A comparative analysis of human and mouse islet G-protein coupled receptor expression

Stefan Amisten,Bo Liu,Albert Salehi,Shanta J Persaud,Min Zhao,Patricio Atanes,Guo Cai Huang,Fariborz Parandeh,Inmaculada Ruz-Maldonado,Ross Hawkes

doi:10.1038/srep46600

Abstract

G-protein coupled receptors (GPCRs) are essential for islet function, but most studies use rodent islets due to limited human islet availability. We have systematically compared the GPCR mRNA expression in human and mouse islets to determine to what extent mouse islets can be used as surrogates for human islets to study islet GPCR function, and we have identified species-specific expression of several GPCRs. The A3 receptor (ADORA3) was expressed only in mouse islets and the A3 agonist MRS 5698 inhibited glucose-induced insulin secretion from mouse islets, with no effect on human islets. Similarly, mRNAs encoding the galanin receptors GAL1 (GALR1), GAL2 (GALR2) and GAL3 GALR3) were abundantly expressed in mouse islets but present only at low levels in human islets, so that it reads (GALR3) and galanin inhibited insulin secretion only from mouse islets. Conversely, the sst1 receptor (SSTR1) was abundant only in human islets and its selective activation by CH 275 inhibited insulin secretion from human islets, with no effect on mouse islets. Our comprehensive human and mouse islet GPCR atlas has demonstrated that species differences do exist in islet GPCR expression and function, which are likely to impact on the translatability of mouse studies to the human context.

Highlights

MT1 receptors, which are activated by the pineal hormone melatonin, are reported to be expressed by rodent β-cells but not by human β-cells[16], and different classes of purinergic receptor regulate intracellular calcium levels in rodent[17] and human[18] β-cells
The Quantitative real-time PCR (qPCR) analyses indicated that transcripts encoding 183 G-protein coupled receptors (GPCRs) of the 341 GPCR mRNAs analysed (53.7%) were expressed at levels greater than 0.001% of the mean mRNA expression of the reference genes Actb, Gapdh, Ppia, Tbp and Tfrc in islets isolated from ICR and C57 mice
There were 52 fewer GPCRs expressed by C57 mouse islets (227 GPCR mRNAs vs 279 in C57 islets), there was a strong correlation between the expression patterns based on their levels relative to the reference genes (r2 = 0.95)

Summary

Results

Expression of GPCR mRNAs in islets isolated from C57 and ICR mice. The qPCR analyses indicated that transcripts encoding 183 GPCRs of the 341 GPCR mRNAs analysed (53.7%) were expressed at levels greater than 0.001% of the mean mRNA expression of the reference genes Actb, Gapdh, Ppia, Tbp and Tfrc in islets isolated from ICR and C57 mice. The enrichment of mRNAs encoding these 121 GPCRs in human and mouse islets was determined relative to mRNA expression levels of the five reference genes to allow direct comparison of GPCR expression patterns between species (Fig. 4a,b). This indicated that a large number of GPCR mRNAs are expressed by both human and mouse islets, there are significant species differences in their abundance. MRNAs encoding the GAL1 (GALR1), GAL2 (GALR2) and GAL3 (GALR3), CELSR1, adenosine A3 (ADORA3), LPA6 (LPAR6) and GPR85 receptors were abundantly expressed in mouse islets but were either absent or expressed at very low level in human islets (Supplementary Figure 1). Functional evaluation of the sst[1] receptor agonist CH 275 indicated that it significantly inhibited insulin secretion from human islets, but it had no effect on insulin release from mouse islets (Fig. 8a,b)

Discussion

Author Contributions

Additional Information