title: The putative signal peptide of glucagon-like peptide-1 receptor is not required for receptor synthesis but promotes receptor expression.
abstract: GLP-1R (glucagon-like peptide-1 receptor) mediates the 'incretin effect' and many other anti-diabetic actions of its cognate ligand, GLP-1 (glucagon-like peptide-1). It belongs to the class B family of GPCRs (G protein-coupled receptors) and possesses an N-terminal putative SP (signal peptide). It has been reported that this sequence is required for the synthesis of GLP-1R and is cleaved after receptor synthesis. In the present study, we conducted an in-depth exploration towards the role of the putative SP in GLP-1R synthesis. A mutant GLP-1R without this sequence was expressed in HEK293 cells (human embryonic kidney 293 cells) and displayed normal functionality with respect to ligand binding and activation of adenylate cyclase. Thus the putative SP does not seem to be required for receptor synthesis. Immunoblotting analysis shows that the amount of GLP-1R synthesized in HEK293 cells is low when the putative SP is absent. This indicates that the role of the sequence is to promote the expression of GLP-1R. Furthermore, epitopes tagged at the N-terminal of GLP-1R are detectable by immunofluorescence and immunoblotting in our experiments. In conclusion, the present study points to different roles of SP in GLP-1R expression which broadens our understanding of the functionality of this putative SP of GLP-1R and possibly other Class B GPCRs.
authors.affiliation: *The National Center for Drug Screening and the CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China.
authors.forename: Yunjun
authors.initials: Y
authors.lastname: Ge
authors.affiliation: *The National Center for Drug Screening and the CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China.
authors.forename: Dehua
authors.initials: D
authors.lastname: Yang
authors.affiliation: *The National Center for Drug Screening and the CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China.
authors.forename: Antao
authors.initials: A
authors.lastname: Dai
authors.affiliation: *The National Center for Drug Screening and the CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China.
authors.forename: Caihong
authors.initials: C
authors.lastname: Zhou
authors.affiliation: *The National Center for Drug Screening and the CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China.
authors.forename: Yue
authors.initials: Y
authors.lastname: Zhu
authors.affiliation: *The National Center for Drug Screening and the CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China.
authors.forename: Ming-Wei
authors.initials: MW
authors.lastname: Wang
mesh_terms: D000595:Amino Acid Sequence; D015870:Gene Expression; D052216:Glucagon-Like Peptide 1 / Q000378:metabolism; D000067757:Glucagon-Like Peptide-1 Receptor; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D015151:Immunoblotting; D008024:Ligands; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D009154:Mutation; D011485:Protein Binding; D021382:Protein Sorting Signals / Q000235:genetics*; D018027:Receptors, Glucagon / Q000235:genetics* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: C000593833:GLP1R protein, human; D000067757:Glucagon-Like Peptide-1 Receptor; D008024:Ligands; D021382:Protein Sorting Signals; D018027:Receptors, Glucagon; D049452:Green Fluorescent Proteins; D052216:Glucagon-Like Peptide 1