Interaction with calmodulin is important for the secretion of thimet oligopeptidase following stimulation

Thimet oligopeptidase (THOP 1) distribution in cane toad (Bufo Marinus, Linnaeus, 1758) brain

Thimet oligopeptides (THOP 1) is a metal-dependent peptidase involved in the metabolism of neuropeptides and the presentation of peptides via MHC-1. It has been shown to play a role in the regulation of protein-protein interactions and the metabolism of intracellular peptides. THOP 1 is associated with important biological processes such as metabolism and neurodegenerative diseases, among others. The objective of this study is to elucidate the distribution of THOP 1 in the Bufo marinus brain. The analysis of THOP 1 amino acid sequences indicates that they have been conserved throughout evolution, with significant homology observed across various phyla. When comparing amphibians with other species, more than 70% identity can be identified. Immunohistochemistry analysis of the toad's brain has demonstrated that the enzyme has a ubiquitous distribution, consistent with previous findings in mammals. THOP 1 can be found in important areas of the brain, such as bulb, thalamic nuclei, striatum, hypothalamus, and among others. Nonetheless, THOP 1 is consistently localized within the nucleus, a pattern also observed in the rat brain. Therefore, based on these results, the toad appears to be an excellent model for studying the general biology of THOP 1, given the substantial homology of this enzyme with mammals and its similarity in distribution within the brain.

Probing the Conformational States of Thimet Oligopeptidase in Solution

Thimet oligopeptidase (TOP) is a metallopeptidase involved in the metabolism of oligopeptides inside and outside cells of various tissues. It has been proposed that substrate or inhibitor binding in the TOP active site induces a large hinge-bending movement leading to a closed structure, in which the bound ligand is enclosed. The main goal of the present work was to study this conformational change, and fluorescence techniques were used. Four active TOP mutants were created, each equipped with a single-Trp residue (fluorescence donor) and a p-nitro-phenylalanine (pNF) residue as fluorescence acceptor at opposite sides of the active site. pNF was biosynthetically incorporated with high efficiency using the amber codon suppression technology. Inhibitor binding induced shorter Donor-Acceptor (D-A) distances in all mutants, supporting the view that a hinge-like movement is operative in TOP. The activity of TOP is known to be dependent on the ionic strength of the assay buffer and D-A distances were measured at different ionic strengths. Interestingly, a correlation between the D-A distance and the catalytic activity of TOP was observed: the highest activities corresponded to the shortest D-A distances. In this study for the first time the hinge-bending motion of a metallopeptidase in solution could be studied, yielding insight about the position of the equilibrium between the open and closed conformation. This information will contribute to a more detailed understanding of the mode of action of these enzymes, including therapeutic targets like neurolysin and angiotensin-converting enzyme 2 (ACE2).

The Relevance of Thimet Oligopeptidase in the Regulation of Energy Metabolism and Diet-Induced Obesity

Thimet oligopeptidase (EC 3.4.24.15; EP24.15; THOP1) is a potential therapeutic target, as it plays key biological functions in processing biologically functional peptides. The structural conformation of THOP1 provides a unique restriction regarding substrate size, in that it only hydrolyzes peptides (optimally, those ranging from eight to 12 amino acids) and not proteins. The proteasome activity of hydrolyzing proteins releases a large number of intracellular peptides, providing THOP1 substrates within cells. The present study aimed to investigate the possible function of THOP1 in the development of diet-induced obesity (DIO) and insulin resistance by utilizing a murine model of hyperlipidic DIO with both C57BL6 wild-type (WT) and THOP1 null (THOP1^−/−) mice. After 24 weeks of being fed a hyperlipidic diet (HD), THOP1^−/− and WT mice ingested similar chow and calories; however, the THOP1^−/− mice gained 75% less body weight and showed neither insulin resistance nor non-alcoholic fatty liver steatosis when compared to WT mice. THOP1^−/− mice had increased adrenergic-stimulated adipose tissue lipolysis as well as a balanced level of expression of genes and microRNAs associated with energy metabolism, adipogenesis, or inflammation. Altogether, these differences converge to a healthy phenotype of THOP1^−/− fed a HD. The molecular mechanism that links THOP1 to energy metabolism is suggested herein to involve intracellular peptides, of which the relative levels were identified to change in the adipose tissue of WT and THOP1^−/− mice. Intracellular peptides were observed by molecular modeling to interact with both pre-miR-143 and pre-miR-222, suggesting a possible novel regulatory mechanism for gene expression. Therefore, we successfully demonstrated the previously anticipated relevance of THOP1 in energy metabolism regulation. It was suggested that intracellular peptides were responsible for mediating the phenotypic differences that are described herein by a yet unknown mechanism of action.

Signaling molecules targeting cannabinoid receptors: Hemopressin and related peptides

Cannabinoid receptors (CBRs) are part of the endocannabinoid system, which is involved in various physiological processes such as nociception, inflammation, appetite, stress, and emotion regulation. Many studies have linked the endocannabinoid system to neuroinflammatory and neurodegenerative disorders such as Parkinson's disease, Huntington's chorea, Alzheimer's disease, and multiple sclerosis. Hemopressin [Hp; a fragment of the hemoglobin α1 chain (95-103 amino acids)] and related peptides [VD-Hpα and RVD-Hpα] are peptides that bind to CBRs. Hp acts as an inverse agonist to CB₁ receptor (CB₁R), VD-Hpα acts as an agonist to CB₁R, and RVD-Hpα acts as a negative allosteric modulator of CB₁R and a positive allosteric modulator of CB₂R. Because of the critical roles of CBRs in numerous physiological processes, it is appealing to use Hp and related peptides for therapeutic purposes. This review discusses their discovery, structure, metabolism, brain exposure, self-assembly characteristics, pharmacological characterization, and pharmacological activities.

Similar intracellular peptide profile of TAP1/β2 microglobulin double-knockout mice and C57BL/6 wild-type mice as revealed by peptidomic analysis

Cells produce and use peptides in distinctive ways. In the present report, using isotope labeling plus semi-quantitative mass spectrometry, we evaluated the intracellular peptide profile of TAP1/β2m⁻(/)⁻ (transporter associated with antigen-processing 1/ß2 microglobulin) double-knockout mice and compared it with that of C57BL/6 wild-type animals. Overall, 92 distinctive peptides were identified, and most were shown to have a similar concentration in both mouse strains. However, some peptides showed a modest increase or decrease (~2-fold), whereas a glycine-rich peptide derived from the C-terminal of neurogranin (KGPGPGGPGGAGGARGGAGGGPSGD) showed a substantial increase (6-fold) in TAP1/β2m⁻(/)⁻ mice. Thus, TAP1 and β2microglobulin have a small influence on the peptide profile of neuronal tissue, suggesting that the presence of peptides derived from intracellular proteins in neuronal tissue is not associated with antigens of the class I major histocompatibility complex. Therefore, it is possible that these intracellular peptides play a physiological role.