Discordance between GLP-1R gene and protein expression in mouse pancreatic islet cells.
The insulinotropic actions of glucagon-like peptide 1 receptor (GLP-1R) in β-cells have made it a useful target to manage type 2 diabetes. Metabolic stress reduces β-cell sensitivity to GLP-1, yet the underlying mechanisms are unknown. We hypothesized that Glp1r expression is heterogeneous among β-cells and that metabolic stress decreases the number of GLP-1R-positive β-cells. Here, analyses of publicly available single-cell RNA-Seq sequencing (scRNASeq) data from mouse and human β-cells indicated that significant populations of β-cells do not express the Glp1r gene, supporting heterogeneous GLP-1R expression. To check these results, we used complementary approaches employing FACS coupled with quantitative RT-PCR, a validated GLP-1R antibody, and flow cytometry to quantify GLP-1R promoter activity, gene expression, and protein expression in mouse α-, β-, and δ-cells. Experiments with Glp1r reporter mice and a validated GLP-1R antibody indicated that >90% of the β-cells are GLP-1R positive, contradicting the findings with the scRNASeq data. α-cells did not express Glp1r mRNA and δ-cells expressed Glp1r mRNA but not protein. We also examined the expression patterns of GLP-1R in mouse models of metabolic stress. Multiparous female mice had significantly decreased β-cell Glp1r expression, but no reduction in GLP-1R protein levels or GLP-1R-mediated insulin secretion. These findings suggest caution in interpreting the results of scRNASeq for low-abundance transcripts such as the incretin receptors and indicate that GLP-1R is widely expressed in β-cells, absent in α-cells, and expressed at the mRNA, but not protein, level in δ-cells.
['Gray|Sarah M|SM|0000-0003-2370-7968', 'Xin|Yurong|Y|', 'Ross|Elizabeth C|EC|', 'Chazotte|Bryanna M|BM|', 'Capozzi|Megan E|ME|', 'El|Kimberley|K|0000-0002-5550-1684', 'Svendsen|Berit|B|0000-0002-3604-000X', 'Ravn|Peter|P|', 'Sloop|Kyle W|KW|', 'Tong|Jenny|J|', 'Gromada|Jesper|J|', 'Campbell|Jonathan E|JE|0000-0003-4358-6331', "D'Alessio|David A|DA|"]
D000818:Animals D002478:Cells, Cultured D015870:Gene Expression D000067757:Glucagon-Like Peptide-1 Receptor D006801:Humans D050417:Insulin-Secreting Cells D051379:Mice D008810:Mice, Inbred C57BL D059010:Single-Cell Analysis
islet glucagon-like peptide 1 receptor (GLP-1R) metabolism heterogeneity GLP-1R antibody flow cytometry incretin G protein–coupled receptor (GPCR) cell sorting glucose-dependent insulinotropic polypeptide receptor (GIPR)