed in the GCL where the end feet of MCs reside [ 52 ] and close to the damaged RGCs, as shown in Figure 2 and Figure 4 . Thus, it is tempting to suggest that the activation of the survival MAPK signaling pathway results in neuroprotection through activation of both MCs and RGCs, as has been described in other experimental models such as NMDA excitotoxicity [ 53 , 54 ], or retinal detachment, ischemia-reperfusion, inflammation and glaucoma (reviewed in [ 55 ]). P-MAPK and MAPK was also observed in the outer retina; however, further studies are need to understand this event.…”

Lineage-specific intersection of endothelin and GDNF signaling in enteric nervous system development

“…In a variety of ways, RTK signaling can require mediation by G protein coupled receptors, a mechanisms called transactivation (Kilpatrick & Hill, 2021). Prior in vitro explant studies have implicated a convergence of Ret and Ednrb at the level of protein kinase A activity ( (Barlow et al, 2003;Goto et al, 2013); see also Discussion), although other mechanisms of transactivation have been described for Ednrb to other RTKs (Grantcharova et al, 2006;Harun-Or-Rashid, Konjusha, Galindo-Romero, & Hallbook, 2016), and Ret with other GPCRs (Tsuchioka, Takebayashi, Hisaoka, Maeda, & Nakata, 2008). Because Ret expression was preserved in Wnt1Cre-derived enteric progenitors even as they were nonresponsive to GDNF, we considered that transactivation via Ednrb might be involved.…”