Recently, secretin has been suggested as a neuropeptide and is be involved in autism and other diseases such as pancreatic adenomas. Thus, its biological functions and relationships with diseases have become a research focus. Therefore, understanding the signal transduction through secretin receptor is a pre-requisite for further investigation and interpretation. Secretin receptor has a relatively large N-terminal domain containing N-glycoslation sites for ligand recognition and conserved cysteine residues for receptor conformations. As one of the G protein coupled receptors, secretin receptor also contains the common molecular architecture of 7 transmembrane domains that intertwined by 3 exoloops and 3 endoloops. These transmemrbane domains were enriched by hydrophobic residues, which help to anchor the receptor into the plasma membrane. Whereas, many conserved basic residues were located in the 2nd and 3rd endoloops and proved to be involved in receptor activation and G protein coupling. Nevertheless, receptor signaling is a complicated process and the interaction and selectivity of G proteins that certainly rely on a combination of functional motifs. For the Carboxyl tail, conflicting research findings were published in the aspect of secretin receptor internalization and desensitization. In this article, we summarize the research studies and implications on function motifs of the secretin receptor and hence provide a general picture on its function.
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