Phileucin - A Cyclic Dipeptide Similar to Phevalin (Aureusimine B) from Streptomyces coelicolor M1146

Overexpression of a putative type III polyketide synthase (PKSIII) from the marine myxobacterium Enhygromyxa salina SWB007 in Streptoinyces coelicolor MI 146 led to the accumulation of a novel monoketopiperazine consisting of phenylalanine and isoleucine. This compound was named phileucin and shows high structural similarity to phevalin (aureusimine B). The protease inhibiting activity was tested against human cathepsin L, human leukocyte elastase; bovine trypsin and bovine chymotrypsin. In contrast to phevalin, no protease inhibition was observed.

Muscadine grape skin extract can antagonize Snail-cathepsin L-mediated invasion, migration and osteoclastogenesis in prostate and breast cancer cells

To develop new and effective chemopreventive agents against bone metastasis, we assessed the effects of muscadine grape skin extract (MSKE), whose main bioactive component is anthocyanin, on bone turnover, using prostate and breast cancer cell models overexpressing Snail transcription factor. MSKE has been shown previously to promote apoptosis in prostate cancer cells without affecting normal prostate epithelial cells. Snail is overexpressed in prostate and breast cancer, and is associated with increased invasion, migration and bone turnover/osteoclastogenesis. Cathepsin L (CatL) is a cysteine cathepsin protease that is overexpressed in cancer and involved in bone turnover. Snail overexpression in prostate (LNCaP, ARCaP-E) and breast (MCF-7) cancer cells led to increased CatL expression/activity and phosphorylated STAT-3 (pSTAT-3), compared to Neo vector controls, while the reverse was observed in C4-2 (the aggressive subline of LNCaP) cells with Snail knockdown. Moreover, CatL expression was higher in prostate and breast tumor tissue compared to normal tissue. MSKE decreased Snail and pSTAT3 expression, and abrogated Snail-mediated CatL activity, migration and invasion. Additionally, Snail overexpression promoted osteoclastogenesis, which was significantly inhibited by the MSKE as effectively as Z-FY-CHO, a CatL-specific inhibitor, or osteoprotegerin, a receptor activator of nuclear factor kappa B ligand (RANKL) antagonist. Overall, these novel findings suggest that Snail regulation of CatL may occur via STAT-3 signaling and can be antagonized by MSKE, leading to decreased cell invasion, migration and bone turnover. Therefore, inhibition using a natural product such as MSKE could potentially be a promising bioactive compound for bone metastatic cancer.

Diet-derived advanced glycation end products or lipofuscin disrupts proteostasis and reduces life span in Drosophila melanogaster

Advanced glycation end product (AGE)-modified proteins are formed by the nonenzymatic glycation of free amino groups of proteins and, along with lipofuscin (a highly oxidized aggregate of covalently cross-linked proteins, sugars, and lipids), have been found to accumulate during aging and in several age-related diseases. As the in vivo effects of diet-derived AGEs or lipofuscin remain elusive, we sought to study the impact of oral administration of glucose-, fructose-, or ribose-modified albumin or of artificial lipofuscin in a genetically tractable model organism. We report herein that continuous feeding of young Drosophila flies with culture medium enriched in AGEs or in lipofuscin resulted in reduced locomotor performance and in accelerated rates of AGE-modified proteins and carbonylated proteins accumulation in the somatic tissues and hemolymph of flies, as well as in a significant reduction of flies health span and life span. These phenotypic effects were accompanied by reduced proteasome peptidase activities in both the hemolymph and the somatic tissues of flies and higher levels of oxidative stress; furthermore, oral administration of AGEs or lipofuscin in flies triggered an upregulation of the lysosomal cathepsin B, L activities. Finally, RNAi-mediated cathepsin D knockdown reduced flies longevity and significantly augmented the deleterious effects of AGEs and lipofuscin, indicating that lysosomal cathepsins reduce the toxicity of diet-derived AGEs or lipofuscin. Our in vivo studies demonstrate that chronic ingestion of AGEs or lipofuscin disrupts proteostasis and accelerates the functional decline that occurs with normal aging.

Thymocyte selection regulates the homeostasis of IL-7-expressing thymic cortical epithelial cells in vivo

Thymic epithelial cells (TECs) help orchestrate thymopoiesis, and TEC differentiation relies on bidirectional interactions with thymocytes. Although the molecular mediators that stimulate medullary thymic epithelial cell (mTEC) maturation are partially elucidated, the signals that regulate cortical thymic epithelial cell (cTEC) homeostasis remain elusive. Using IL-7 reporter mice, we show that TECs coexpressing high levels of IL-7 (Il7(YFP+) TECs) reside within a subset of CD205(+)Ly51(+)CD40(low) cTECs that coexpresses Dll4, Ccl25, Ccrl1, Ctsl, Psmb11, and Prss16 and segregates from CD80(+)CD40(high) mTECs expressing Tnfrsf11a, Ctss, and Aire. As the frequency of Il7(YFP+) TECs gradually declines as mTEC development unfolds, we explored the relationship between Il7(YFP+) TECs and mTECs. In thymic organotypic cultures, the thymocyte-induced reduction in Il7(YFP+) TECs dissociates from the receptor activator of NF-κB-mediated differentiation of CD80(+) mTECs. Still, Il7(YFP+) TECs can generate some CD80(+) mTECs in a stepwise differentiation process via YFP(-)Ly51(low)CD80(low) intermediates. Il7(YFP+) TECs are sustained in Rag2(-/-) mice, even following in vivo anti-CD3ε treatment that mimics the process of pre-TCR β-selection of thymocytes to the double positive (DP) stage. Using Marilyn-Rag2(-/-) TCR transgenic, we find that positive selection into the CD4 lineage moderately reduces the frequency of Il7(YFP+) TECs, whereas negative selection provokes a striking loss of Il7(YFP+) TECs. These results imply that the strength of MHC/peptide-TCR interactions between TECs and thymocytes during selection constitutes a novel rheostat that controls the maintenance of IL-7-expressing cTECs.

Cathepsin B, D, and L regulation in cyclosporin A-mediated gingival hyperplasia of a patient with sarcoidosis

BACKGROUND

Cyclosporin A (CsA) is an immunosuppressant with side effects including gingival hyperplasia. Sarcoidosis is a systemic disease characterized by granulomas. Here, we report on a rare case of sarcoidosis with gingival hyperplasia to clarify whether clinical observation corresponds to in vitro results.

METHODS

Gingival fibroblasts (HGFs) were isolated from healthy gingiva and cultured with CsA. Total RNA was collected and expression of mRNAs examined using semi-quantitative RT-PCR analysis. Cathepsin B, D, and L expression in overgrown gingiva of the patient was examined by immunohistochemistry.

RESULTS

Cathepsin D, L, and vascular endothelial growth factor (VEGF)165 mRNA were markedly suppressed in CsA-treated HGFs, whereas cathepsin B, matrix metalloproteinase-1 (MMP-1) and tissue inhibitor of metalloproteinase-1 (TIMP-1) mRNA were not reduced. Next, the decrease of cathepsin B and L expression in enlarged gingiva was observed, whereas an increase of cathepsin D expression was observed. Clinically, the enlarged gingival lesions were fully resolved by performing oral infection control.

CONCLUSIONS

Cathepsins regulation might be an important factor in the development of CsA-mediated gingival hyperplasia.

Molecular cloning, characterization, expression and activity analysis of cathepsin L in Chinese mitten crab, Eriocheir sinensis

Cathepsins, a superfamily of hydrolytic enzymes produced and enclosed within lysosomes, function in immune response in vertebrates; however, their function within the innate immune system of invertebrates remains largely unknown. Therefore, we investigated the immune functionality of cathepsin L (catL) in Chinese mitten crab (Eriocheir sinensis), a commercially important and disease vulnerable aquaculture species. The full-length catL cDNA (1274 bp) was cloned via PCR based upon an initial expressed sequence tag (EST) isolated from a hepatopancreatic cDNA library. The catL cDNA contained a 978 bp open reading frame (ORF) that encoded a putative 325 amino acid (aa) protein. Comparisons with other reported invertebrate and vertebrate sequences revealed conserved gene structure and enzyme active sites common among papain-like cysteine proteases, and high percent identity among other invertebrate cathepsins. CatL mRNA expression in E. sinensis was (a) tissue-specific, with the highest expression observed in hepatotpancreas, gill, stomach, and hemocytes, and (b) responsive in hemocytes to a Vibrio anguillarum challenge, the catL expression level and enzyme activity both with peak exposure observed 8 h post-injection. Collectively, data demonstrate the successful isolation of catL from the Chinese mitten crab, and its involvement in the innate immune system of an invertebrate.