title: The regions within the N-terminus critical for human glucagon like peptide-1 receptor (hGLP-1R) cell surface expression.
abstract: The hGLP-1R is a target for the treatment of type 2 diabetes and belongs to the class B family of GPCRs. Like other class B GPCRs, the GLP-1R contains an N-terminal signal peptide (SP) and undergoes N-linked glycosylation, which are important for its trafficking and maturation. This study analysed the role of the SP, the hydrophobic region after the SP (HRASP), glycosylation and the conserved residues within the N-terminus in GLP-1R trafficking. HGLP-1R targeted to the cell surface showed no SP, and the SP deleted mutant, but not the mutants defective in SP cleavage, showed cell surface expression, demonstrating the importance of SP cleavage for hGLP-1R cell surface expression. The N-terminal deletions of hGLP-1R revealed that the HRASP, not the SP, is essential for cell surface expression of GLP-1R. Further, inhibition of hGLP-1R glycosylation prevented cell surface expression of the receptor. Mutation of Trp(39), Tyr(69) and Tyr(88), which are required for agonist binding, in the GLP-1R abolished cell surface expression of the receptor independent of the SP cleavage or N-linked glycosylation. In conclusion, the N-terminus of hGLP-1R regulates receptor trafficking and maturation. Therefore this study provides insight into the role of hGLP-1R N-terminus on the receptor cell surface expression.
authors.affiliation: Institute of Life Science 1, College of Medicine, Swansea University, Singleton Park, Swansea, SA2 8PP, UK.
authors.forename: Aiysha
authors.initials: A
authors.lastname: Thompson
authors.affiliation: Institute of Life Science 1, College of Medicine, Swansea University, Singleton Park, Swansea, SA2 8PP, UK.
authors.forename: Venkateswarlu
authors.initials: V
authors.lastname: Kanamarlapudi
mesh_terms: D000595:Amino Acid Sequence; D002462:Cell Membrane / Q000378:metabolism; D017124:Conserved Sequence; D000067757:Glucagon-Like Peptide-1 Receptor; D006031:Glycosylation; D057809:HEK293 Cells; D006801:Humans; D011499:Protein Processing, Post-Translational; D021382:Protein Sorting Signals; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D059748:Proteolysis; D018027:Receptors, Glucagon / Q000737:chemistry / Q000378:metabolism*
chemical_list: C000593833:GLP1R protein, human; D000067757:Glucagon-Like Peptide-1 Receptor; D021382:Protein Sorting Signals; D018027:Receptors, Glucagon