Serine proteases are involved in many processes in the nervous system and specific inhibitors tightly control their proteolytic activity. Thrombin is thought to play a role in tissue development and homeostasis. To date, protease nexin-1 is the only known endogenous protease inhibitor that specifically interferes with thrombotic activity and is expressed in the brain. In this study, we report the detection of a novel thrombin inhibitory activity in the brain of protease nexin-1 (؊/؊) mice. Purification and subsequent analysis by tandem mass spectrometry identified this protein as the phosphatidylethanolamine-binding protein (PEBP). We demonstrate that PEBP exerts inhibitory activity against several serine proteases including thrombin, neuropsin, and chymotrypsin, whereas trypsin, tissue type plasminogen activator, and elastase are not affected. Since PEBP does not share significant homology with other serine protease inhibitors, our results define it as the prototype of a novel class of serine protease inhibitors. PEBP immunoreactivity is found on the surface of Rat-1 fibroblast cells and although its sequence contains no secretion signal, PEBP-H 6 can be purified from the conditioned medium upon recombinant expression.

Cyclin-dependent kinases (CDKs) are proteins pivotal to a wide range of cellular functions, most importantly cell division and transcription, and their dysregulations have been implicated as prominent drivers of tumorigenesis. Besides the well-established role of cell cycle CDKs in cancer, the involvement of transcriptional CDKs has been confirmed more recently. Most cancers overtly employ CDKs that serve as key regulators of transcription (e.g., CDK9) for a continuous production of short-lived gene products that maintain their survival. As such, dysregulation of the CDK9 pathway has been observed in various hematological and solid malignancies, making it a valuable anticancer target. This therapeutic potential has been utilized for the discovery of CDK9 inhibitors, some of which have entered human clinical trials. This review provides a comprehensive discussion on the structure and biology of CDK9, its role in solid and hematological cancers, and an updated review of the available inhibitors currently being investigated in preclinical and clinical settings.

Water borne cercaria(ae) of the trematode genus Schistosoma rapidly penetrate host skin. A single serine protease activity, cercarial elastase, is deposited in advance of the invading parasite by holocytosis of vesicles from ten large acetabular gland cells. Cercarial elastase activity is a composite of multiple isoforms. Genes coding for the isoforms can be divided into two classes by amino acid and promoter sequence homology. Two of the five genes identified in Schistosoma mansoni account for over 90% of the activity and protein released. The remaining genes produce little protein or are silent. Positional scanning synthetic combinatorial substrate libraries demonstrate that the two major isoforms have similar substrate specificities and are, therefore, isoenzymes. The closely related Schistosoma hematobium and the distantly related Schistosomatium douthitti also contain multiple orthologous cercarial elastase genes suggesting that gene duplication may have occurred after speciation in Schistosoma evolution and that this duplication has been conserved.Cercaria(e), the aquatic infective larval stage of schistosomes, are highly adapted to rapidly penetrate the skin of the host upon contact. Enzymatic hydrolysis of host proteins is required for successful entry into the host vascular system (1). Two gland systems, the preacetabular and postacetabular glands, release proteases and comprise the majority of the volume of the cercarial head. Each gland cell releases proteases at the leading edge of the invading parasite through long, microtubule-lined cell processes or "ducts" that exit at the anterior head (2). The postacetabular glands are also responsible for depositing mucin, providing an adhesive surface on the skin for the parasite to initially attach. Considering the diverse set of macromolecular barriers the cercariae must breach during invasion, we previously investigated the possibility that multiple enzyme activities were required. However, only a single protease activity, cercarial elastase, was found to be present in acetabular gland secretions and required for invasion (3).Cercarial elastase is a trypsin family serine protease named because of its ability to cleave insoluble elastin, a major component of the dermis of skin (4, 5). Its P1 substrate specificity (1) is for large hydrophobic side chains, but in contrast to chymotrypsin (3) cercarial elastase is more active against macromolecular substrates than synthetic tetrapeptides.We examined the complement of genes coding for cercarial elastase in Schistosoma mansoni and found a family of isoforms that can be divided into two classes by amino acid and promoter sequence homology. This family of genes is also conserved in another schistosome species Schistosoma hematobium and Schistosomatium douthitti. The two most highly expressed S. mansoni isoforms comprise Ͼ90% of the released activity and are virtually identical in biochemical properties.

Phosphorylation of eIF4E by human mitogen-activated protein kinase (MAPK)-interacting kinases (Mnks) is crucial for human tumourigenesis and development. Targeting Mnks may provide a novel anticancer therapeutic strategy. However, the lack of selective Mnk inhibitors has so far hampered pharmacological target validation and clinical drug development. Herein, we report, for the first time, the discovery of a series of 5-(2-(phenylamino)pyrimidin-4-yl)thiazole-2(3H)-one derivatives as Mnk inhibitors. Several derivatives demonstrate very potent Mnk2 inhibitory activity. The most active and selective compounds were tested against a panel of cancer cell lines, and the results confirm the cell-type-specific effect of these Mnk inhibitors. Detailed cellular mechanistic studies reveal that Mnk inhibitors are capable of reducing the expression level of anti-apoptotic protein Mcl-1, and of promoting apoptosis in MV4-11 acute myeloid leukaemia cells.

Serine proteases are considered to be involved in plasticity-related events in the nervous system, but their in vivo targets and the importance of their control by endogenous inhibitors are still not clarified. Here, we demonstrate the crucial role of a potent serine protease inhibitor, protease nexin-1 (PN-1), in the regulation of activity-dependent brain proteolytic activity and the functioning of sensory pathways. Neuronal activity regulates the expression of PN-1, which in turn controls brain proteolytic activity. In PN-1 Ϫ/Ϫ mice, absence of PN-1 leads to increased brain proteolytic activity, which is correlated with an activity-dependent decrease in the NR1 subunit of the NMDA receptor. Correspondingly, reduced NMDA receptor signaling is detected in their barrel cortex. This is coupled to decreased sensory evoked potentials in the barrel cortex and impaired whisker-dependent sensory motor function. Thus, a tight control of serine protease activity is critical for the in vivo function of the NMDA receptors and the proper function of sensory pathways.

Cyclin-dependent kinase 9 (CDK9) is a key transcriptional regulator and a lucrative target for cancer treatment. Targeting CDK9 can effectively confine the hyperactivity of androgen receptor and the constitutive expression of anti-apoptotic proteins; both being main causes of prostate cancer (PCa) development and progression. In castrate-resistant PCa, traditional therapies that only target androgen receptor (AR) have become obsolete due to reprograming in AR activity to make the cells independent of androgen. CDK9 inhibitors may provide a new and better therapeutic opportunity over traditional treatment options by targeting both androgen receptor activity and antiapoptotic proteins, improving the chances of positive outcomes, especially in patients with the advanced disease. This review focuses on biological functions of CDK9, its involvement with AR and the potential for therapeutic opportunities in PCa treatment.

The recent demonstration of the anti-oxidant properties of the Bcl-2 gene product suggested that expression of Bcl-2 may interfere with the nuclear migration of the NF-KB transcription factor, which is thought to depend on the presence of reactive oxygen intermediates. In mouse L cells, overexpression of B&2 interfered with the activation of NF-KB by H,O,. However, B&2 had no effect on the activation of NF-cB by TNF, even though it protected cells from TNF-induced apoptosis. The effects of exogenous pyrrolidine dithiocarbamate were very similar to those of B&2 overexpression. We conclude that the protective effects of anti-oxidants against induced apoptotic cell death are unrelated to their ability to interfere with NF-KB activation.

Selective abrogation of cyclin-dependent kinases (CDK) activity is a highly promising strategy in cancer treatment. The atypical CDK, CDK5 has long been known for its role in neurodegenerative diseases, and is becoming an attractive drug target for cancer therapy. Myriads of recent studies have uncovered that aberrant expression of CDK5 contributes to the oncogenic initiation and progression of multiple solid and hematological malignancies. CDK5 is also implicated in the regulation of cancer stem cell biology. In this review, we present the current state of knowledge of CDK5 as a druggable target for cancer treatment. We also provide a detailed outlook of designing selective and potent inhibitors of this enzyme.