Structures of human MAP kinase kinase 1 (MEK1) and MEK2 describe novel noncompetitive kinase inhibition

MEK1 and MEK2 are closely related, dual-specificity tyrosine/threonine protein kinases found in the Ras/Raf/MEK/ERK mitogen-activated protein kinase (MAPK) signaling pathway. Approximately 30% of all human cancers have a constitutively activated MAPK pathway, and constitutive activation of MEK1 results in cellular transformation. Here we present the X-ray structures of human MEK1 and MEK2, each determined as a ternary complex with MgATP and an inhibitor to a resolution of 2.4 A and 3.2 A, respectively. The structures reveal that MEK1 and MEK2 each have a unique inhibitor-binding pocket adjacent to the MgATP-binding site. The presence of the potent inhibitor induces several conformational changes in the unphosphorylated MEK1 and MEK2 enzymes that lock them into a closed but catalytically inactive species. Thus, the structures reported here reveal a novel, noncompetitive mechanism for protein kinase inhibition.     

Synthesis, antimicrobial activity and conformational analysis of novel substituted pyridines: BF(3)-promoted reaction of hydrazine with 2-alkoxy pyridines

Some new 2-alkoxy-3-cyano-4,6-diarylpyridines 3,4 were synthesized by condensation of different alpha,beta-unsaturated ketones 1 with malononitrile 2, followed by cyclization in sodium alkoxide/alcohol system. Lewis acid-catalyzed reaction of 4 with hydrazine afforded the corresponding 1H-pyrazolo[3,4-b]pyridines 5. The potency of the results as antimicrobial agents has been evaluated. The structure of the newly prepared compounds was assessed by microanalysis, IR and NMR spectra. Molecular mechanics (MM2) and semiemperical (AM1) molecular orbital calculations have been performed for the most biologically active compounds 5b and c to get insight into their molecular structures and to learn more about their stable molecular conformations.     

Single-cell protein production from ram horn hydrolysate by bacteria

The alcoholysis (transesterification) of the refined cotton seed oil of Turkish origin with primary and secondary alcohols was investigated in the presence of an immobilized enzyme from Candida antarctica, commercially called Novozym 435 in a solvent-free medium. The optimum conditions of the methanolysis were as follows: 30% enzyme based on oil weight; oil/alcohol molar ratio 1:4; temperature: 50 degrees C and reaction time: 7 h. Maximum methyl esters (ME) yield was 91.5%. At the same conditions cotton seed oil was converted with short-chain primary and secondary alcohols to its corresponding esters with conversions between 72% and 94%. Our results indicated that alcoholysis products of cotton seed oil could be used as valuable intermediates in oleochemistry.     

Healing-promoting effect of bombesin treatment on chronic gastric ulcer in rats

To evaluate whether bombesin treatment has a facilitatory effect on the healing of chronic gastric ulcer, following the induction of ulcer by serosal application of acetic acid, rats were given bombesin (30 microg/kg/day; subcutaneously) or vehicle three times a day for 7, 14 or 21 days until they were decapitated. Neither food intake nor gastric emptying rate in either vehicle-treated or bombesin-treated groups was not statistically different from control rats. Similarly, ulcer indices and gastric myeloperoxidase (MPO) activities at the first and second weeks of injury were not different among the groups. However, in the 3-week ulcer group, bombesin treatment reduced tissue MPO level significantly back to control levels. Moreover, the analysis of the surface epithelium by scanning electron and light microscopy demonstrated a significant reduction in the severity of ulcers by bombesin treatment. Pretreatment with CCK antagonists (L-364,718 or L365,260; 25 micromol/kg/day) before bombesin treatment showed that neither of the CCK antagonists had a significant effect on the bombesin-mediated healing process, suggesting that CCK receptors are not involved in the action of bombesin. In accordance with the previous studies that show its acute gastroprotective effects, bombesin is also effective in promoting the healing process of chronic gastric ulcer in rats.     

The effects of streptozotocin-induced diabetes on brucellosis of rats

It is believed that an infection is more common and runs a more protracted course in people with diabetes. In clinical practice, it is important to be aware of these associations, as the prognosis is often dependent upon prompt recognition and appropriate treatment. To show the course of brucellosis in the diabetic state, a model of Brucella melitensis infection was used in the setting of streptozotocin-induced diabetes in rat. B. melitensis infection proceeded more severely in diabetic rats and the severity of diabetes affected the prognosis. However, no association was found between B. melitensis and insulin using in vitro and in vivo experiments. Our study illustrates that B. melitensis infection in diabetes should be taken seriously.     

Maintaining the immunological balance in parasitic infections: a role for TGF-beta?

Transforming growth factor beta (TGF-beta) is an important regulator of inflammation, being proinflammatory at low concentrations and anti-inflammatory at high concentrations. As such, TGF-beta might be important in maintaining the balance between control and clearance of infectious organisms on the one hand and prevention of immune-mediated pathology on the other. In this article, Fakhereldin Omer, J?rgen Kurtzhals and Eleanor Riley review the immunoregulatory properties of TGF-beta in the context of parasitic infections. Data from murine malaria infections suggest that TGF-beta modifies the severity of the disease, and a number of potential protective mechanisms are discussed. Evidence is accumulating that TGF-beta is important for the regulation of other host-parasite interactions and that parasites might directly influence TGF-beta-dependent pathways via the synthesis of TGF-beta or TGF-beta-receptor homologues.     

A Farnesyltransferase Inhibitor Induces Tumor Regression in Transgenic Mice Harboring Multiple Oncogenic Mutations by Mediating Alterations in Both Cell Cycle Control and Apoptosis

The farnesyltransferase inhibitor L-744,832 selectively blocks the transformed phenotype of cultured cells expressing a mutated H-ras gene and induces dramatic regression of mammary and salivary carcinomas in mouse mammary tumor virus (MMTV)–v-Ha-ras transgenic mice. To better understand how the farnesyltransferase inhibitors might be used in the treatment of human tumors, we have further explored the mechanisms by which L-744,832 induces tumor regression in a variety of transgenic mouse tumor models. We assessed whether L-744,832 induces apoptosis or alterations in cell cycle distribution and found that the tumor regression in MMTV–v-Ha-ras mice could be attributed entirely to elevation of apoptosis levels. In contrast, treatment with doxorubicin, which induces apoptosis in many tumor types, had a minimal effect on apoptosis in these tumors and resulted in a less dramatic tumor response. To determine whether functional p53 is required for L-744,832-induced apoptosis and the resultant tumor regression, MMTV–v-Ha-ras mice were interbred with p53^−/− mice. Tumors in ras/p53^−/− mice treated with L-744,832 regressed as efficiently as MMTV–v-Ha-ras tumors, although this response was found to be mediated by both the induction of apoptosis and an increase in G₁ with a corresponding decrease in the S-phase fraction. MMTV–v-Ha-ras mice were also interbred with MMTV–c-myc mice to determine whether ras/myc tumors, which possess high levels of spontaneous apoptosis, have the potential to regress through a further increase in apoptosis levels. The ras/myc tumors were found to respond nearly as efficiently to L-744,832 treatment as the MMTV–v-Ha-ras tumors, although no induction of apoptosis was observed. Rather, the tumor regression in the ras/myc mice was found to be mediated by a large reduction in the S-phase fraction. In contrast, treatment of transgenic mice harboring an activated MMTV–c-neu gene did not result in tumor regression. These results demonstrate that a farnesyltransferase inhibitor can induce regression of v-Ha-ras-bearing tumors by multiple mechanisms, including the activation of a suppressed apoptotic pathway, which is largely p53 independent, or by cell cycle alterations, depending upon the presence of various other oncogenic genetic alterations.