Phosphorylation-dependent proline isomerization catalyzed by Pin1 is essential for tumor cell survival and entry into mitosis.

Pin1, a member of the parvulin family of peptidyl-prolyl cis-trans isomerases (PPIases) has been implicated in the G2-M transition of the mammalian cell cycle. Pin1 interacts with a series of mitotic phosphoproteins, including Polo-like kinase-1, Cdc25C, and Cdc27, and is thought to act as a phosphorylation-dependent PPIase for these target molecules. Pin1 recognizes phosphorylated serine-proline or threonine-proline peptide-bonds in test substrates up to 1300-fold better than in the respective unphosphorylated peptides. To test directly whether Pin1 regulates the G2-M transition and/or progression through mitosis by catalyzing phosphorylation-dependent prolyl isomerization of essential mitotic targets, we examined the consequences of Pin1 depletion, achieved by (a) overexpression of Pin1 antisense RNA, (b) overexpression of dominant-negative Pin1, and (c) by a known small-molecule Pin1-PPIase inhibitor, juglone. The results of all of the three lines of investigation show that the catalytic activity of Pin1 is essential for tumor cell survival and entry into mitosis.     

Genome sequence of Rheinheimera sp. strain A13L, isolated from Pangong Lake, India

Rheinheimera sp. strain A13L, which has antimicrobial activity, was isolated from alkaline brackish water of the high-altitude Pangong Lake of Ladakh, India. Here we report the draft genome sequence of Rhienheimera sp. strain A13L (4,523,491 bp with a G+C content of 46.23%). The genome is predicted to contain genes for marinocine and colicin V production, which may be responsible for the antimicrobial activity of the strain.     

Inhibition of polyamine oxidase prevented cyclin-dependent kinase inhibitor-induced apoptosis in HCT 116 colon carcinoma cells

Roscovitine and purvalanol are novel cyclin-dependent kinase (CDK) inhibitors that prevent cell proliferation and induce apoptotic cell death in various cancer cell lines. Although a number of studies have demonstrated the potential apoptotic role of roscovitine, there is limited data about the therapeutic efficiency of purvalanol on cancer cells. The natural polyamines (PAs) putrescine, spermidine, and spermine have essential roles in the regulation of cell differentiation, growth, and proliferation, and increased levels of these compounds have been associated with cancer progression. Recently, depletion of intracellular PA levels because of modulation of PA catabolic enzymes was shown to be an indicator of the efficacy of chemotherapeutic agents. In this study, our aim was to investigate the potential role of PA catabolic enzymes in CDK inhibitor-induced apoptosis in HCT 116 colon carcinoma cells. Exposure of cells to roscovitine or purvalanol decreased cell viability in a dose- and time-dependent manner. The selected concentrations of roscovitine and purvalanol inhibited cell viability by 50 % compared with control cells and induced apoptosis by activating the mitochondria-mediated pathway in a caspase-dependent manner. However, the apoptotic effect of purvalanol was stronger than that of roscovitine in HCT 116 cells. In addition, we found that CDK inhibitors decreased PA levels and significantly upregulated expression of key PA catabolic enzymes such as polyamine oxidase (PAO) and spermine oxidase (SMO). MDL-72,527, a specific inhibitor of PAO and SMO, decreased apoptotic potential of CDK inhibitors on HCT 116 cells. Moreover, transient silencing of PAO was also reduced prevented CDK inhibitor-induced apoptosis in HCT 116 cells. We conclude that the PA catabolic pathway, especially PAO, is a critical target for understanding the molecular mechanism of CDK inhibitor-induced apoptosis.     

One Target—Two Different Binding Modes: Structural Insights into Gevokizumab and Canakinumab Interactions to Interleukin-1β

Interleukin-1β (IL-1β) is a key orchestrator in inflammatory and several immune responses. IL-1β exerts its effects through interleukin-1 receptor type I (IL-1RI) and interleukin-1 receptor accessory protein (IL-1RAcP), which together form a heterotrimeric signaling-competent complex. Canakinumab and gevokizumab are highly specific IL-1β monoclonal antibodies. Canakinumab is known to neutralize IL-1β by competing for binding to IL-1R and therefore blocking signaling by the antigen:antibody complex. Gevokizumab is claimed to be a regulatory therapeutic antibody that modulates IL-1β bioactivity by reducing the affinity for its IL-1RI:IL-1RAcP signaling complex. How IL-1β signaling is affected by both canakinumab and gevokizumab was not yet experimentally determined. We have analyzed the crystal structures of canakinumab and gevokizumab antibody binding fragment (Fab) as well as of their binary complexes with IL-1β. Furthermore, we characterized the epitopes on IL-1β employed by the antibodies by NMR epitope mapping studies. The direct comparison of NMR and X-ray data shows that the epitope defined by the crystal structure encompasses predominantly those residues whose NMR resonances are severely perturbed upon complex formation. The antigen:Fab co-structures confirm the previously identified key contact residues on IL-1β and provide insight into the mechanisms leading to their distinct modulation of IL-1β signaling. A significant steric overlap of the binding interfaces of IL-1R and canakinumab on IL-1β causes competitive inhibition of the association of IL-1β and its receptor. In contrast, gevokizumab occupies an allosteric site on IL-1β and complex formation results in a minor reduction of binding affinity to IL-1RI. This suggests two different mechanisms of IL-1β pathway attenuation.     

S9A Serine Protease Engender Antigenic Gluten Catabolic Competence to the Human Gut Microbe

The human gut microbiome has a significant role in host physiology; however its role in gluten catabolism is debatable. Present study explores the role of human gut microbes in gluten catabolism and a native human gut microbe Cellulomonas sp. HM71 was identified. SSU rDNA analysis has described human gut microbiome structure and also confirmed the permanent residentship of Cellulomonas sp. HM71. Catabolic potential of Cellulomonas sp. HM71 to cleave antigenic gluten peptides indicates presence of candidate gene encoding biocatalytic machinery. Genome analysis has identified the presence of gene encoding S9A serine protease family—prolyl endopeptidase, with Ser591, Asp664 and His685 signature residues. Cellulomonas sp. HM71 prolyl endopeptidase activity was found optimal at pH 7.0 and 37 °C with a K_M of 35.53 μmol and specifically cleaves at proline residue. Current study describes the gluten catabolism potential of Cellulomonas sp. HM71 depicting possible role of human gut microbes in gluten catabolism to confer resistance mechanisms for the onset of celiac diseases in populations with gluten diet.     

Is serum fibroblast growth factor 21 associated with the severity or presence of coronary artery disease?

BackgroundRecent studies have shown that increased circulating concentrations of fibroblast growth factor 21 (FGF21) are associated with obesity, metabolic disorder, and atherosclerosis. However the relationship between FGF21 and coronary artery disease (CAD) is controversial This study was planned to investigate the role of FGF21 in CAD development and CAD severity.MethodsSeventy-eight patients with stable angina pectoris (SAP) (lesion positive) and 40 control patients (lesion negative) with similar cardiovascular risk factors were included in the study. Serum FGF21 levels were measured by ELISA method. CAD severity was evaluated by using SYNTAX and GENSINI risk scores.ResultsFGF21 concentrations were found significantly higher in the SAP group than in the control group. [101.18 ± 141.62 vs. 47.93 ± 58.74 pg/mL; p = 0.03], no correlation was found between the SYNTAX (r = 0.146 and p = 0.134) and GENSINI (r = 0.211 and p = 0.084) scores with serum FGF21 levels. There was a negative relationship between serum FGF21 and serum HDL-C levels in correlation analysis (r = - 0.272; p = 0.026).ConclusionsThe serum FGF21 levels are different between SAP and control patients. FGF21 is a marker for CAD diagnosis, but not for the evaluation of CAD severity.     

Retinol binding protein 4 levels relate to the presence and severity of coronary artery disease

BackgroundThe previous studies have showed that serum retinol binding protein 4 (RBP4) levels increase in metabolic disorders which are closely associated with cardiovascular diseases (CVD). However, the human studies investigating the role of RBP4 in CVD are conflicted. Therefore, we aimed to evaluate the relationship between RBP4 with the presence and severity of coronary artery disease (CAD) in this study.Methods55 patients with presenting acute coronary syndrome (ACS) and 43 control subjects who had various cardiovascular risk factors with normal coronary artery on coronary angiography were included in this study. The serum RBP4 concentrations were measured using ELISA method, clinically and anatomically score models were used to assess the severity of coronary lesion.ResultsSerum RBP4 levels were significantly higher in patients with ACS compared to the without ACS (68.40 ± 47.94 mg/L vs. 49.46 ± 13.64 mg/L; p = 0.014). RBP4 was correlated with GENSINI and SYNTAX I score (r = 0.286 p = 0.034; r = 0.403 p = 0.002 respectively). However, there was no relationship between RBP4 and GRACE score.ConclusionsThe serum RBP4 levels increase in patients with CAD and its increased levels may be correlated with CAD severity.     

mTOR is a fine tuning molecule in CDK inhibitors-induced distinct cell death mechanisms via PI3K/AKT/mTOR signaling axis in prostate cancer cells

Purvalanol and roscovitine are cyclin dependent kinase (CDK) inhibitors that induce cell cycle arrest and apoptosis in various cancer cells. We further hypothesized that co-treatment of CDK inhibitors with rapamycin, an mTOR inhibitor, would be an effective combinatory strategy for the inhibition of prostate cancer regard to androgen receptor (AR) status due to inhibition of proliferative pathway, PI3K/AKT/mTOR, and induction of cell death mechanisms. Androgen responsive (AR+), PTEN^?/? LNCaP and androgen independent (AR?), PTEN^+/? DU145 prostate cancer cells were exposed to purvalanol (20 µM) and roscovitine (30 µM) with or without rapamycin for 24 h. Cell viability assay, immunoblotting, flow cytometry and fluorescence microscopy was used to define the effect of CDK inhibitors with or without rapamycin on proliferative pathway and cell death mechanisms in LNCaP and DU145 prostate cancer cells. Co-treatment of rapamycin modulated CDK inhibitors-induced cytotoxicity and apoptosis that CDK inhibitors were more potent to induce cell death in AR (+) LNCaP cells than AR (?) DU145 cells. CDK inhibitors in the presence or absence of rapamycin induced cell death via modulating upstream PI3K/AKT/mTOR signaling pathway in LNCaP cells, exclusively only treatment of purvalanol have strong potential to inhibit both upstream and downstream targets of mTOR in LNCaP and DU145 cells. However, co-treatment of rapamycin with CDK inhibitors protects DU145 cells from apoptosis via induction of autophagy mechanism. We confirmed that purvalanol and roscovitine were strong apoptotic and autophagy inducers that based on regulation of PI3K/AKT/mTOR signaling pathway. Co-treatment of rapamycin with purvalanol and roscovitine exerted different effects on cell survival and death mechanisms in LNCaP and DU145 cell due to their AR receptor status. Our studies show that co-treatment of rapamycin with CDK inhibitors inhibit prostate cancer cell viability more effectively than either agent alone, in part, by targeting the mTOR signaling cascade in AR (+) LNCaP cells. In this point, mTOR is a fine-tuning player in purvalanol and roscovitine-induced apoptosis and autophagy via regulation of PI3K/AKT and the downstream targets, which related with cell proliferation.