A novel lectin with a distinct Gal_Lectin and CUB domain mediates haemocyte phagocytosis in oyster Crassostrea gigas.

Invertebrate lectins exhibit structural diversity and play crucial roles in the innate immune responses by recognizing and eliminating pathogens. In the present study, a novel lectin containing a Gal_Lectin, a CUB and a transmembrane domain was identified from the Pacific oyster Crassostrea gigas (defined as CgGal-CUB). CgGal-CUB mRNA was detectable in all the examined tissues with the highest expression in adductor muscle (11.00-fold of that in haemocytes, p < 0.05). The expression level of CgGal-CUB mRNA in haemocytes was significantly up-regulated at 3, 24, 48 and 72 h (8.37-fold, 12.13-fold, 4.28-fold and 10.14-fold of that in the control group, respectively) after Vibrio splendidus stimulation. The recombinant CgGal-CUB (rCgGal-CUB) displayed binding capability to Mannan (MAN), peptidoglycan (PGN), D-(+)-Galactose and L-Rhamnose monohydrate, as well as Gram-negative bacteria (Escherichia coli, V. splendidus and Vibrio anguillarum), Gram-positive bacteria (Micrococcus luteus, Staphylococcus aureus, and Bacillus sybtilis) and fungus (Pichia pastoris). rCgGal-CUB was also able to agglutinate V. splendidus, and inhibit V. splendidus growth. Furthermore, rCgGal-CUB exhibited the activities of enhancing the haemocyte phagocytosis towards V. splendidus, and the phagocytosis rate of haemocytes was descended in blockage assay with CgGal-CUB antibody. These results suggested that CgGal-CUB served as a pattern recognition receptor to bind various PAMPs and bacteria, and enhanced the haemocyte phagocytosis towards V. splendidus.

A novel mechanism underlying allosteric regulation of ADAMTS-13 revealed by hydrogen-deuterium exchange plus mass spectrometry.

Background: ADAMTS-13, a plasma metalloprotease, cleaves von Willebrand factor. ADAMTS-13 activity appears to be regulated through allosteric inhibition by its distal C-terminus. Objectives: The objective of this study was to better understand how domain-domain interactions may affect ADAMTS-13 conformations and functions. Methods: We performed deuterium-hydrogen exchange plus mass spectrometry to assess the number and rate of deuterium incorporation into various peptides of full-length ADAMTS-13 and its truncated variants. Results: Under physiological conditions, a bimodal distribution of deuterium incorporation was detected in the peptides from metalloprotease (217-230 and 282-304), cysteine-rich (446-482), and CUB (for complement C1r/C1s, Uegf, Bmp1) domains (1185-1214, 1313-1330, 1341-1347, 1358-1378, and 1393-1407) of full-length recombinant ADAMTS-13, but not of truncated variants. These results suggest that the full-length ADAMTS-13 undergoes conformational changes. On removal of the middle and distal C-terminal domains, the number and rate of deuterium incorporation were increased in the peptides from cysteine-rich (445-467, 467-482, and 495-503) and spacer domains (621-642 and 655-654) but decreased in the peptides from metalloprotease (115-124, 217-230, and 274-281). Moreover, most peptides, except for 217-230 and 1357-1376, exhibited a pD-dependent deuterium incorporation in the full-length ADAMTS-13, but not in the truncated variant (eg, MDTCS or T5C). These results further suggest that the bimodal deuterium incorporation observed in the peptides from the full-length ADAMTS-13 is the result of potential impact from the middle to distal C-terminal domains. Surface plasmon resonance revealed the direct binding interactions between the distal and proximal domains of ADAMTS-13. Conclusion: Our results provide novel insight on how intramolecular interactions may affect conformations of ADAMTS-13, thus regulating its proteolytic functions.

The roles of proteases in prostate cancer.

Since the proposition of the pro-invasive activity of proteolytic enzymes over 70 years ago, several roles for proteases in cancer progression have been established. About half of the 473 active human proteases are expressed in the prostate and many of the most well-characterized members of this enzyme family are regulated by androgens, hormones essential for development of prostate cancer. Most notably, several kallikrein-related peptidases, including KLK3 (prostate-specific antigen, PSA), the most well-known prostate cancer marker, and type II transmembrane serine proteases, such as TMPRSS2 and matriptase, have been extensively studied and found to promote prostate cancer progression. Recent findings also suggest a critical role for proteases in the development of advanced and aggressive castration-resistant prostate cancer (CRPC). Perhaps the most intriguing evidence for this role comes from studies showing that the protease-activated transmembrane proteins, Notch and CDCP1, are associated with the development of CRPC. Here, we review the roles of proteases in prostate cancer, with a special focus on their regulation by androgens.

Distribution and Localization of Mahogunin Ring Finger 1 in the Mouse Central Nervous System.

Mahogunin ring finger 1 (MGRN1), an E3 ubiquitin, is involved in several physiological and neuropathological processes. Although mgrn1 mRNA is widely distributed in the central nervous system (CNS), detailed information on its cellular and subcellular localization is lacking and its physiological role remains unclear. In this study, we aimed to determine the distribution of MGRN1 in the mouse CNS using a newly produced antibody against MGRN1. We found that the MGRN1 protein was expressed in most neuronal cell bodies. An intense MGRN1 expression was also observed in the neuropil of the gray matter in different regions of the CNS, including the main olfactory bulb, cerebral cortex, caudate, putamen, thalamic nuclei, hypothalamic nuclei, medial eminence, superior colliculus, hippocampus, dentate gyrus, and spinal cord. Contrastingly, no MGRN1 expression was observed in glial cells. Double fluorescence and immunoelectron microscopic analyses revealed the intracellular distribution of MGRN1 in pre-synapses and near the outer membrane of the mitochondria in neurons. These findings indicate that MGRN1 is more widely expressed throughout the CNS; additionally, the intracellular expression of MGRN1 suggests that it may play an important role in synaptic and mitochondrial functions.

CDCP1: A promising diagnostic biomarker and therapeutic target for human cancer.

CUB domain-containing protein 1 (CDCP1), as an emerging transmembrane protein, is overexpressed in a variety of malignant tumors including respiratory tumors, digestive system cancers, hematological malignancies and urogenital cancers. Several cancer-related proteins have been reported to interact with CDCP1. It acts as a crucial hub in multiple classical signaling pathways of tumorigenesis and progression. Its overexpression and activation are also associated with prognosis and drug resistance. Due to its important roles in malignant tumors, CDCP1 is expected to be a promising therapeutic target for treatment and a new biomarker for diagnosis. In this article, we review the roles of CDCP1 in diagnosis and management of malignant tumors, and also its regulation in several essential tumor-related pathways.

BMP antagonists in tissue development and disease.

Bone morphogenic proteins (BMPs) are important growth regulators in embryogenesis and postnatal homeostasis. Their tight regulation is crucial for successful embryonic development as well as tissue homeostasis in the adult organism. BMP inhibition by natural extracellular biologic antagonists represents the most intensively studied mechanistic concept of BMP growth factor regulation. It was shown to be critical for numerous developmental programs, including germ layer specification and spatiotemporal gradients required for the establishment of the dorsal-ventral axis and organ formation. The importance of BMP antagonists for extracellular matrix homeostasis is illustrated by the numerous human connective tissue disorders caused by their mutational inactivation. Here, we will focus on the known functional interactions targeting BMP antagonists to the ECM and discuss how these interactions influence BMP antagonist activity. Moreover, we will provide an overview about the current concepts and investigated molecular mechanisms modulating BMP inhibitor function in the context of development and disease.

Expression and functional characterization of the CUB domain-containing protein from the triangle sail mussel (Hyriopsis cumingii) in response to pathogenic infection.

The complement C1r/C1s, Uegf, and Bmp1 (CUB) domains, which are most exclusively found in extracellular and plasma membrane-related proteins, are involved in various biological processes. In this study, a CUB domain-containing protein (designed as HcCDCP) was cloned and characterized from freshwater pearl mussel (Hyriopsis cumingii). The 2280 bp complete cDNA of the HcCDCP contained a 1002 bp open reading frame, which encoded a protein with 333 amino acids. The predicted HcCDCP protein contained a typical CUB domain and a transmembrane region. The tissue distribution analysis indicated that the HcCDCP was detected in all tissues, and the highest expression was found in hepatopancreas followed by gills. After infection with bacteria (i.e., Staphylococcus aureus and Vibrio parahaemolyticus), virus (white spot syndrome virus) and virus analogs (poly[I:C]), the mRNA level of the HcCDCP was significantly upregulated, suggesting that the HcCDCP might be involved in host immune defense response. The RNA interference revealed that the silencing of the HcCDCP could evidently inhibit the expression levels of lysozyme and tumor necrosis factor. Moreover, the recombinant protein of the CUB domain (rCUB) possessed binding capacity to eight different kinds of bacteria. The polysaccharide binding assay showed that the rCUB specifically bound to lipopolysaccharide, peptidoglycan, and D-mannose. This study provided valuable information for exploring the biological roles of CDCPs in the host defense system of mollusks.

Crouching Tiger, Hidden Protein: Searching for Insecticidal Toxins in Venom of the Red Tiger Assassin Bug (Havinthus rufovarius).

Assassin bugs are venomous insects that prey on other arthropods. Their venom has lethal, paralytic, and liquifying effects when injected into prey, but the toxins responsible for these effects are unknown. To identify bioactive assassin bug toxins, venom was harvested from the red tiger assassin bug (Havinthus rufovarius), an Australian species whose venom has not previously been characterised. The venom was fractionated using reversed-phase high-performance liquid chromatography, and four fractions were found to cause paralysis and death when injected into sheep blowflies (Lucilia cuprina). The amino acid sequences of the major proteins in two of these fractions were elucidated by comparing liquid chromatography/tandem mass spectrometry data with a translated venom-gland transcriptome. The most abundant components were identified as a solitary 12.8 kDa CUB (complement C1r/C1s, Uegf, Bmp1) domain protein and a 9.5 kDa cystatin. CUB domains are present in multidomain proteins with diverse functions, including insect proteases. Although solitary CUB domain proteins have been reported to exist in other heteropteran venoms, such as that of the bee killer assassin bug Pristhesancus plagipennis, their function is unknown, and they have not previously been reported as lethal or paralysis-inducing. Cystatins occur in the venoms of spiders and snakes, but again with an unknown function. Reduction and alkylation experiments revealed that the H. rufovarius venom cystatin featured five cysteine residues, one of which featured a free sulfhydryl group. These data suggest that solitary CUB domain proteins and/or cystatins may contribute to the insecticidal activity of assassin bug venom.

Neto proteins regulate gating of the kainate-type glutamate receptor GluK2 through two binding sites.

The neuropilin and tolloid-like (Neto) proteins Neto1 and Neto2 are auxiliary subunits of kainate-type glutamate receptors (KARs) that regulate KAR trafficking and gating. However, how Netos bind and regulate the biophysical functions of KARs remains unclear. Here, we found that the N-terminal domain (NTD) of glutamate receptor ionotropic kainate 2 (GluK2) binds the first complement C1r/C1s-Uegf-BMP (CUB) domain of Neto proteins (i.e. NTD-CUB1 interaction) and that the core of GluK2 (GluK2ΔNTD) binds Netos through domains other than CUB1s (core-Neto interaction). Using electrophysiological analysis in HEK293T cells, we examined the effects of these interactions on GluK2 gating, including deactivation, desensitization, and recovery from desensitization. We found that NTD deletion does not affect GluK2 fast gating kinetics, the desensitization, and the deactivation. We also observed that Neto1 and Neto2 differentially regulate GluK2 fast gating kinetics, which largely rely on the NTD-CUB1 interactions. NTD removal facilitated GluK2 recovery from desensitization, indicating that the NTD stabilizes the GluK2 desensitization state. Co-expression with Neto1 or Neto2 also accelerated GluK2 recovery from desensitization, which fully relied on the NTD-CUB1 interactions. Moreover, we demonstrate that the NTD-CUB1 interaction involves electric attraction between positively charged residues in the GluK2_NTD and negatively charged ones in the CUB1 domains. Neutralization of these charges eliminated the regulatory effects of the NTD-CUB1 interaction on GluK2 gating. We conclude that KARs bind Netos through at least two sites and that the NTD-CUB1 interaction critically regulates Neto-mediated GluK2 gating.

Evidence that cell surface localization of serine protease activity facilitates cleavage of the protease activated receptor CDCP1.

The cellular receptor CUB domain containing protein 1 (CDCP1) is commonly elevated and functionally important in a range of cancers. CDCP1 is cleaved by serine proteases at adjacent sites, arginine 368 (R368) and lysine 369 (K369), which induces cell migration in vitro and metastasis in vivo. We demonstrate that membrane localization of serine protease activity increases efficacy of cleavage of CDCP1, and that both secreted and membrane anchored serine proteases can have distinct preferences for cleaving at CDCP1-R368 and CDCP1-K369. Approaches that disrupt membrane localization of CDCP1 cleaving serine proteases may interfere with the cancer promoting effects of CDCP1 proteolysis.

miR-198 functions as a tumor suppressor in breast cancer by targeting CUB domain-containing protein 1.

The molecular mechanisms underlying the dysregulation of microRNAs (miRs) have been previously documented in breast cancer. miR-198 has been reported to be deregulated in several human cancers. However, the detailed effects of miR-198 on breast cancer progression remain unclear. Using quantitative polymerase chain reaction analysis, we demonstrated in the present study that miR-198 was downregulated in breast cancer tissues and cell lines, and that downregulation of miR-198 was significantly correlated with lymph node metastasis. Functional studies revealed that miR-198 inhibited cell proliferation and migration and promoted cell adhesion in aggressive breast cancer cells in vitro. In addition, we observed that CUB domain-containing protein 1 (CDCP1) was a direct target of miR-198, and that knockdown of CDCP1 inhibited cell proliferation and migration, and promoted cell adhesion, which was similar to the effects of overexpression of miR-198. Taken together, we provide evidence to characterize the role of miR-198/CDCP1 interaction in breast cancer, which may be useful in breast cancer therapy.

[Effect of HIF-2α on regulating CDCP1 to promote hepatocellular carcinoma metastasis].

Objective: To investigate the effect of hypoxia inducible factor 2α (HIF-2α) on regulating CUB domain-containing protein 1 (CDCP1) and its role in hepatocellular carcinoma metastasis. Methods: HIF-2α-knocked down and HIF-2α-stably overexpressing cells (MHCC97H) were prepared by small interfering RNA (siRNA) and lentivirus transfection, respectively. The expression of CDCP1 protein and mRNA in the above cells was detected by western blot and real-time PCR. The effect of HIF-2α on cell invasion ability was determined by Transwell assay. Furthermore, immunohistochemical staining was performed to detect the expression of CDCP1 in human HCC tissue samples. Results: Both HIF-2α and CDCP1 were induced under hypoxic conditions. The activation of CDCP1 under hypoxic conditions was dependent on the expression of HIF-2α.When HIF-2α was overexpressed, the mRNA level of CDCP1 was greatly upregulated (5.92±0.28, P<0.05). When HIF-2α was knocked down by siRNA for 48 h and 72 h, the expression of CDCP1 was significantly downregulated (48 h: 0.25±0.04; 72 h: 0.18±0.02, all P<0.05). Moreover, analysis of human HCC samples showed that CDCP1 expression was correlated with tumor-free survival (P<0.05). Conclusions: The results of this study indicate that the expression of CDCP1 is regulated by HIF-2α and is correlated with the progression of HCC. Inhibition of HIF-2α/CDCP1 may play certain inhibitory role in the metastasis of HCC.

Effect of HIF-2α on regulating CDCP1 to promote hepatocellular carcinoma metastasis / 中华肿瘤杂志

Objective@#To investigate the effect of hypoxia inducible factor 2α (HIF-2α) on regulating CUB domain-containing protein 1 (CDCP1) and its role in hepatocellular carcinoma metastasis.@*Methods@#HIF-2α-knocked down and HIF-2α-stably overexpressing cells (MHCC97H) were prepared by small interfering RNA (siRNA) and lentivirus transfection, respectively. The expression of CDCP1 protein and mRNA in the above cells was detected by western blot and real-time PCR. The effect of HIF-2α on cell invasion ability was determined by Transwell assay. Furthermore, immunohistochemical staining was performed to detect the expression of CDCP1 in human HCC tissue samples.@*Results@#Both HIF-2α and CDCP1 were induced under hypoxic conditions. The activation of CDCP1 under hypoxic conditions was dependent on the expression of HIF-2α.When HIF-2α was overexpressed, the mRNA level of CDCP1 was greatly upregulated (5.92±0.28, P<0.05). When HIF-2α was knocked down by siRNA for 48 h and 72 h, the expression of CDCP1 was significantly downregulated (48 h: 0.25±0.04; 72 h: 0.18±0.02, all P<0.05). Moreover, analysis of human HCC samples showed that CDCP1 expression was correlated with tumor-free survival (P<0.05).@*Conclusions@#The results of this study indicate that the expression of CDCP1 is regulated by HIF-2α and is correlated with the progression of HCC. Inhibition of HIF-2α/CDCP1 may play certain inhibitory role in the metastasis of HCC.

Dysregulated expression of cell surface glycoprotein CDCP1 in prostate cancer.

CUB-domain-containing protein 1 (CDCP1) is a trans-membrane protein regulator of cell adhesion with a potent pro-migratory function in tumors. Given that proteolytic cleavage of the ectodomain correlates with outside-in oncogenic signaling, we characterized glycosylation in the context of cellular processing and expression of CDCP1 in prostate cancer. We detected 135 kDa full-length and proteolytic processed 70 kDa species in a panel of PCa cell models. The relative expression of full-length CDCP1 correlated with the metastatic potential of syngeneic cell models and an increase in surface membrane expression of CDCP1 was observed in tumor compared to adjacent normal prostate tissues. We demonstrated that glycosylation of CDCP1 is a prerequisite for protein stability and plasma membrane localization, and that the expression level and extent of N-glycosylation of CDCP1 correlated with metastatic status. Interestingly, complex N-linked glycans with sialic acid chains were restricted to the N-terminal half of the ectodomain and absent in the truncated species. Characterization of the extracellular expression of CDCP1 identified novel circulating forms and revealed that extracellular vesicles provide additional processing pathways. Employing immunoaffinity mass spectrometry, we detected elevated levels of circulating CDCP1 in patient urine with high-risk disease. Our results establish that differential glycosylation, cell surface presentation and extracellular expression of CDCP1 are hallmarks of PCa progression.

CUB-domain containing protein 1 represses the epithelial phenotype of pancreatic cancer cells.

The prognosis of pancreatic cancer is dismal due to the frequent metastasis and invasion to surrounding organs. Numerous molecules are involved in the malignant behavior of pancreatic cancer cells, but the entire process remains unclear. Several reports have suggested that CUB-domain containing protein-1 (CDCP1) is highly expressed in pancreatic cancer, but its impact on the invasive growth and the upstream regulator remain elusive. To clarify the role of CDCP1 in pancreatic cancer, we here examined the effects of CDCP1 knockdown on the cell behaviors of pancreatic cancer cells. Knockdown of CDCP1 expression in Panc-1 resulted in reduced cellular migration accompanied by the increased expression of E-cadherin and decreased expression of N-cadherin. Knockdown of CDCP1 attenuated the spheroid formation and resistance against gemcitabine, which are some of the cancer stem cell-related phenotypes. Bone morphogenetic protein 4 (BMP4) was found to induce CDCP1 expression via the extracellular signal regulated kinase pathway, suggesting that CDCP1 has a substantial role in the BMP4-induced epithelial-mesenchymal transition. These results indicate that CDCP1 represses the epithelial phenotype of pancreatic cancer cells.