Glycosylation GPCRs

All of the known class A receptors are subject to posttranslational modification at one or more iV-linked glycosylation sequences, found either in the extracellular amino terminns or in the second exdacellular loop. Glycosylation is required for the expression of some GPCRs at the plasma membrane (12,13). Furthermore, many receptors, snch as rhodopsin and the dopamine receptors, are also subject to other posttranslational modifications, such as palmitoylation at the intracellular domains... 

The cloned receptor cDNA encodes for a protein of 491 amino adds with all the characteristics of a typical GPCR, as there are 7 putative transmembrane domains, N-terminal glycosylation sites and phosphorylation sites for protein kinase A and C (resp PKA and PKC) [11],... 

Fig. 5. Topology and common structural features of GPCRs from class A. The characteristic seven transmembrane domains, which are presumably a-helical, are shown as numbered cylinders TMI-VII. These are connected by intracellular loops ICLI-III and extracellular loops, ECLI-III. A conserved disulfide links ECLI and ECLII. The residues that define common sequence motifs, as discussed in the text, are denoted by white circles. Post-translational glycosylation and palmitoylation modifications are depicted at the N- and C-termini, respectively (see text for additional discussion and references).

The most frequent posttranslational modifications for GPCRs are N-glycosylation at the N-terminus and external loop Asn-X-Ser/Thr sequences (human calcitonin receptor-like receptor [61] and un,-adrenergic receptor [62]), pabnitoylation (human dopamine Di receptor [63]), and phosphorylation ( 2 adrenergic receptor [64]). 

The physiological and pharmacological effects of histamine are mediated through four different receptors Hi, Hj, Hj, and Ht, all members of the 7-transmembrane g protein-coupled receptor (GPCR) family with amino terminal glycosylation sites and phosphorylation sites for protein kinases A and C. The receptors are widely expressed on different tissues that are responsive to histamine. For the Hi receptor these tissues include smooth muscle cells of the airways and vasculature, the gastrointestinal tract, cardiovascular system, neutrophils, endothelial cells, T and B cells, hepatocy tes, nerve... 

The physiological and pharmacological effects of histamine are mediated throngh four different receptors Hi, H2, H3, and Ht, all members of the 7-ttansmembrane g protein-conpled receptor (GPCR) family with amino terminal glycosylation sites and phosphorylation sites for protein kinases A and C. 

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