The Orphan G Protein-coupled Receptor GPR17 Negatively Regulates Oligodendrocyte Differentiation via Gαi/o and Its Downstream Effector Molecules

Katharina Simon,Stephanie Hennen,Nicole Merten,Stefanie Blättermann,Michel Gillard,Evi Kostenis,Jesus Gomeza

doi:10.1074/jbc.m115.683953

Abstract

Recent studies have recognized G protein-coupled receptors as important regulators of oligodendrocyte development. GPR17, in particular, is an orphan G protein-coupled receptor that has been identified as oligodendroglial maturation inhibitor because its stimulation arrests primary mouse oligodendrocytes at a less differentiated stage. However, the intracellular signaling effectors transducing its activation remain poorly understood. Here, we use Oli-neu cells, an immortalized cell line derived from primary murine oligodendrocytes, and primary rat oligodendrocyte cultures as model systems to identify molecular targets that link cell surface GPR17 to oligodendrocyte maturation blockade. We demonstrate that stimulation of GPR17 by the small molecule agonist MDL29,951 (2-carboxy-4,6-dichloro-1H-indole-3-propionic acid) decreases myelin basic protein expression levels mainly by triggering the Gαi/o signaling pathway, which in turn leads to reduced activity of the downstream cascade adenylyl cyclase-cAMP-PKA-cAMP response element-binding protein (CREB). In addition, we show that GPR17 activation also diminishes myelin basic protein abundance by lessening stimulation of the exchange protein directly activated by cAMP (EPAC), thus uncovering a previously unrecognized role for EPAC to regulate oligodendrocyte differentiation. Together, our data establish PKA and EPAC as key downstream effectors of GPR17 that inhibit oligodendrocyte maturation. We envisage that treatments augmenting PKA and/or EPAC activity represent a beneficial approach for therapeutic enhancement of remyelination in those demyelinating diseases where GPR17 is highly expressed, such as multiple sclerosis.

Highlights

Myelination is a central nervous system (CNS) process where oligodendrocytes establish myelin sheaths that stabilize, pro
Activation of GPR17 by MDL29,951 Triggers G␣q and G␣i/o Signaling Pathways in Differentiating Oli-neu Cells—To assess which intracellular pathways are utilized by GPR17 to regulate oligodendrocyte maturation, we selected as cellular models primary rat oligodendrocyte cultures and the murine oligodendroglial precursor cell line, Oli-neu, which undergoes differentiation into myelin basic protein (MBP)-expressing cells upon induction by different chemical treatments [17]
The present study demonstrates that stimulation of GPR17 by the small molecule agonist MDL29,951 diminishes oligodendrocyte differentiation through the G␣i/o signaling pathway, reducing the activity of the downstream cAMP-specific effectors protein kinase A (PKA) and exchange protein directly activated by cAMP (EPAC) and leading to decreased cellular abundance of the myelination marker MBP

Summary

Introduction

Myelination is a central nervous system (CNS) process where oligodendrocytes establish myelin sheaths that stabilize, pro-. Activation of GPR17 by MDL29,951 Triggers G␣q and G␣i/o Signaling Pathways in Differentiating Oli-neu Cells—To assess which intracellular pathways are utilized by GPR17 to regulate oligodendrocyte maturation, we selected as cellular models primary rat oligodendrocyte cultures and the murine oligodendroglial precursor cell line, Oli-neu, which undergoes differentiation into MBP-expressing cells upon induction by different chemical treatments [17].

Results

Conclusion