Combinatorial expression of GPCR isoforms affects signalling and drug responses

Abstract

G protein-coupled receptors (GPCRs) are transmembrane proteins that modulate physiology across diverse tissues in response to extracellular signals. GPCR signalling can differ due to variation in the sequence (e.g. polymorphisms) or in the expression of receptors in different tissues. The resulting differences in response are an important source of physiological signalling bias. An underexplored source of such bias is the generation of functionally diverse GPCR isoforms that can have distinct patterns of expression in human tissues. Here, we report the findings from a comprehensive study, integrating data from human tissue-level transcriptomes, GPCR sequences and structures, functional annotations, proteomics, single-cell RNA sequencing, population-wide genetic association studies, and pharmacological experiments. Our results show how a single GPCR gene can diversify into multiple isoforms with distinct structural and signalling properties, and how unique combinations of these isoforms can be expressed in different human tissues, contributing to differences in physiological signalling. Based on their structural changes and expression patterns, some of the detected isoforms may also influence drug response and represent new drug targets with improved tissue selectivity. Our findings highlight the need to move from a canonical to a context-specific view of GPCR signalling, in which one considers how the combinatorial expression of receptor isoforms in a specific system (i.e. a particular cell type, tissue, or organism) collectively impacts receptor signalling. These observations pave the way for understanding the impact of isoform variation on GPCR signalling response and have implications for exploiting such variation as a source of GPCR selectivity in drug development.

Comprehensive single-cell gene and isoform expression analysis reveals signatures of ageing in haematopoietic stem and progenitor cells

“…AS is thought to occur in at least 62% of multi-exonic genes in mouse 6 and up to 95% of multi-exonic genes in human 7 . Increasingly, there is an understanding that isoform (co-)expression in tissues and cells can reveal previously unseen complexities in cell signalling responses, as was demonstrated recently for G-protein coupled receptors 8 .…”

Serotonin GPCR-based biosensing modalities in yeast

“…GPCR single-nucleotide polymorphisms (SNPs) are known to impact EC 50 and agonist sensitivities in humans (Marti-Solano et al, 2020), and human variants of 5HT1a and MOR1 expressed in yeast have previously shown to reproduce Gα-dependent sensitivities to serotonin and morphine, respectively, as reported from mammalian cells (Bean et al, 2021;Nakamura et al, 2015).…”

Splicing and editing of ionotropic glutamate receptors: a comprehensive analysis based on human RNA-Seq data

“…S17) 1 splice sites different from canonical transcript (C = novel combination); 2 state: C = characterized; T = part of annotated transcript; N = new junction; P = described but not detected (n.d.); 3 abundance rel. to canonical junction/s (global = across all datasets; max = maximal local abundance); 4 potential NMD transcript: exon junction complex (EJC) more than 50 nt downstream of termination codon; 5 PAS = polyadenylation signal; 6 based on coverage analysis due to lack of a specific splice junction; 7 junction does not fulfill relevance criteria (supplementary junction);…”

“…Splicing and RNA editing are important mechanisms to increase protein diversity and to adjust gene expression in a context-dependent manner. Splicing and editing are particularly widespread in the central nervous system (CNS) [1], where they contribute to differentiation [2,3], synaptic organization [4], and the tuning of voltage-gated channels and receptors [5][6][7]. One important receptor family is the family of ionotropic glutamate receptors (iGluRs).…”