Cathepsin D (CD) plays an important role in both biological and pathological processes, although the cleavage characteristics and substrate selection of CD have yet to be fully explored. We employed ...liquid chromatography-tandem mass spectrometry (LC-MS/MS) to identify the CD cleavage sites in bovine serum albumin (BSA). We found that the hydrophobic residues at P1 were not only a preferential factor for CD cleavage but that the hydrophobicity at P1' also contributed to CD recognition. The concept of hydrophobic scores of neighbors (HSN) was proposed to describe the hydrophobic microenvironment of CD recognition sites. The survey of CD cleavage characteristics in several proteins suggested that the HSN was a sensitive indicator for judging the favorable sites in peptides for CD cleavage, with HSN values of 0.5-1.0 representing a likely threshold. Ovalbumin (OVA), a protein resistant to CD cleavage in its native state, was easily cleaved by CD after denaturation, and the features of the cleaved peptides were quite similar to those found in BSA, where a higher HSN value indicated greater cleavability. We further conducted two-dimensional gel electrophoresis (2DE) to find more proteins that were insensitive to CD cleavage in CD-knockdown cells. Based on an analysis of secondary and three-dimensional structures, we postulated that intact proteins with a structure consisting of all α-helices would be relatively accessible to CD cleavage.
Expression of the downstream regulatory element antagonist modulator (DREAM) protein in dorsal root ganglia and spinal cord is related to endogenous control mechanisms of acute and chronic pain. In ...primary sensory trigeminal neurons, high levels of endogenous DREAM protein are preferentially localized in the nucleus, suggesting a major transcriptional role. Here, we show that transgenic mice expressing a dominant active mutant of DREAM in trigeminal neurons show increased responses following orofacial sensory stimulation, which correlates with a decreased expression of prodynorphin and brain‐derived neurotrophic factor in trigeminal ganglia. Genome‐wide analysis of trigeminal neurons in daDREAM transgenic mice identified cathepsin L and the monoglyceride lipase as two new DREAM transcriptional targets related to pain. Our results suggest a role for DREAM in the regulation of trigeminal nociception.
This article is part of the special article series “Pain”.
Molecular mechanisms regulating trigeminal pain are poorly understood. This lack of basic knowledge is unfortunately reflected in the substantial lack of effective treatment for trigeminal pain. We found that transcriptional repressor DREAM regulates the expression of several pain‐related genes in trigeminal neurons and control trigeminal pain perception. Inhibition of DREAM activity might represent a new therapeutical venue. MGLL, monoglyceride lipase; CTSL, cathepsin L, pDyn, prodynorphin; daDREAM, dominant active DREAM.
This article is part of the special article series “Pain”.
Muscle deterioration caused by endogenous enzymes can greatly impact the quality of shrimp products during their processing and storage. In this study, the changes in trypsin, calpain, and cathepsin ...activity and their effects on muscle proteins in the intact and beheaded shrimp during 120 days of frozen storage were investigated. The results showed that the hardness, stretching force, chewiness, myofibrillar protein (MP) content, and Ca2+-ATPase activity significantly decreased in both the intact and beheaded shrimp samples with the prolonged storage period. Notably, the beheaded shrimp exhibited more stable characteristics than the intact shrimp samples throughout frozen storage. The endogenous enzyme analysis showed that the variations in the trypsin, calpain, and cathepsin activities were significantly pronounced in the intact shrimp compared to those in the beheaded samples. Furthermore, the myofibrillar fragmentation index, SDS-PAGE, and histological structure analysis revealed that the beheading treatment on the shrimp greatly inhibited the dissociation of muscle proteins during frozen storage. Our findings showed that the trypsin in the head of shrimp could be transferred to muscle tissues through the first abdominal segment during long-term storage, thus accelerating the degradation of MPs in the muscle tissues. Therefore, the beheading treatments effectively prolonged the shelf-life of stored shrimp products.
•Alterations in endogenous enzymes in intact and beheaded shrimp were investigated.•Physicochemical properties of muscle proteins decreased with prolonged storage period.•Endogenous enzymes induced damage on MPs during storage.•Beheaded shrimp exhibited stable characteristics than intact samples.•Trypsin might be transferred from head to muscle accelerating degradation of MPs.
Proteinase 3 (PR3), the target antigen of antineutrophil cytoplasm autoantibodies, which are found in patients with Wegener granulomatosis, is a neutrophil serine protease localized within ...cytoplasmic granules. Recently, the human neutrophil antigen NB1 was identified as a specific neutrophil cell surface receptor of PR3. We hypothesized that the unique hydrophobic cluster of PR3 that is not present on human neutrophil elastase and cathepsin G and presumably is also missing in other human PR3 homologs accounts for its binding to the NB1 receptor expressed on the cellular surface of NB1 cells. Instead of generating and testing various artificial human PR3 mutants, we cloned and expressed the very closely related gibbon (Hylobates pileatus) PR3 homolog, which did not bind to the human NB1 receptor. Moreover, a human-gibbon hybrid constructed from the N- and C-terminal half of the human and gibbon PR3, respectively, also did not interact with human NB1. The C-terminal half of gibbon PR3 differs only by 9 residues from human PR3, among which four closely spaced hydrophobic residues are substituted in a nonconservative manner (F166L, W218R, G219A, and L223H). The NB1-bound PR3 was active and was cleared from the surface by α-1-protease inhibitor. Conformational distortion of the hydrophobic 217-225 loop by α-1-protease inhibitor most likely triggers rapid solubilization.
Bone resorption in balance with bone formation is vital for the maintenance of the skeleton and is mediated by osteoclasts.
Cathepsin K is the predominant protease in osteoclasts that degrades the ...bulk of the major bone forming organic component,
type I collagen. Although the potent collagenase activity of cathepsin K is well known, its mechanism of action remains elusive.
Here, we report a cathepsin K-specific complex with chondroitin sulfate, which is essential for the collagenolytic activity
of the enzyme. The complex is an oligomer consisting of five cathepsin K and five chondroitin sulfate molecules. Only the
complex exhibits potent triple helical collagen-degrading activity, whereas monomeric cathepsin K has no collagenase activity.
The primary substrate specificity of cathepsin K is not altered by complex formation, suggesting that the protease-chondroitin
sulfate complex primarily facilitates the destabilization and/or the specific binding of the triple helical collagen structure.
Inhibition of complex formation leads to the loss of collagenolytic activity but does not impair the proteolytic activity
of cathepsin K toward noncollagenous substrates. The physiological relevance of cathepsin K complexes is supported by the
findings that (i) the content of chondroitin sulfate present in bone and accessible to cathepsin K activity is sufficient
for complex formation and (ii) Y212C, a cathepsin K mutant that causes pycnodysostosis (a bone sclerosing disorder) and that
has no collagenase activity but remains potent as a gelatinase, is unable to form complexes. These findings reveal a novel
mechanism of bone collagen degradation and suggest that targeting cathepsin K complex formation would be an effective and
specific treatment for diseases with excessive bone resorption such as osteoporosis.
Cruzain is the major cysteine protease of Trypanosoma cruzi, which is the causative agent of Chagas disease and is a promising target for the development of new chemotherapy. With the goal of ...developing potent nonpeptidic inhibitors of cruzain, the substrate activity screening (SAS) method was used to screen a library of protease substrates initially designed to target the homologous human protease cathepsin S. Structure-based design was next used to further improve substrate cleavage efficiency by introducing additional binding interactions in the S3 pocket of cruzain. The optimized substrates were then converted to inhibitors by the introduction of cysteine protease mechanism-based pharmacophores. Inhibitor 38 was determined to be reversible even though it incorporated the vinyl sulfone pharmacophore that is well documented to give irreversible cruzain inhibition for peptidic inhibitors. The previously unexplored β-chloro vinyl sulfone pharmacophore provided mechanistic insight that led to the development of potent irreversible acyl- and aryl-oxymethyl ketone cruzain inhibitors. For these inhibitors, potency did not solely depend on leaving group pK a, with 2,3,5,6-tetrafluorophenoxymethyl ketone 54 identified as one of the most potent inhibitors with a second-order inactivation constant of 147,000 s−1 M−1. This inhibitor completely eradicated the T. cruzi parasite from mammalian cell cultures and consequently has the potential to lead to new chemotherapeutics for Chagas disease.
Galectin 3 (GAL-3) is a beta galactoside binding lectin that has different roles in normal and pathophysiological conditions. GAL-3 was found to be up regulated in animal models of myocardial ...infarction (MI). Cathepsins are intracellular lysosomal proteases that degrade proteins. The objective of his study is to investigate if high GAL-3 after myocardial infarction has a protective role on the heart through its modulation of lysosomal Cathepsins in ischemic myocardium.
Male C57B6/J mice and GAL-3 knockout (KO) mice were used for permanent ligation of the left anterior descending artery of the heart to create infarction in the anterior myocardium. Hearts and plasma samples were collected 24 hours after the induction of MI and were used for enzyme linked immunosorbent assay and immunofluorescent staining.
Our results show that the significant increase in GAL-3 levels in the left ventricle at 24-hour following MI is associated with significant lower levels of cathepsins B, D, L and S in GAL-3 wild MI group than GAL-3 KO MI group. We also report a significant lower plasma level of Troponin I in GAL-3 wild MI group than GAL-3 KO MI group.
The increased levels of GAL-3 at 24-hour following MI regulates the process of cardiomyocytes injury through modulation of lysosomal cathepsins B, D, L and S.
Donor-specific antibodies (DSA) are a major risk factor for antibody-mediated rejection (ABMR) in solid organ transplantation, and ABMR remains a medical challenge. Therefore, effective anti-ABMR ...therapies are needed to improve overall graft survival. Cathepsin S (Cat S) is an essential protease for antigen peptide loading onto lysosomal/endosomal major histocompatibility complex (MHC) class II molecules to promote antigen presentation. Cat S deficiency produces immuno-deficient phenotypes including a suppressed humoral immune response, and Cat S inhibition reportedly prevents autoimmunity. However, little is known about the effects of Cat S inhibitors on organ transplantation, especially ABMR. Here, we report the pharmacological profile of novel Cat S inhibitors, AS2761325 and AS2863995, and explore their preventive potential on DSA production and acute rejection in a mouse cardiac transplantation model. Cat S inhibitors potently inhibited upregulation of antigen peptide loading MHC class II expression on the surface of splenic B cells and suppressed ovalbumin-induced T cell-dependent antibody production in mice. In a mouse cardiac transplantation model, oral administration of AS2761325 monotherapy inhibited DSA production without affecting graft survival. When combined with a suboptimal dose of tacrolimus, AS2761325 significantly prolonged graft survival. The more potent Cat S inhibitor AS2863995 also prolonged graft survival and almost completely suppressed DSA production. These results suggest that Cat S inhibitors may be promising ABMR prophylaxis drug candidates. Combination therapy comprising a Cat S inhibitor and calcineurin inhibitors may be a more effective immunosuppressive maintenance therapy for controlling both cell-mediated and antibody-mediated rejection.
There is currently no therapeutic drug treatment for traumatic brain injury (TBI) despite decades of experimental clinical trials. This may be because the mechanistic pathways for improving TBI ...outcomes have yet to be identified and exploited. As such, there remains a need to seek out new molecular targets and their drug candidates to find new treatments for TBI. This review presents supporting evidence for cathepsin B, a cysteine protease, as a potentially important drug target for TBI. Cathepsin B expression is greatly up-regulated in TBI animal models, as well as in trauma patients. Importantly, knockout of the cathepsin B gene in TBI mice results in substantial improvements of TBI-caused deficits in behavior, pathology, and biomarkers, as well as improvements in related injury models. During the process of TBI-induced injury, cathepsin B likely escapes the lysosome, its normal subcellular location, into the cytoplasm or extracellular matrix (ECM) where the unleashed proteolytic power causes destruction via necrotic, apoptotic, autophagic, and activated glia-induced cell death, together with ECM breakdown and inflammation. Significantly, chemical inhibitors of cathepsin B are effective for improving deficits in TBI and related injuries including ischemia, cerebral bleeding, cerebral aneurysm, edema, pain, infection, rheumatoid arthritis, epilepsy, Huntington's disease, multiple sclerosis, and Alzheimer's disease. The inhibitor E64d is unique among cathepsin B inhibitors in being the only compound to have demonstrated oral efficacy in a TBI model and prior safe use in man and as such it is an excellent tool compound for preclinical testing and clinical compound development. These data support the conclusion that drug development of cathepsin B inhibitors for TBI treatment should be accelerated.
PDF
