In the FVB/N HER-2/<Emphasis Type="Italic">neu</Emphasis> transgenic mouse both peripheral and central tolerance limit the immune response targeting HER-2/neu induced by <Emphasis Type="Italic">Listeria monocytogenes</Emphasis>-based vaccines

Listeria monocytogenes-based vaccines for HER-2/neu are capable of breaking tolerance in FVB/N rat HER-2/neu transgenic mice. The growth of implanted NT-2 tumors, derived from a spontaneously occurring tumor in the FVB/N HER-2/neu transgenic mouse, was significantly slower in these mice following vaccination with a series of L. monocytogenes-based vaccines for HER-2/neu. Mechanisms of T cell tolerance that exist in these transgenic mice include the absence of functional high avidity anti-HER-2/neu CD8⁺ T cells and the presence of CD4⁺CD25⁺ regulatory T cells. The in vivo depletion of these regulatory T cells resulted in the slowing in growth of tumors even without the treatment of mice with an anti-HER-2/neu vaccine. The average avidities of responsive CD8⁺ T cells to six of the nine epitopes in HER-2/neu we examined, four of which were identified in this study, are shown here to be of a lower average avidity in the transgenic mice versus wild type FVB/N mice. In contrast, the average avidity of CD8⁺ T cells to three epitopes that showed the lowest avidity in the wild-type mice did not differ between wild type and transgenic mice. This study demonstrates the ability of L. monocytogenes-based vaccines to impact upon tolerance to HER-2/neu in FVB/N HER-2/neu transgenic mice and further defines some of the aspects of tolerance in these mice.     

Novel excitatory Conus peptides define a new conotoxin superfamily

A new class of Conus peptides, the I-superfamily of conotoxins, has been characterized using biochemical, electrophysiological and molecular genetic methods. Peptides in this superfamily have a novel pattern of eight Cys residues. Five peptides that elicited excitatory symptomatology, r11a, r11b, r11c, r11d and r11e, were purified from Conus radiatus venom; four were tested on amphibian peripheral axons and shown to elicit repetitive action potentials, consistent with being members of the 'lightning-strike cabal' of toxins that effect instant immobilization of fish prey. A parallel analysis of Conus cDNA clones revealed a new class of conotoxin genes that was particularly enriched (with 18 identified paralogues) in a Conus radiatus venom duct library; several C. radiatus clones encoded the excitatory peptides directly characterized from venom. The remarkable diversity of related I-superfamily peptides within a single Conus species is unprecedented. When combined with the excitatory effects observed on peripheral circuitry, this unexpected diversity suggests a corresponding molecular complexity of the targeted signaling components in peripheral axons; the I-conotoxin superfamily should provide a rich lode of pharmacological tools for dissecting and understanding these. Thus, the I-superfamily conotoxins promise to provide a significant new technology platform for dissecting the molecular components of axons.     

Dimensionality reduction in computational demarcation of protein tertiary structures

Predictive classification of major structural families and fold types of proteins is investigated deploying logistic regression. Only five to seven dimensional quantitative feature vector representations of tertiary structures are found adequate. Results for benchmark sample of non-homologous proteins from SCOP database are presented. Importance of this work as compared to homology modeling and best-known quantitative approaches is highlighted.     

Design, synthesis, and biological evaluation of triazolopiperazine-based beta-amino amides as potent, orally active dipeptidyl peptidase IV (DPP-4) inhibitors

Various beta-amino amides containing triazolopiperazine heterocycles have been prepared and evaluated as potent, selective, orally active dipeptidyl peptidase IV (DPP-4) inhibitors. These compounds display excellent oral bioavailability and good overall pharmacokinetic profiles in preclinical species. Moreover, in vivo efficacy in an oral glucose tolerance test in lean mice is demonstrated.     

Erbin regulates mitogen-activated protein (MAP) kinase activation and MAP kinase-dependent interactions between Merlin and adherens junction protein complexes in Schwann cells

Biallelic mutations in the neurofibromatosis 2 (NF2) gene are linked to schwannoma and meningioma tumorigenesis. Cells with NF2 mutations exhibit elevated levels of phosphorylated extracellular signal-regulated kinase (ERK) and aberrant cell-cell and cell-matrix contacts. The NF2 gene product, merlin, associates with adherens junction protein complexes, suggesting that part of its function as a tumor suppressor involves regulating cell junctions. Here, we find that a novel PDZ protein, called erbin, binds directly to the merlin-binding partner, EBP0, and regulates adherens junction dissociation through a MAP kinase-dependent mechanism. Reducing erbin expression using a targeted siRNA in primary cultures of Schwann cells results in altered cell-cell interactions, disruption of E-cadherin adherens junctions, increased cell proliferation, and elevated levels of phosphorylated ERK, all phenotypes observed in cells that lack merlin. Reduction of erbin expression also results in the dissociation of merlin from adherens junction proteins and an increase in the levels of phosphorylated merlin. These phenotypes can be rescued if cells with reduced levels of erbin are treated with a pharmacological inhibitor of ERK kinase. Collectively, these data indicate that erbin regulates MAP kinase activation in Schwann cells and suggest that erbin links merlin to both adherens junction protein complexes and the MAP kinase signaling pathway.