Proteolytic processing of ErbB4 in breast cancer

ErbB4 is a receptor tyrosine kinase that can signal by a mechanism involving proteolytic release of intracellular and extracellular receptor fragments. Proteolysis-dependent signaling of ErbB4 has been proposed to be enhanced in breast cancer, mainly based on immunohistochemical localization of intracellular epitopes in the nuclei. To more directly address the processing of ErbB4 in vivo, an ELISA was developed to quantify cleaved ErbB4 ectodomain from serum samples. Analysis of 238 breast cancer patients demonstrated elevated quantities of ErbB4 ectodomain in the serum (≥ 40 ng/mL) in 21% of the patients, as compared to 0% of 30 healthy controls (P = 0.002). Significantly, the elevated serum ectodomain concentration did not correlate with the presence of nuclear ErbB4 immunoreactivity in matched breast cancer tissue samples. However, elevated serum ectodomain concentration was associated with the premenopausal status at diagnosis (P = 0.04), and estradiol enhanced ErbB4 cleavage in vitro. A 3.4 ? X-ray crystal structure of a complex of ErbB4 ectodomain and the Fab fragment of anti-ErbB4 mAb 1479 localized the binding site of mAb 1479 on ErbB4 to a region on subdomain IV encompassing the residues necessary for ErbB4 cleavage. mAb 1479 also significantly blocked ErbB4 cleavage in breast cancer cell xenografts in vivo, and the inhibition of cleavage was associated with suppression of xenograft growth. These data indicate that ErbB4 processing is enhanced in breast cancer tissue in vivo, and that ErbB4 cleavage can be stimulated by estradiol and targeted with mAb 1479.     

Ubiquitin networks in cancer

Conjugation of ubiquitin to cellular proteins has emerged as a post-translational modification, which affects major cellular processes, including cell cycle, proliferation and apoptosis. The ubiquitin-mediated signaling is frequently altered in cancer cells, with several tumor suppressors and oncogenes representing enzymes of the ubiquitin conjugation and deconjugation pathways. Recently, ubiquitination has been involved into selective degradation of both proteins and mitochondria by autophagy. Studying this novel role of ubiquitin can shed light on autophagy as a tumor suppressor mechanism as well as provide insights into the role of autophagy in survival of tumor cells, thus aiding the design of better cancer therapies.     

Proteolytic modification of swelling-activated Cl- current in LNCaP prostate cancer epithelial cells

The effects of intracellular application of trypsin on the Cl^– current induced by hypotonic cell swelling (I _Cl,swell) in human prostate cancer epithelial cells (LNCaP) was studied using the patch-clamp technique. In cells predialyzed with 1 mg/mL trypsin, I _Cl,swell developed and diminished in response to the application and withdrawal of hypotonic solution about three times faster than that in control cells. In trypsin-infused cells, I _Cl,swell also had about twofold higher current density and displayed considerably slowed voltage-dependent inactivation, which was quite pronounced in control cells at potentials above +60 mV. Trypsin-induced modification of I _Cl,swell could be prevented by coinfusion of 10 mg/mL soybean trypsin inhibitor, suggesting that proteolytic cleavage of essential intracellular structural domains of the I _Cl,swell-carrying volume-regulated anion channel (VRAC) was responsible for this functional modification. The effect of trypsin was not dependent on the presence of intracellular ATP. We conclude that VRACs, similarly to voltage-gated Na⁺, K⁺, and Cl^– channels, possess intracellular inactivation domain(s) subjected to proteolytic cleavage that may function in conformity with the classical ball-and-chain inactivation model.     

Cell communication networks in cancer invasion

The invasion of cancer is a major clinical problem. It is now apparent that invasion is not a simply a cancer cell autonomous process but relies on a complex network of paracrine interactions. Furthermore, this network can change as cancer cells disseminate. Here we summarise the key components of the network and their mechanisms of communication. Finally, we discuss the difficulties and opportunities that this complex network of interactions presents during cancer therapy.     

MicroRNA-modulated autophagic signaling networks in cancer

MicroRNAs (miRNAs) are small, non-coding endogenous RNAs ～22 nucleotides (nt) in length that may play the essential roles for regulation of programed cell death, referring to apoptosis and autophagy. Of note, autophagy is an evolutionarily conserved, multi-step lysosomal degradation process in which a cell degrades long-lived proteins and damaged organelles. Accumulating evidence has recently revealed that miRNAs can modulate the autophagic pathways in many pathological processes, most notably cancer. In this review, we focus on highlighting the dual functions of miRNAs as either oncogenes (e.g., miRNA-183, miRNA-376b, miRNA-106a, miRNA-221/222, miRNA-31 and miRNA-34c) or tumor suppressors (e.g., miRNA-30a, miRNA-101 and miRNA-9*) via mediating several autophagic signaling pathways in cancer pathogenesis. Taken together, these findings may uncover the regulatory mechanisms of oncogenic and tumor suppressive miRNAs in autophagy, which would provide a better understanding of miRNA-modulated autophagic signaling networks for future cancer therapeutics.     

Protein kinase signaling networks in cancer

Protein kinases orchestrate the activation of signaling cascades in response to extracellular and intracellular stimuli to control cell growth, proliferation, and survival. The complexity of numerous intracellular signaling pathways is highlighted by the number of kinases encoded by the human genome (539) and the plethora of phosphorylation sites identified in phosphoproteomic studies. Perturbation of these signaling networks by mutations or abnormal protein expression underlies the cause of many diseases including cancer. Recent RNAi screens and cancer genomic sequencing studies have revealed that many more kinases than anticipated contribute to tumorigenesis and are potential targets for inhibitor drug development intervention. This review will highlight recent insights into known pathways essential for tumorigenesis and discuss exciting new pathways for therapeutic intervention.     

Proteolytic changes in plasma fibrinogen from ovarian venous blood in patients with cervix cancer

From 9 female patients suffering from carcinoma cervicis (8 women with a stage Ib, 1 woman with a stage IIa carcinoma) blood was taken immediately from the ovarian veins and a cubital vein after laparotomy on the occasion of a surgical intervention according to Wertheim-Held. Fibrinogen was isolated from plasmas by affinity chromatography at fibrin monomer Sepharose and characterized by SDS-PAGE. With one exception proteolytically changed fibrinogens could be demonstrated in all plasmas. In 7 cases the fibrinogens from ovarian blood were more degraded than fibrinogen derivates in the blood obtained from cubital veins. It is assumed that the proteinase and/or plasminogen activator activities of tumor tissues are of importance for the observed proteolytic effects.     

Regulation patterns in signaling networks of cancer

Background  

Formation of cellular malignancy results from the disruption of fine tuned signaling homeostasis for proliferation, accompanied by mal-functional signals for differentiation, cell cycle and apoptosis. We wanted to observe central signaling characteristics on a global view of malignant cells which have evolved to selfishness and independence in comparison to their non-malignant counterparts that fulfill well defined tasks in their sample.     

Integrated gene networks in breast cancer development

Breast cancer is a complex and heterogenous disease. Classical molecular medical approaches cannot fully understand and comprehend its pathogenesis. In this review, the development of new biological markers for the early detection and creation of guided and specific therapy of breast cancer are discussed in light of the rapid advances in the “omics”. Results of cancer research in combination with large-scale methods that examine the expression status of genes and proteins have identified a large number of new biomarkers as well as confirmed the human growth hormone as an important player in the pathogenesis of this disease through its autocrine regulation where it influences the activation of Pax5 and HOXA1 gene networks.     

Signalling networks that cause cancer

Cancer is caused by the stepwise accumulation of mutations that affect growth control, differentiation and survival. The view that mutations affect discrete signalling pathways, each contributing to a specific aspect of the full malignant phenotype, has proved to be too simplistic. We now know that oncogenes and tumour suppressors depend on one another for their selective advantage, and that they affect multiple pathways that intersect and overlap. The interactive nature of each genetic change has important implications for cancer therapy and for the stepwise model of carcinogenesis.     

Signalling networks that cause cancer

Cancer is caused by the stepwise accumulation of mutations that affect growth control, differentiation and survival. The view that mutations affect discrete signalling pathways, each contributing to a specific aspect of the full malignant phenotype, has proved to be too simplistic. We now know that oncogenes and tumour suppressors depend on one another for their selective advantage, and that they affect multiple pathways that intersect and overlap. The interactive nature of each genetic change has important implications for cancer therapy and for the stepwise model of carcinogenesis.     

Proteolytic events in cryonecrotic cell death: Proteolytic activation of endonuclease P23

Although cryosurgery is attaining increasing clinical acceptance, our understanding of the mechanisms of cryogenic cell destruction remains incomplete. While it is generally accepted that cryoinjured cells die by necrosis, the involvement of apoptosis was recently shown. Our studies of liver cell death by cryogenic temperature revealed the activation of endonuclease p23 and its de novo association with the nuclear matrix. This finding is strongly suggestive of a programmed-type of cell death process. The presumed order underlying cryonecrotic cell death is addressed here by examining the mechanism of p23 activation. To that end, nuclear proteins that were prepared from fresh liver, which is devoid of p23 activity, were incubated with protein fractions isolated from liver exposed to freezing/thawing that possessed a presumed p23 activation factor. We observed that the activation of p23 was the result of a proteolytic event in which cathepsin D played a major role. Different patterns of proteolytic cleavage of nuclear proteins after in vitro incubation of nuclei and in samples isolated from frozen/thawed liver were observed. Although both processes induced p23 activation, the incubation experiments generated proteolytic hallmarks of apoptosis, while freezing/thawing of whole liver resulted in typical necrotic PARP-1 cleavage products and intact lamin B. As an explanation we offer a hypothesis that after freezing, cells possess the potential to die through necrotic as well as apoptotic mechanisms, based on our finding that the cytosol of cells exposed to cryogenic temperatures contains both necrotic and apoptotic executors of cell death.     

Fungal Proteolytic Enzymes

Two kinds of proteolytic enzyme, tentatively named acid protease A and B which showed a single peak on electrophoresis individually, were isolated from the crude enzyme powder obtained from the broth filtrate cultured with Asper gillus niger var. macrosporus. Acid protease B is similar too the fungal acid protease previously reported, bccause the enzyme exhibits optimum activity on milk casein at about pH 2.6 and 55°C when the incubation was done at pH 2.6. Acid protease A is a new proteolytic enzyme, because the enzyme exhibits optimum activity on milk casein at about 2.0 and 70°C or 60°C when the incubation was done at pH 2.6 or 1.5 respectively.     

Proteolytic enzymes in peptide synthesis

Summary In this paper, the literature of the past few years on the application of the proteolytic enzymes in peptide synthesis is summarized.The principle is sound and peptide synthesis for commercial purposes appears feasible. The exclusion of water or its use at a low concentration in immiscible or in biphasic media ensures controlled hydrolysis. The use of proteolytic enzymes attached to a solid support has proved a convenient method of synthesis. Synthesis of peptides with some enzymes occurs by bond exchange but with others the enzymes can extract a water molecule from a free carboxy and an unprotected group so as to create an amide bond.Abbreviations Ac acetyl - BOC t-butyloxycarbony - But butyl - Bz benzoyl - Bzl benzyl - Et ethyl - Hyac -hydroxyacetic acid - Hypp -hydroxypropionic acid - Me methyl - PMZ p-methoxybenzoyloxycarbonyl - Z benzyloxycarbonyl     

Proteolytic activities in Bacillus.

Major advances have been made in understanding the regulation of expression of Bacillus subtilis protease genes. A phosphorelay mechanism as well as a two-component regulatory system allow conditions of the growth medium to be transmitted to the gene level resulting in expression of extracellular protease genes.     

Natural agents mediated autophagic signal networks in cancer

Recent studies suggested that natural compounds are important in finding targets for cancer treatments. Autophagy (“self-eating”) plays important roles in multiple diseases and acts as a tumor suppressor in cancer. Here, we examined the molecular mechanism by which natural agents regulate autophagic signals. Understanding the relationship between natural agents and cellular autophagy may provide more information for cancer diagnosis and chemoprevention.