Myroilysin Is a New Bacterial Member of the M12A Family of Metzincin Metallopeptidases and Is Activated by a Cysteine Switch Mechanism

Sast1-mediated manifold effects inhibit Plutella xylostella fertility

BACKGROUND

Plutella xylostella (Linnaeus) is a destructive pest of cruciferous crops due to its strong reproductive capacity and extensive resistance to pesticides. Seminal fluid proteins (SFPs) are the main effective factors that determine the reproductive physiology and behaviour of both sexes. Although an increasing number of SFPs have been identified, the effects of astacins in SFPs on agricultural pests have not yet been reported. Here, we elucidated the mechanisms by which Sast1 (seminal astacin 1) regulates the fertility of Plutella xylostella (L.).

RESULTS

PxSast1 was specifically expressed in the testis and accesssory gland. CRISPR/Cas9-induced PxSast1 knockout successfully constructed two homozygous mutant strains. Sast1 impaired the fertility of P. xylostella by separately regulating the reproductive capacity of males and females. Loss of PxSast1, on the one hand, significantly decreased the ability of males to mate and fertilize, mainly manifested as shortened mating duration, reduced mating competitiveness and decreased eupyrene sperm production; on the other hand, it significantly inhibited the expression of chorion genes in females, resulting in oogenesis deficits. Simultaneously, for mated females, the differentially expressed genes in signalling pathways related to oogenesis and chorion formation were significantly enriched after PxSast1 knockout.

CONCLUSION

These analyses of the functions of PxSast1 as the regulator of spermatogenesis and oogenesis establish its importance in the fertility process of P. xylostella, as well as its potential as a promising target for genetic regulation-based pest control. © 2024 Society of Chemical Industry.

Matrix metalloproteinases as attractive therapeutic targets for chronic pain: A narrative review

Chronic pain constitutes an abnormal pain state that detrimentally affects the quality of life, daily activities, occupational performance, and stability of mood. Despite the prevalence of chronic pain, effective drugs with potent abirritation and minimal side effects remain elusive. Substantial studies have revealed aberrant activation of the matrix metalloproteinases (MMPs) in multiple chronic pain models. Additionally, emerging evidence has demonstrated that the downregulation of MMPs can alleviate chronic pain in diverse animal models, underscoring the unique and crucial role of MMPs in different stages and types of chronic pain. This review delves into the mechanistic insights and roles of MMPs in modulating chronic pain. The aberrant activation of MMPs has been linked to neuropathic pain through mechanisms involving myelin abnormalities in peripheral nerve and spinal dorsal horn (SDH), hyperexcitability of dorsal root ganglion (DRG) neurons, activation of N-methyl-d-aspartate receptors (NMDAR) and Ca2+-dependent signals, glial cell activation, and proinflammatory cytokines release. Different MMPs also contribute significantly to inflammatory pain and cancer pain. Furthermore, we summarized the substantial therapeutic potential of MMP pharmacological inhibitors across different types of chronic pain. Overall, our findings underscore the promising therapeutic prospects of MMPs targeting for managing chronic pain.

Structural and evolutionary insights into astacin metallopeptidases

The astacins are a family of metallopeptidases (MPs) that has been extensively described from animals. They are multidomain extracellular proteins, which have a conserved core architecture encompassing a signal peptide for secretion, a prodomain or prosegment and a zinc-dependent catalytic domain (CD). This constellation is found in the archetypal name-giving digestive enzyme astacin from the European crayfish Astacus astacus. Astacin catalytic domains span ∼200 residues and consist of two subdomains that flank an extended active-site cleft. They share several structural elements including a long zinc-binding consensus sequence (HEXXHXXGXXH) immediately followed by an EXXRXDRD motif, which features a family-specific glutamate. In addition, a downstream SIMHY-motif encompasses a "Met-turn" methionine and a zinc-binding tyrosine. The overall architecture and some structural features of astacin catalytic domains match those of other more distantly related MPs, which together constitute the metzincin clan of metallopeptidases. We further analysed the structures of PRO-, MAM, TRAF, CUB and EGF-like domains, and described their essential molecular determinants. In addition, we investigated the distribution of astacins across kingdoms and their phylogenetic origin. Through extensive sequence searches we found astacin CDs in > 25,000 sequences down the tree of life from humans beyond Metazoa, including Choanoflagellata, Filasterea and Ichtyosporea. We also found < 400 sequences scattered across non-holozoan eukaryotes including some fungi and one virus, as well as in selected taxa of archaea and bacteria that are pathogens or colonizers of animal hosts, but not in plants. Overall, we propose that astacins originate in the root of Holozoa consistent with Darwinian descent and that the latter genes might be the result of horizontal gene transfer from holozoan donors.

Zymogenic latency in an ∼250-million-year-old astacin metallopeptidase

The horseshoe crab Limulus polyphemus is one of few extant Limulus species, which date back to ∼250 million years ago under the conservation of a common Bauplan documented by fossil records. It possesses the only proteolytic blood-coagulation and innate immunity system outside vertebrates and is a model organism for the study of the evolution and function of peptidases. The astacins are a family of metallopeptidases that share a central ∼200-residue catalytic domain (CD), which is found in >1000 species across holozoans and, sporadically, bacteria. Here, the zymogen of an astacin from L. polyphemus was crystallized and its structure was solved. A 34-residue, mostly unstructured pro-peptide (PP) traverses, and thus blocks, the active-site cleft of the CD in the opposite direction to a substrate. A central `PP motif' (F35-E-G-D-I39) adopts a loop structure which positions Asp38 to bind the catalytic metal, replacing the solvent molecule required for catalysis in the mature enzyme according to an `aspartate-switch' mechanism. Maturation cleavage of the PP liberates the cleft and causes the rearrangement of an `activation segment'. Moreover, the mature N-terminus is repositioned to penetrate the CD moiety and is anchored to a buried `family-specific' glutamate. Overall, this mechanism of latency is reminiscent of that of the other three astacins with known zymogenic and mature structures, namely crayfish astacin, human meprin β and bacterial myroilysin, but each shows specific structural characteristics. Remarkably, myroilysin lacks the PP motif and employs a cysteine instead of the aspartate to block the catalytic metal.

Protease-triggered bioresponsive drug delivery for the targeted theranostics of malignancy

Proteases have a fundamental role in maintaining physiological homeostasis, but their dysregulation results in severe activity imbalance and pathological conditions, including cancer onset, progression, invasion, and metastasis. This striking importance plus superior biological recognition and catalytic performance of proteases, combining with the excellent physicochemical characteristics of nanomaterials, results in enzyme-activated nano-drug delivery systems (nanoDDS) that perform theranostic functions in highly specific response to the tumor phenotype stimulus. In the tutorial review, the key advances of protease-responsive nanoDDS in the specific diagnosis and targeted treatment for malignancies are emphatically classified according to the effector biomolecule types, on the premise of summarizing the structure and function of each protease. Subsequently, the incomplete matching and recognition between enzyme and substrate, structural design complexity, volume production, and toxicological issues related to the nanocomposites are highlighted to clarify the direction of efforts in nanotheranostics. This will facilitate the promotion of nanotechnology in the management of malignant tumors.

Structure-based mechanism of cysteine-switch latency and of catalysis by pappalysin-family metallopeptidases

Tannerella forsythia is an oral dysbiotic periodontopathogen involved in severe human periodontal disease. As part of its virulence factor armamentarium, at the site of colonization it secretes mirolysin, a metallopeptidase of the unicellular pappalysin family, as a zymogen that is proteolytically auto-activated extracellularly at the Ser54-Arg55 bond. Crystal structures of the catalytically impaired promirolysin point mutant E225A at 1.4 and 1.6 Å revealed that latency is exerted by an N-terminal 34-residue pro-segment that shields the front surface of the 274-residue catalytic domain, thus preventing substrate access. The catalytic domain conforms to the metzincin clan of metallopeptidases and contains a double calcium site, which acts as a calcium switch for activity. The pro-segment traverses the active-site cleft in the opposite direction to the substrate, which precludes its cleavage. It is anchored to the mature enzyme through residue Arg21, which intrudes into the specificity pocket in cleft sub-site S1'. Moreover, residue Cys23 within a conserved cysteine-glycine motif blocks the catalytic zinc ion by a cysteine-switch mechanism, first described for mammalian matrix metallopeptidases. In addition, a 1.5 Å structure was obtained for a complex of mature mirolysin and a tetradecapeptide, which filled the cleft from sub-site S1' to S6'. A citrate molecule in S1 completed a product-complex mimic that unveiled the mechanism of substrate binding and cleavage by mirolysin, the catalytic domain of which was already preformed in the zymogen. These results, including a preference for cleavage before basic residues, are likely to be valid for other unicellular pappalysins derived from archaea, bacteria, cyanobacteria, algae and fungi, including archetypal ulilysin from Methanosarcina acetivorans. They may further apply, at least in part, to the multi-domain orthologues of higher organisms.

Multiple Architectures and Mechanisms of Latency in Metallopeptidase Zymogens

Metallopeptidases cleave polypeptides bound in the active-site cleft of catalytic domains through a general base/acid mechanism. This involves a solvent molecule bound to a catalytic zinc and general regulation of the mechanism through zymogen-based latency. Sixty reported structures from 11 metallopeptidase families reveal that prosegments, mostly N-terminal of the catalytic domain, block the cleft regardless of their size. Prosegments may be peptides (5-14 residues), which are only structured within the zymogens, or large moieties (<227 residues) of one or two folded domains. While some prosegments globally shield the catalytic domain through a few contacts, others specifically run across the cleft in the same or opposite direction as a substrate, making numerous interactions. Some prosegments block the zinc by replacing the solvent with particular side chains, while others use terminal α-amino or carboxylate groups. Overall, metallopeptidase zymogens employ disparate mechanisms that diverge even within families, which supports that latency is less conserved than catalysis.

Continuous Automated Model EvaluatiOn (CAMEO) complementing the critical assessment of structure prediction in CASP12

Every second year, the community experiment "Critical Assessment of Techniques for Structure Prediction" (CASP) is conducting an independent blind assessment of structure prediction methods, providing a framework for comparing the performance of different approaches and discussing the latest developments in the field. Yet, developers of automated computational modeling methods clearly benefit from more frequent evaluations based on larger sets of data. The "Continuous Automated Model EvaluatiOn (CAMEO)" platform complements the CASP experiment by conducting fully automated blind prediction assessments based on the weekly pre-release of sequences of those structures, which are going to be published in the next release of the PDB Protein Data Bank. CAMEO publishes weekly benchmarking results based on models collected during a 4-day prediction window, on average assessing ca. 100 targets during a time frame of 5 weeks. CAMEO benchmarking data is generated consistently for all participating methods at the same point in time, enabling developers to benchmark and cross-validate their method's performance, and directly refer to the benchmarking results in publications. In order to facilitate server development and promote shorter release cycles, CAMEO sends weekly email with submission statistics and low performance warnings. Many participants of CASP have successfully employed CAMEO when preparing their methods for upcoming community experiments. CAMEO offers a variety of scores to allow benchmarking diverse aspects of structure prediction methods. By introducing new scoring schemes, CAMEO facilitates new development in areas of active research, for example, modeling quaternary structure, complexes, or ligand binding sites.