Molecular insights into differentiated ligand recognition of the human parathyroid hormone receptor 2

The parathyroid hormone receptor 2 (PTH2R) is a class B1 G protein-coupled receptor (GPCR) involved in 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 cryo-electron microscopy structure of PTH2R bound to its endogenous ligand, tuberoinfundibular peptide (TIP39), and a heterotrimeric Gs protein at a global resolution of 2.8 Å. The structure reveals that TIP39 adopts a unique loop conformation at N terminus and deeply inserts into the orthosteric ligand-binding pocket in the transmembrane (TM) domain. Molecular dynamics (MD) simulation and site-directed mutagenesis studies uncover the basis of ligand specificity relative to three PTH2R agonists, TIP39, PTH, and PTH-related peptide (PTHrP). 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 novel therapies for various disorders associated with PTH2R.

The Parathyroid Hormone and Peptides Like It. Literature Review

Wide prevalence of the parathyroid glands pathology and the need for new methods of diagnosis and treatment are forcing researchers all over the world to go more deeply into the pathophysiological mechanisms. A parathyroid hormone (PTH) is main cause of mineral disorders. In addition, humans have a family with similar in structure molecules that contribute to the maintenance of calcium and phosphate homeostasis. The family includes PTH, parathyroid hormone-related protein (PTHrP) and tuberoinfundibular peptide 39 (TIP39, also known as PTH2). The genes encoding these peptides have highly homologous amino acid regions in the N-(amino) terminal receptor-binding sites of each family member, as well as the preserved structure of their organization, which seems to be due to the presence of one parent gene. The variety of classical and “non-classical” effects allows to expand the understanding of these substances and consider them as hormones that go beyond the regulation of phosphorus-calcium metabolism. The review provides information on the structure and biosynthesis of these peptides, as well as a wide range of their effects on the human body.

NEUROCHEMICAL ASSESSMENT AND BEHAVIORAL ROLE OF TUBEROINFUNDIBULAR PEPTIDE-39 IN ACUTE RESTRAINT STRESS-INDUCED DEPRESSION IN RATS.

Objective: Tuberoinfundibular peptide of 39 (TIP39) is a potent agonist to the parathyroid hormone 2 receptor (PTH2R) abundantly expressed in brain. The current study focused to evaluate the role of TIP39 in acute restraint stress (ARS)-induced depression model.Methods: Rats were exposed to ARS for 2 h to establish the depression and then subjected to open field and forced swim test (OFT and FST). TIP39 (1 and 10 nmol/rat) and HYWH (1 nmol/rat) are a PTH2R antagonist which was infused through intracerebroventricular route. Diazepam (2 mg/kg, i.p) was utilized as reference standard.Results: The results depict ARS significantly diminished the TIP39 expression in cerebral regions and causes depression-like behavior. TIP39 significantly decreased the immobility period in FST. In the OFT, TIP39 significantly increased the ambulatory activity and did not alter the rearing and grooming activity in comparison to ARS group. After TIP39 treatment, plasma noradrenaline levels were significantly increased, whereas the serotonin levels were unaltered. The corticosterone levels also decreased significantly. In rat brain tissues, TIP39 significantly reversed the abnormalities in glutamate and gamma-aminobutyric acid (GABA) level by ARS induction. In contrast, HYWH-treated rats did not show any significant variations in the neurochemical and behavioral parameters in comparison to ARS rats.Conclusion: Our reports submitted that the primary evidence depicting the stimulation of TIP39 expression could modulate the monoaminergic, GABAergic, and glutaminergic release with the support of hypothalamic-pituitary-adrenal axis that can be produced an antidepressant-like effect evident with the interactive study.

NEUROCHEMICAL ASSESSMENT AND BEHAVIORAL ROLE OF TUBEROINFUNDIBULAR PEPTIDE-39 IN ACUTE RESTRAINT STRESS-INDUCED DEPRESSION IN RATS.

Objective: Tuberoinfundibular peptide of 39 (TIP39) is a potent agonist to the parathyroid hormone 2 receptor (PTH2R) abundantly expressed in brain. The current study focused to evaluate the role of TIP39 in acute restraint stress (ARS)-induced depression model.Methods: Rats were exposed to ARS for 2 h to establish the depression and then subjected to open field and forced swim test (OFT and FST). TIP39 (1 and 10 nmol/rat) and HYWH (1 nmol/rat) are a PTH2R antagonist which was infused through intracerebroventricular route. Diazepam (2 mg/kg, i.p) was utilized as reference standard.Results: The results depict ARS significantly diminished the TIP39 expression in cerebral regions and causes depression-like behavior. TIP39 significantly decreased the immobility period in FST. In the OFT, TIP39 significantly increased the ambulatory activity and did not alter the rearing and grooming activity in comparison to ARS group. After TIP39 treatment, plasma noradrenaline levels were significantly increased, whereas the serotonin levels were unaltered. The corticosterone levels also decreased significantly. In rat brain tissues, TIP39 significantly reversed the abnormalities in glutamate and gamma-aminobutyric acid (GABA) level by ARS induction. In contrast, HYWH-treated rats did not show any significant variations in the neurochemical and behavioral parameters in comparison to ARS rats.Conclusion: Our reports submitted that the primary evidence depicting the stimulation of TIP39 expression could modulate the monoaminergic, GABAergic, and glutaminergic release with the support of hypothalamic-pituitary-adrenal axis that can be produced an antidepressant-like effect evident with the interactive study.

Relationship between seminal plasma tuberoinfundibular peptide of 39 residues and sperm functional attributes in buffalo (Bubalus bubalis)

The buffalo seminal plasma protein profile and its relationship with sperm quality have not been studied in detail. Thus, the aim of the present study was to profile buffalo seminal plasma proteins and to assess the relationship between differentially expressed proteins and sperm characteristics. Semen samples (n = 44) were collected from 11 Murrah buffalo bulls (four ejaculates from each animal) and seminal plasma protein profiling was performed by sodium dodecyl sulfate–polyacrylamide gel electrophoresis. Matrix-assisted laser desorption ionisation time-of-flight analysis of one of the differentially expressed proteins, namely the 11–12 kDa protein, identified it as tuberoinfundibular peptide of 39 residues (TIP39). Western blot analysis confirmed the presence of TIP39, with TIP39 expression in seminal plasma varying among bulls. Based on TIP39 levels, bulls were classified into two groups, those with high and low protein. The percentages of spermatozoa positive for mitochondrial membrane potential test, chromatin distribution test, synthetic media sperm penetrability test and acrosomal integrity test were significantly (P < 0.05) high in the high protein group. The present study is the first to demonstrate the presence of TIP39 in buffalo seminal plasma and the positive effect of TIP39 on the functional parameters and fertilising ability of spermatozoa.