Structural features and conformational equilibria of 310-helical peptides in solution by spectroscopic and molecular mechanics studies

The structural features and conformational equilibria of a series of short, linear Calpha-methylvaline [(alphaMe)Val]-based peptides in methanol were investigated by combining fluorescence resonance energy transfer measurements and molecular mechanics data. IR spectra were employed to determine their secondary structure, which exhibits an intramolecularly H-bonded, 3(10)-helix conformation that is affected by backbone distortions that are enhanced by the shortness of the main chain.     

ARFGAP1 promotes the formation of COPI vesicles,suggesting function as a component of the coat

The role of GTPase-activating protein (GAP) that deactivates ADP-ribosylation factor 1 (ARF1) during the formation of coat protein I (COPI) vesicles has been unclear. GAP is originally thought to antagonize vesicle formation by triggering uncoating, but later studies suggest that GAP promotes cargo sorting, a process that occurs during vesicle formation. Recent models have attempted to reconcile these seemingly contradictory roles by suggesting that cargo proteins suppress GAP activity during vesicle formation, but whether GAP truly antagonizes coat recruitment in this process has not been assessed directly. We have reconstituted the formation of COPI vesicles by incubating Golgi membrane with purified soluble components, and find that ARFGAP1 in the presence of GTP promotes vesicle formation and cargo sorting. Moreover, the presence of GTPgammaS not only blocks vesicle uncoating but also vesicle formation by preventing the proper recruitment of GAP to nascent vesicles. Elucidating how GAP functions in vesicle formation, we find that the level of GAP on the reconstituted vesicles is at least as abundant as COPI and that GAP binds directly to the dilysine motif of cargo proteins. Collectively, these findings suggest that ARFGAP1 promotes vesicle formation by functioning as a component of the COPI coat.     

High-throughput proteomic analysis of human infiltrating ductal carcinoma of the breast

Large-scale proteomics will play a critical role in the rapid display, identification and validation of new protein targets, and elucidation of the underlying molecular events that are associated with disease development, progression and severity. However, because the proteome of most organisms are significantly more complex than the genome, the comprehensive analysis of protein expression changes will require an analytical effort beyond the capacity of standard laboratory equipment. We describe the first high-throughput proteomic analysis of human breast infiltrating ductal carcinoma (IDCA) using OCT (optimal cutting temperature) embedded biopsies, two-dimensional difference gel electrophoresis (2-D DIGE) technology and a fully automated spot handling workstation. Total proteins from four breast IDCAs (Stage I, IIA, IIB and IIIA) were individually compared to protein from non-neoplastic tissue obtained from a female donor with no personal or family history of breast cancer. We detected differences in protein abundance that ranged from 14.8% in stage I IDCA versus normal, to 30.6% in stage IIB IDCA versus normal. A total of 524 proteins that showed > or = three-fold difference in abundance between IDCA and normal tissue were picked, processed and identified by mass spectrometry. Out of the proteins picked, approximately 80% were unambiguously assigned identities by matrix-assisted laser desorbtion/ionization-time of flight mass spectrometry or liquid chromatography-tandem mass spectrometry in the first pass. Bioinformatics tools were also used to mine databases to determine if the identified proteins are involved in important pathways and/or interact with other proteins. Gelsolin, vinculin, lumican, alpha-1-antitrypsin, heat shock protein-60, cytokeratin-18, transferrin, enolase-1 and beta-actin, showed differential abundance between IDCA and normal tissue, but the trend was not consistent in all samples. Out of the proteins with database hits, only heat shock protein-70 (more abundant) and peroxiredoxin-2 (less abundant) displayed the same trend in all the IDCAs examined. This preliminary study demonstrates quantitative and qualitative differences in protein abundance between breast IDCAs and reveals 2-D DIGE portraits that may be a reflection of the histological and pathological status of breast IDCA.     

Triazines facilitate neurotransmitter release of synaptic terminals located in hearts of frog (Rana ridibunda) and honeybee (Apis mellifera) and in the ventral nerve cord of a beetle (Tenebrio molitor)

Three triazine herbicides, atrazine, simazine and metribuzine, and some of their major metabolites (cyanuric acid and 6-azauracil) were investigated for their action on synaptic terminals using three different isolated tissue preparations from the atria of the frog, Rana ridibunda, the heart of the honeybee, Apis mellifera macedonica, and the ventral nerve cord of the beetle, Tenebrio molitor. The results indicate that triazines facilitate the release of neurotransmitters from nerve terminals, as already reported for the mammalian central nervous system. The no observed effect concentration, the maximum concentration of the herbicide diluted in the saline that has no effect on the physiological properties of the isolated tissue, was estimated for each individual preparation. According to their relative potency, the three triazines tested can be ranked as follows: atrazine (cyanuric acid), simazine>metribuzine (6-azauracil). The action of these compounds on the cholinergic (amphibians, insects), adrenergic (amphibian) and octopaminergic (insects) synaptic terminals is discussed.     

Cyclic amine sulfonamides as linkers in the design and synthesis of novel human beta(3) adrenergic receptor agonists

Piperidine, pyrrolidine, and azetidine sulfonamides were examined as linkers in designing novel human beta(3) adrenergic receptor (beta(3)-AR) agonists. The azetidine derivative 37, and piperidine derivatives 7, 8, and 13 were found to be potent beta(3)-AR agonists and have good selectivity against beta(1)- and beta(2)-AR.     

A spectroscopic and molecular mechanics investigation on a series of AIB-based linear peptides and a peptide template, both containing tryptophan and a nitroxide derivative as probes

Linear Aib-based hexapeptides, of the general formula Ac-Toac-(Aib)(n) -Trp-(Aib)(r) -OtBu [T(Aib)(n) Trp], where n + r = 4, and Toac is a nitroxide spin-labeled C(alpha,alpha)-disubstituted glycine, were investigated by steady-state and time-resolved fluorescence measurements in different solvent media. A related peptide, i.e., cyclo-?Orn-[(Aib)(2)-Trp-(Aib)(2)-Z]-Asp-[(Aib)(2)-Toac-(Aib)(2)-+ ++OtBu ]? [T-cyclo-Trp], was also studied by the same techniques. It is a L-Orn, L-Asp diketopiperazine template, to which two Aib-based chains are covalently attached, each one containing one chromophore only, i.e., Trp or Toac. Whatever the solvent, in the former series of peptides quenching of the excited Trp exhibits three lifetime components and proceeds on a time scale from subnanoseconds to a few nanoseconds, while in the case of the template the same process occurs entirely on the nanoscale time scale, exhibiting two lifetimes only. The ir absorption spectral patterns suggest that the backbone of the peptides examined is in the 3(10)-helical conformation, as earlier determined by x-ray diffraction for T(Aib)(3)Trp in the crystal state. In all cases, the fluorescence results are satisfactorily described by a dipole-dipole interaction mechanism, in which electronic energy transfer takes place from the excited Trp to Toac, provided the mutual orientation between the fluorophore and Toac is taken into account. This implies that interconversion among conformational substates is slow on the time scale of the transfer process, allowing us to estimate the dynamics of the process. Molecular mechanics calculations coupled with time decay data made it possible to build up the most probable structures of these peptides in solution.     

Aflp markers tightly linked to the sex locus in Asparagus officinalis L.

Nine AFLP markers linked to the sex locus in Asparagus officinalis L. have been identified by non-radioactive AFLP technique and bulked segregant analysis. A composite map of one F₂ and two F₁ populations identified three very tightly linked markers. These markers did not give recombinants in the three different populations and mapped 0.5, 0.7 and 1 cM to the sex locus. Codominant scoring of the markers in the F₂ population from a selfed andromonoecious plant could distinguish the XX, XY and YY asparagus plants. The AFLP markers were isolated from the gel and cloned into plasmid vectors. The marker E41M50, which is a low-copy sequence and did not give any recombinants in the screened populations, detected polymorphism between female and male plants when used as RFLP probe. The AFLP markers we obtained are important to plant breeding, particularly in the development of sex specific PCR primers that could be used in the screening of different asparagus plants at the seedling stage. They are likewise important in the elucidation of the mechanisms underlying sex determination and differentiation in this species.     

Kit signaling through PI 3-kinase and Src kinase pathways: an essential role for Rac1 and JNK activation in mast cell proliferation.

The receptor tyrosine kinase Kit plays critical roles in hematopoiesis, gametogenesis and melanogenesis. In mast cells, Kit receptor activation mediates several cellular responses including cell proliferation and suppression of apoptosis induced by growth factor deprivation and gamma-irradiation. Kit receptor functions are mediated by kinase activation, receptor autophosphorylation and association with various signaling molecules. We have investigated the role of phosphatidylinositol 3'-kinase (PI 3-kinase) and Src kinases in Kit-mediated cell proliferation and suppression of apoptosis induced both by factor deprivation and irradiation in bone marrow-derived mast cells (BMMC). Analysis of Kit-/- BMMC expressing mutant Kit receptors and the use of pharmacological inhibitors revealed that both signaling pathways contribute to these Kit-mediated responses and that elimination of both pathways abolishes them. We demonstrate that the PI 3-kinase and Src kinase signaling pathways converge to activate Rac1 and JNK. Analysis of BMMC expressing wild-type and dominant-negative mutant forms of Rac1 and JNK revealed that the Rac1/JNK pathway is critical for Kit ligand (KL)-induced proliferation of mast cells but not for suppression of apoptosis. In addition, KL was shown to inhibit sustained activation of JNK induced by gamma-irradiation and concomitant irradiation-induced apoptosis.     

Effects of Bothrops asper snake venom on the expression of cyclooxygenases and production of prostaglandins by peritoneal leukocytes in vivo,and by isolated neutrophils and macrophages in vitro

In this study, the ability of Bothrops asper snake venom (BaV) to increase the production of prostaglandins PGE₂ and PGD₂ was assessed in a mouse model in vivo and in inflammatory cells in vitro. In addition, the expressions of COX-1 and COX-2 were assessed. BaV induced an increment in the in vivo synthesis of PGE₂ and PGD₂, together with an enhanced expression of COX-2, but not of COX-1. However, enzymatic activities of COX-1 and COX-2 were increased. Incubation of isolated macrophages and neutrophils with a sub-cytotoxic concentration of BaV in vitro resulted in increased release of PGE₂ and PGD₂ by macrophages and PGE₂ by neutrophils, concomitantly with an increment in the expression of COX-2, but not of COX-1 by both cell types. Our results demonstrate the ability of BaV to promote the expression of COX-2 and to induce the synthesis of proinflammatory prostaglandins. Macrophages and neutrophils may be important targets for this venom under in vivo situation.