Notch Signal Mediates the Cross-Interaction between M2 Muscarinic Acetylcholine Receptor and Neuregulin/ErbB Pathway: Effects on Schwann Cell Proliferation.

Roberta Piovesana,Simona Loreti,Ruggero Ricordy,Ada Maria Tata,Claudio Talora,Annalinda Pisano

doi:10.3390/biom12020239

Abstract

The cross-talk between axon and glial cells during development and in adulthood is mediated by several molecules. Among them are neurotransmitters and their receptors, which are involved in the control of myelinating and non-myelinating glial cell development and physiology. Our previous studies largely demonstrate the functional expression of cholinergic muscarinic receptors in Schwann cells. In particular, the M2 muscarinic receptor subtype, the most abundant cholinergic receptor expressed in Schwann cells, inhibits cell proliferation downregulating proteins expressed in the immature phenotype and triggers promyelinating differentiation genes. In this study, we analysed the in vitro modulation of the Neuregulin-1 (NRG1)/erbB pathway, mediated by the M2 receptor activation, through the selective agonist arecaidine propargyl ester (APE). M2 agonist treatment significantly downregulates NRG1 and erbB receptors expression, both at transcriptional and protein level, and causes the internalization and intracellular accumulation of the erbB2 receptor. Additionally, starting from our previous results concerning the negative modulation of Notch-active fragment NICD by M2 receptor activation, in this work, we clearly demonstrate that the M2 receptor subtype inhibits erbB2 receptors by Notch-1/NICD downregulation. Our data, together with our previous results, demonstrate the existence of a cross-interaction between the M2 receptor and NRG1/erbB pathway-Notch1 mediated, and that it is responsible for the modulation of Schwann cell proliferation/differentiation.

Highlights

In recent decades, several studies have highlighted the importance of neuron-glia cross-talk in the regulation of axonal conduction, synaptic transmission and glial differentiation [1,2,3]
In order to explain the mechanism responsible for this effect, we firstly evaluated the ability of M2 agonist arecaidine propargyl ester (APE) to counteract Schwann cells (SCs) proliferation induced by PE/NRG1
SCs maintained in FBS and forskolin, showed the typical cell proliferating profile, with a percentage of S phase of 16,41% ± 3.36%, whereas, after PE exposure, the percentages were 21,15 ± 2,4% after 16 h, 24,95 ± 0,85% after 24 h and 17,13 ± 0,46% after 48 h, supporting the idea that PE has a positive effect on SC proliferation

Summary

Introduction

Several studies have highlighted the importance of neuron-glia cross-talk in the regulation of axonal conduction, synaptic transmission and glial differentiation [1,2,3]. 3, -4) encoded by four distinct genes [5] They bind with different affinity the epidermal growth factor receptors, erbB [6]. NRG1, the most characterized NRG member, can be produced in three different isoforms (types I, II, and III) derived by alternative splicing from the same gene. It can be produced as soluble membrane-bound protein that can be released as paracrine factor after being cleaved by proteases, or remain on the cell surface where it mediates juxtacrine interactions [7]. Because different NRG1 isoforms can be produced and many of these can be released, the erbB receptors may receive this paracrine signal directly by neighbouring cells. The same cell can produce and receive the NRG signal in an autocrine manner

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