Neuropeptidase activity is down-regulated by estradiol in steroid-sensitive regions of the hypothalamus in female mice

Substrate-like novel inhibitors of prolyl specific oligo peptidase for neurodegenerative disorders

Prolyl specific oligopeptidase (POP), is one of the highly expressed enzymes in the brain and is a prime target to treat disorders related to the central nervous system. Here, we describe the structure-based design of the tacrine derivatives, selective, and brain-permeable POP inhibitors. These compounds inactivate POP in-vitro specifically and sustainably at very low concentrations (nano molar). Among this series, compound 6b (IC50 = 0.81 ± 0.04 µM) exhibited most potent inhibition. Furthermore, kinetic study revealed that these molecules target active site of POP which is further confirmed by in-silico molecular interaction analysis. The computational docking results indicates that the compounds are well fitted in the active site with high binding score (i.e., > -7 to > -4 kcal/mol) where Trp595, Arg643, Tyr473, and Ser554 plays important role in binding with the active compounds. The molecular dynamic simulation of most active compounds (6a, 6b, 6d, and 6f) displayed higher free energy binding, when compared to the standard drug in MM-PBSA based binding free energy calculation. In addition, the predicted pharmacokinetic profile suggests that these compounds can serve as excellent inhibitors upon additional optimization which makes them prime choice for further investigation.Communicated by Ramaswamy H. Sarma.

Thimet Oligopeptidase—A Classical Enzyme with New Function and New Form

Peptidases generate bioactive peptides that can regulate cell signaling and mediate intercellular communication. While the processing of peptide precursors is initiated intracellularly, some modifications by peptidases may be conducted extracellularly. Thimet oligopeptidase (TOP) is a peptidase that processes neuroendocrine peptides with roles in mood, metabolism, and immune responses, among other functions. TOP also hydrolyzes angiotensin I to angiotensin 1–7, which may be involved in the pathophysiology of COVID-19 infection. Although TOP is primarily cytosolic, it can also be associated with the cell plasma membrane or secreted to the extracellular space. Recent work indicates that membrane-associated TOP can be released with extracellular vesicles (EVs) to the extracellular space. Here we briefly summarize the enzyme’s classical function in extracellular processing of neuroendocrine peptides, as well as its more recently understood role in intracellular processing of various peptides that impact human diseases. Finally, we discuss new findings of EV-associated TOP in the extracellular space.

Sleep deprivation changes thimet oligopeptidase (THOP1) expression and activity in rat brain

The consequences of sleep deprivation on memory, cognition, nociception, stress, and endocrine function are related to the balance of neuropeptides, with peptidases being particularly essential. Thimet oligopeptidase (THOP1) is a metallopeptidase implicated in the metabolism of many sleep-related peptides, including angiotensin I, gonadotropin releasing hormone (GnRH), neurotensin, and opioid peptides. In the present study, we evaluated the effect of sleep deprivation and sleep recovery in male rats on THOP1 expression and specific activity in the central nervous system. In the striatum and hypothalamus, THOP1 activity decreased following sleep deprivation and a recovery period. Meanwhile, THOP1 activity and immunoexpression increased in the hippocampal dentate gyrus during the sleep recovery period. Changes in THOP1 expression after sleep deprivation and during sleep recovery can potentially alter the processing of neuropeptides. In particular, processing of opioid peptides may be related to the known increase in pain sensitivity in this model. These results suggest that THOP1 may be an important player in the effects of sleep deprivation.

Neuropeptidome of the Hypothalamus and Pituitary Gland of Indicine × Taurine Heifers: Evidence of Differential Neuropeptide Processing in the Pituitary Gland before and after Puberty

Puberty in cattle is regulated by an endocrine axis, which includes a complex milieu of neuropeptides in the hypothalamus and pituitary gland. The neuropeptidome of hypothalamic-pituitary gland tissue of pre- (PRE) and postpubertal (POST) Bos indicus-influenced heifers was characterized, followed by quantitative analysis of 51 fertility-related neuropeptides in these tissues. Comparison of peptide abundances with gene expression levels allowed assessment of post-transcriptional peptide processing. On the basis of classical cleavage, 124 mature neuropeptides from 35 precursor proteins were detected in hypothalamus and pituitary gland tissues of three PRE and three POST Brangus heifers. An additional 19 peptides (cerebellins, PEN peptides) previously reported as neuropeptides that did not follow classical cleavage were also identified. In the pre-pubertal hypothalamus, a greater diversity of neuropeptides (25.8%) was identified relative to post-pubertal heifers, while in the pituitary gland, 38.6% more neuropeptides were detected in the post-pubertal heifers. Neuro-tissues of PRE and POST heifers revealed abundance differences ( p < 0.05) in peptides from protein precursors involved in packaging and processing (e.g., the granin family and ProSAAS) or neuron stimulation (PENK, CART, POMC, cerebellins). On their own, the transcriptome data of the precursor genes could not predict the neuropeptide profile in the exact same tissues in several cases. This provides further evidence of the importance of differential processing of the neuropeptide precursors in the pituitary before and after puberty.

EP24.15 as a Potential Regulator of Kisspeptin Within the Neuroendocrine Hypothalamus

The neuropeptide kisspeptin (Kiss1) is integral to the advent of puberty and the generation of cyclical LH surges. Although many complex actions of Kiss1 are known, the mechanisms governing the processing/regulation of this peptide have not been unveiled. The metallo enzyme, endopeptidase 24.15 (thimet oligopeptidase), has been demonstrated to play a key role in the processing and thus the duration of action of the reproductive neuropeptide, GnRH, which signals downstream of Kiss1. Initial in silico modeling implied that Kiss1 could also be a putative substrate for EP24.15. Coincubation of Kiss1 and EP24.15 demonstrated multiple cleavages of the peptide predominantly between Arg29-Gly30 and Ser47-Phe48 (corresponding to Ser5-Phe6 in Kiss-10; Kiss-10 as a substrate had an additional cleavage between Phe6-Gly7) as determined by mass spectrometry. Vmax for the reaction was 2.37±0.09 pmol/min · ng with a Km of 19.68 ± 2.53μM, which is comparable with other known substrates of EP24.15. EP24.15 immunoreactivity, as previously demonstrated, is distributed in cell bodies, nuclei, and processes throughout the hypothalamus. Kiss1 immunoreactivity is localized primarily to cell bodies and fibers within the mediobasal and anteroventral-periventricular hypothalamus. Double-label immunohistochemistry indicated coexpression of EP24.15 and Kiss1, implicating that the regulation of Kiss1 by EP24.15 could occur in vivo. Further studies will be directed at determining the precise temporal sequence of EP24.15 effects on Kiss1 as it relates to the control of reproductive hormone secretion and treatment of fertility issues.