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pubmed:abstractText |
The glucagon receptor is a member of the G protein-coupled receptor superfamily. Since several G protein-coupled receptors undergo phosphorylation in response to agonist, we investigated the phosphorylation of the glucagon receptor following the addition of glucagon to a Chinese hamster ovary cell line expressing the human glucagon receptor (CHO/hGR). Glucagon induced a rapid, time and concentration-dependent phosphorylation of its receptor on serine residues. Neither forskolin nor phorbol ester increased receptor phosphorylation, suggesting that cAMP-dependent protein kinase and protein kinase C do not catalyze this phosphorylation event. Furthermore, two mutant cell lines expressing glucagon receptors with successively truncated receptor cytoplasmic tails were tested. A strong correlation between the number of potential phosphorylation sites, receptor phosphorylation and receptor internalization was observed, suggesting that phosphorylation of the glucagon receptor in CHO/hGR cells is functionally linked to its internalization.
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