期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2021
卷号：118
期号：32
DOI：10.1073/pnas.2101279118
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Significance
The high-resolution cryogenic electron microscopy structure of the human parathyroid hormone receptor 2 (PTH2R), in complex with an endogenous tuberoinfundibular peptide (TIP39) and a heterotrimeric G
s protein, reveals that the unique loop conformation at the N terminus of TIP39 is indispensable for PTH2R activation, as the deletion of which results in a potent PTH2R antagonist TIP(7-39). The naturally occurring mutation G258D impairs the receptor signaling such as cAMP accumulation. This finding provides a potential molecular mechanism for syndromic short stature.
The parathyroid hormone receptor 2 (PTH2R) is a class B1 G protein–coupled receptor (GPCR) involved in the regulation of calcium transport, nociception mediation, and wound healing. Naturally occurring mutations in PTH2R were reported to cause hereditary diseases, including syndromic short stature. Here, we report the cryogenic electron microscopy structure of PTH2R bound to its endogenous ligand, tuberoinfundibular peptide (TIP39), and a heterotrimeric G
s protein at a global resolution of 2.8 Å. The structure reveals that TIP39 adopts a unique loop conformation at the N terminus and deeply inserts into the orthosteric ligand-binding pocket in the transmembrane domain. Molecular dynamics simulation and site-directed mutagenesis studies uncover the basis of ligand specificity relative to three PTH2R agonists, TIP39, PTH, and PTH-related peptide. We also compare the action of TIP39 with an antagonist lacking six residues from the peptide N terminus, TIP(7-39), which underscores the indispensable role of the N terminus of TIP39 in PTH2R activation. Additionally, we unveil that a disease-associated mutation G258D significantly diminished cAMP accumulation induced by TIP39. Together, these results not only provide structural insights into ligand specificity and receptor activation of class B1 GPCRs but also offer a foundation to systematically rationalize the available pharmacological data to develop therapies for various disorders associated with PTH2R.
关键词：enparathyroid hormone receptor 2;cryo-electron microscopy;G protein–coupled receptor;ligand recognition;syndromic short stature
