CRELD1 is an evolutionarily-conserved maturational enhancer of ionotropic acetylcholine receptors.

Manuela D'Alessandro,Thomas Boulin,Christian Stigloher,Jean-Louis Bessereau,Janet E Richmond,Vincent Gache,Magali Richard

doi:10.7554/elife.39649

Abstract

The assembly of neurotransmitter receptors in the endoplasmic reticulum limits the number of receptors delivered to the plasma membrane, ultimately controlling neurotransmitter sensitivity and synaptic transfer function. In a forward genetic screen conducted in the nematode C. elegans, we identified crld-1 as a gene required for the synaptic expression of ionotropic acetylcholine receptors (AChR). We demonstrated that the CRLD-1A isoform is a membrane-associated ER-resident protein disulfide isomerase (PDI). It physically interacts with AChRs and promotes the assembly of AChR subunits in the ER. Mutations of Creld1, the human ortholog of crld-1a, are responsible for developmental cardiac defects. We showed that Creld1 knockdown in mouse muscle cells decreased surface expression of AChRs and that expression of mouse Creld1 in C. elegans rescued crld-1a mutant phenotypes. Altogether these results identify a novel and evolutionarily-conserved maturational enhancer of AChR biogenesis, which controls the abundance of functional receptors at the cell surface.

Highlights

The total amount or neurotransmitter receptors synthesized within a neuron or a muscle cell determines the size of the receptor pool that can be delivered to the plasma membrane and, the responsiveness of the cell to specific transmitters
To identify genes regulating the activity of L-acetylcholine receptors (AChR) in C. elegans, we used Mos1-mediated insertional mutagenesis (Boulin and Bessereau, 2007; Williams et al, 2005) and screened for mutants with only partially decreased sensitivity to levamisole, because screens for complete resistance are likely saturated
RT-PCR analysis of the crld-1(kr133) transcripts revealed that cryptic splice donor sites present in the Mos1 kr133 transposon were used at low frequency to generate inframe mRNAs (Figure 1—figure supplement 1)

Summary

Introduction

The total amount or neurotransmitter receptors synthesized within a neuron or a muscle cell determines the size of the receptor pool that can be delivered to the plasma membrane and, the responsiveness of the cell to specific transmitters. The main tobacco component responsible for smoking addiction (Picciotto and Mineur, 2014; Subramaniyan and Dani, 2015), was demonstrated to bind early AChR assembly intermediates in the ER and promote receptor maturation by acting as a pharmacological chaperone. This effect partly accounts for the upregulation of AChR expression caused by chronic exposure to nicotine in the brain (Sallette et al, 2005; Henderson and Lester, 2015). We demonstrate that crld-1 is required for AChR biogenesis and behaves as a maturational enhancer by promoting the assembly of L-AChR subunits in the ER

Results

Discussion

Materials and methods

Funding Funder