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Internalization and homologous desensitization of the GLP-1 receptor depend on phosphorylation of the receptor carboxyl tail at the same three sites.

  • 1997-07-01
Published in:
  • Molecular endocrinology (Baltimore, Md.). - 1997
Amino Acid Sequence
Animals
Binding Sites
CHO Cells
COS Cells
Cricetinae
Cyclic AMP
Endocytosis
Fibroblasts
Glucagon-Like Peptide 1
Glucagon-Like Peptide-1 Receptor
Kinetics
Molecular Sequence Data
Peptides
Phosphorylation
Protein Kinase C
Receptors, Glucagon
Recombinant Proteins
Sequence Deletion
Serine
English Homologous desensitization and internalization of the GLP-1 receptor correlate with phosphorylation of the receptor in a 33-amino acid segment of the cytoplasmic tail. Here, we identify the sites of phosphorylation as being three serine doublets located at positions 441/442, 444/445, and 451/452. The role of phosphorylation on homologous desensitization was assessed after stable expression in fibroblasts of the wild type or of mutant receptors in which phosphorylation sites were changed in various combinations to alanines. We showed that desensitization, as measured by a decrease in the maximal production of cAMP after a first exposure of the cells to GLP-1, was strictly dependent on phosphorylation. Furthermore, the number of phosphorylation sites correlated with the extent of desensitization with no, intermediate, or maximal desensitization observed in the presence of one, two, or three phosphorylation sites, respectively. Internalization of the receptor-ligand complex was assessed by measuring the rate of internalization of bound [125I]GLP-1 or the redistribution of the receptor to an endosomal compartment after agonist binding. Our data demonstrate that internalization was prevented in the absence of receptor phosphorylation and that intermediate rates of endocytosis were obtained with receptors containing one or two phosphorylation sites. Thus, homologous desensitization and internalization require phosphorylation of the receptor at the same three sites. However, the differential quantitative impairment of these two processes in the single and double mutants suggests different molecular mechanisms controlling desensitization and internalization.
Language
  • English
Open access status
bronze
Identifiers
Persistent URL
https://folia.unifr.ch/global/documents/130623
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