The Emerging Role of Ubiquitin-Specific Protease 36 (USP36) in Cancer and Beyond.

The balance between ubiquitination and deubiquitination is instrumental in the regulation of protein stability and maintenance of cellular homeostasis. The deubiquitinating enzyme, ubiquitin-specific protease 36 (USP36), a member of the USP family, plays a crucial role in this dynamic equilibrium by hydrolyzing and removing ubiquitin chains from target proteins and facilitating their proteasome-dependent degradation. The multifaceted functions of USP36 have been implicated in various disease processes, including cancer, infections, and inflammation, via the modulation of numerous cellular events, including gene transcription regulation, cell cycle regulation, immune responses, signal transduction, tumor growth, and inflammatory processes. The objective of this review is to provide a comprehensive summary of the current state of research on the roles of USP36 in different pathological conditions. By synthesizing the findings from previous studies, we have aimed to increase our understanding of the mechanisms underlying these diseases and identify potential therapeutic targets for their treatment.

The emerging role of deubiquitylating enzyme USP21 as a potential therapeutic target in cancer.

Although certain members of the Ubiquitin-specific peptidases (USPs) have been recognized as promising therapeutic targets for various diseases, research progress regarding USP21 has been relatively sluggish in its early stages. USP21 is a crucial member of the USPs subfamily, involved in diverse cellular processes such as apoptosis, DNA repair, and signal transduction. Research findings from the past decade demonstrate that USP21 mediates the deubiquitination of multiple well-known target proteins associated with critical cellular processes relevant to both disease and homeostasis, particularly in various cancers.This reviewcomprehensively summarizes the structure and biological functions of USP21 with an emphasis on its role in tumorigenesis, and elucidates the advances on the discovery of tens of small-molecule inhibitors targeting USP21, which suggests that targeting USP21 may represent a potential strategy for cancer therapy.

Curriculum vitae of CUG binding protein 1 (CELF1) in homeostasis and diseases: a systematic review.

RNA-binding proteins (RBPs) are kinds of proteins with either singular or multiple RNA-binding domains (RBDs), and they can assembly into ribonucleic acid-protein complexes, which mediate transportation, editing, splicing, stabilization, translational efficiency, or epigenetic modifications of their binding RNA partners, and thereby modulate various physiological and pathological processes. CUG-BP, Elav-like family 1 (CELF1) is a member of the CELF family of RBPs with high affinity to the GU-rich elements in mRNA, and thus exerting control over critical processes including mRNA splicing, translation, and decay. Mounting studies support that CELF1 is correlated with occurrence, genesis and development and represents a potential therapeutical target for these malignant diseases. Herein, we present the structure and function of CELF1, outline its role and regulatory mechanisms in varieties of homeostasis and diseases, summarize the identified CELF1 regulators and their structure-activity relationships, and prospect the current challenges and their solutions during studies on CELF1 functions and corresponding drug discovery, which will facilitate the establishment of a targeted regulatory network for CELF1 in diseases and advance CELF1 as a potential drug target for disease therapy.

Lysine-specific demethylase 7A (KDM7A): A potential target for disease therapy.

Histone demethylation is a kind of epigenetic modification mediated by a variety of enzymes and participates in regulating multiple physiological and pathological events. Lysine-specific demethylase 7A is a kind of α-ketoglutarate- and Fe(II)-dependent demethylase belonging to the PHF2/8 subfamily of the JmjC demethylases. KDM7A is mainly localized in the nucleus and contributes to transcriptional activation via removing mono- and di-methyl groups from the lysine residues 9 and 27 of Histone H3. Mounting studies support that KDM7A is not only necessary for normal embryonic, neural, and skeletal development, but also associated with cancer, inflammation, osteoporosis, and other diseases. Herein, the structure of KDM7A is described by comparing the similarities and differences of its amino acid sequences of KDM7A and other Histone demethylases; the functions of KDM7A in homeostasis and dyshomeostasis are summarized via documenting its content and related signaling; the currently known KDM7A-specific inhibitors and their structural relationship are listed based on their structure optimization and pharmacological activities; and the challenges and opportunities in exploring functions and developing targeted agents of KDM7A are also prospected via presenting encountered problems and potential solutions, which will provide an insight in functional exploration and drug discovery for KDM7A-related diseases.

Antimicrobial peptide hepcidin contributes to restoration of the intestinal flora after Aeromonas hydrophila infection in Acrossocheilus fasciatus.

Hepcidin is a cysteine-rich antimicrobial peptide that serves an important role in the immunity system of fishes. It exhibits antibacterial, antifungal, antiviral, and antitumor activities. However, the exact role of fish hepcidin in the regulation of the intestinal flora still remains a mystery. In our study, we sequenced and characterized hepcidin from the liver of Acrossocheilus fasciatus. Phylogenetic tree analysis showed that A. fasciatus hepcidin and Gobiocypris rarus hepcidin were the most closely related, and both belonged to the fish HAMP1 cluster. Studies conducted on in vivo tissue distribution showed that the expression of hepcidin was highest in healthy A. fasciatus liver. Aeromonas hydrophila infection was confirmed by the increased expression of pro-inflammatory cytokine genes and bacterial loads in A. fasciatus tissues. After A. hydrophila infection, hepcidin expression significantly increased in the liver, spleen, and head kidney. In vitro antibacterial assays showed that hepcidin exhibits strong broad spectrum antibacterial activity. Furthermore, we examined the regulatory effect of hepcidin on the intestinal flora and found that A. fasciatus hepcidin restored the reduced diversity and compositional changes in intestinal flora caused by A. hydrophila infection. Our results suggest that hepcidin could regulate the intestinal flora in fishes; however, the underlying mechanisms need to be explored in greater detail.

Barbel steed (Hemibarbus labeo) NK-lysin protects against Aeromonas hydrophila infection via immunomodulatory activity.

NK-lysins (NKLs) are a family of multifunctional antimicrobial peptides that have activity against various microorganisms. However, the immunomodulatory activity of NKL in fish remains unclear. In this study, the cDNA sequence of barbel steed (Hemibarbus labeo) NKL gene was cloned. Barbel steed NKL amino acid sequence comprised a signal peptide and a mature peptide. The saposin B domain in the mature peptide has six conserved cysteines that form three disulfide bonds. Phylogenetic analysis showed that the barbel steed NKL was most closely related to that of the common carp (Cyprinus carpio) NKL. Differential expression analysis showed that the barbel steed NKL gene was expressed in all tested tissues, with the highest expression in the spleen. In response to Aeromonas hydrophila infection, NKL was significantly upregulated in the liver, spleen, head kidney, and gill. The barbel steed NKL showed strong antibacterial activity against Vibrio parahaemolyticus, V. alginolyticus, V. vulnificus, and Listeria monocytogenes. However, NKL had no antibacterial activity against the pathogenic bacteria A. hydrophila. Lactate dehydrogenase release assays showed that NKL damaged the V. parahaemolyticus cell membrane. NKL significantly increased barbel steed survival rate after A. hydrophila infection and upregulated IL-1ß and TNF-α expression in the spleen and head kidney. NKL induced monocyte/macrophage chemotaxis and enhanced the respiratory burst and proinflammatory cytokine expression. Our study shows that fish NKL exhibits immunomodulatory effects and protects the host from pathogenic infections independent of direct bacterial clearance.

Sequence analysis of hepcidin in barbel steed (Hemibarbus labeo): QSHLS motif confers hepcidin iron-regulatory activity but limits its antibacterial activity.

Fish hepcidin genes are generally classified into two groups: hamp1-and hamp2-type isoforms. Hamp1-type hepcidin exhibits iron regulatory and antimicrobial activity, while hamp2-type shows a unique role in the immune response against various pathogens. An iron-regulatory motif exists at the N-terminus of hamp1-type hepcidin; however, the functional effect of this motif in fish is not well understood. Here, cDNA of the barbel steed (Hemibarbus labeo) hepcidin gene was cloned and sequenced. The predicted amino acid sequence comprised a signal peptide, a prodomain, and a mature peptide. Phylogenetic tree analysis revealed that barbel steed hepcidin belongs to the fish HAMP1 cluster and is closely related to Chinese rare minnow (Gobiocypris rarus) hepcidin. Barbel steed hepcidin is constitutively expressed in healthy fish tissues, predominantly in the liver. Following iron dextran treatment or Aeromonas hydrophila infection, expression of barbel steed hepcidin increased significantly in tested tissues. In vivo administration of intact hepcidin mature peptide (hep25) significantly and dose-dependently reduced ferroportin 1 expression, while truncated hepcidin mature peptide (hep20) lacking a QSHLS motif had no such effect. In vitro treatment of barbel steed monocytes/macrophages with hep25, but not hep20, increased the labile iron pool levels. Hep25 and hep20 conferred antibacterial activity only against A. hydrophila and Vibrio vulnificus, with greater activity of the latter at low concentrations. Neither hep25 nor hep20 impaired the cell membrane integrity of A. hydrophila, but could hydrolyze its genomic DNA; lack of a QSHLS motif enables hep20 to have a better hydrolytic effect. In summary, we identified an iron-regulatory motif in a fish species and demonstrated that this motif confers hamp1-type hepcidin iron-regulatory activity, but attenuates its antibacterial activity.

Differential contribution of protein phosphatase 1α to cell transformation of different cell types.

Protein phosphorylation plays roles in cell transformation. Numerous protein kinase enzymes actively participate in the formation of various types of cancer by phosphorylating downstream substrates. Aurora­A is a widely known Serine/Threonine (Ser/Thr) oncogenic kinase, which is upregulated in more than twenty types of human cancer. This enzyme phosphorylates a wide range of substrates. For example, Aurora­A induces cell transformation by phosphorylating hepatoma upregulated protein (HURP) at four serine residues, which in turn decreases the phosphorylated levels of cell­growth suppressive Jun N­terminal kinase (p­JNK). Various protein phosphatase enzymes are considered tumor suppressors by the dephosphorylation and consequent inactivation of their oncogenic substrates. Protein phosphatase 1α (PP1α), for instance, acts on Aurora­A by dephosphorylating its substrates. However, the role of PP1α in cancer progression remains ambiguous. PP1α is overexpressed in several cancer tissues, and induces cell apoptosis and differentiation or it inhibits tumor formation in other types of cells. In addition, positive and negative correlations between PP1α expression and lung cancer development have been documented. These observations suggest the differential regulation of PP1α in various cancer tissues, or propose an ambiguous contribution of PP1α to lung cancer development. In order to investigate these contradictory conclusions, it was reported that the chromosomal region covering the PP1α locus was subjected to DNA alterations, such as gain or loss in various human cancer types by a study based on literature search. Upregulation of PP1α was noted in a collection of lung cancer tissues, and was required for the cell transformation of the lung cancer cell line A549. In contrast to this finding, overexpression of ectopic PP1α inhibited cell proliferation in 293T cells. Mechanistic studies revealed that PP1α activated AKT in A549 cells, whereas it further inactivated AKT and disrupted the HURP/JNK signaling cascade in 293T cells. Collectively, the data indicated that PP1α exerted an oncogenic function in lung cancer, while exhibiting various effects on cell transformation in different types of cells via distinct or opposite mechanisms.

Effect of oridonin-mediated hallmark changes on inflammatory pathways in human pancreatic cancer (BxPC-3) cells.

AIM: To investigate the effect of oridonin on nuclear transcription factors and to study the relationship between biological behavior and inflammatory factors in human pancreatic cancer (BxPC-3) cells. METHODS: BxPC-3 cells were treated with various concentrations of oridonin, and viability curves were generated to test for inhibitory effects of the drug on cells. The expression of cytokines such as interleukin-1ß (IL-1ß), IL-6, or IL-33 was detected in BxPC-3 cell supernatants using an enzyme-linked immunosorbent assay (ELISA), and the protein expression of nuclear transcription factors including nuclear factor κB, activating protein-1, signal transducer and activator of transcription 3, bone morphogenetic protein 2, transforming growth factor ß1 and sma and mad homologues in BxPC-3 cells was detected using Western blot. Carcinoma hallmark-related proteins such as survivin, vascular endothelial growth factor, and matrix metallopeptidase 2 were also detected using immunoblotting, and intra-nuclear IL-33 expression was detected using immunofluorescent staining. RESULTS: Treatment with oridonin reduced the viability of BxPC-3 cells in a dose dependent manner. The cells exhibited reduced growth following treatment with 8 µg/mL oridonin (13.05% ± 3.21%, P < 0.01), and the highest inhibitory ratio was 90.64% ± 0.70%, which was achieved with oridonin at a dose of 32 µg/mL. The IC50 value of oridonin in BxPC-3 cells was 19.32 µg/mL. ELISA analysis revealed that oridonin down-regulated the inflammatory factors IL-1ß, IL-6, and IL-33 in a dose-dependent manner. IL-1ß expression was significantly reduced in the 16 and 32 µg/mL treatment groups compared to the control group (12.97 ± 0.45 pg/mL, 11.17 ± 0.63 pg/mL vs 14.40 ± 0.38 pg/mL, P < 0.01). Similar trends were observed for IL-6 expression, which was significantly reduced in the 16 and 32 µg/mL treatment groups compared to the control group (4.05 ± 0.14 pg/mL vs 4.45 ± 0.43 pg/mL, P < 0.05; 3.95 ± 0.13 pg/mL vs 4.45 ± 0.43 pg/mL, P < 0.01). IL-33 expression was significantly reduced in the 8, 16, and 32 µg/mL treatment groups compared to the control group (911.05 ± 14.18 pg/mL vs 945.25 ± 12.09 pg/mL, P < 0.05; 802.70 ± 11.88 pg/mL, 768.54 ± 10.98 pg/mL vs 945.25 ± 12.09 pg/mL, P < 0.01). Western blot and immunofluorescent staining analyses suggested that oridonin changed the hallmarks and regulated the expression of various nuclear transcription factors. CONCLUSION: The results obtained suggest that oridonin alters the hallmarks of pancreatic cancer cells through the regulation of nuclear transcription factors.