Synthesis and biological evaluation of a targeted library of protein phosphatase inhibitors

Phosphorylation of serine, threonine, and tyrosine controls fundamental mammalian cell events and is achieved by kinases which, in turn, are in dynamic relationship with phosphatases. Few selective inhibitors of protein tyrosine and dual specificity phosphatases are readily available. Based on SAR studies of naturally occurring phosphatase inhibitors and following up on previously published research, we have designed a new pharmacophore model V and synthesized a new library of functional analogues of V. All synthetic steps were carried out and optimized employing combinatorial chemistry methods on Wang resin. All compounds were tested in vitro for their ability to inhibit recombinant human protein tyrosine (PTP1B) and dual-specificity (Cdc25B(2) and VHR) phosphatases. Three of the approximately 70 compounds in our library inhibited Cdc25B(2) by 50% at 375-490 microM. No compounds inhibited PTP1B, and only one blocked VHR. Cell-culture studies revealed no toxicity to human breast cancer cells with two of the phosphatase inhibitors.     

A simple and economic preservation method for genomic bacterial DNA from clinically significant pathogens

Bacterial culture was allowed to dry to completeness on Columbia agar base with defibrinated horse blood. Following 6 months storage at room temperature, microbial DNA was extracted and successfully amplified by PCR. This storage technique has the advantage over other methods of not requiring (i) a DNA extraction protocol prior to storage and (ii) refrigeration and/or freezing. This technique maybe useful in the transportation of bacterial genomic DNA in nonviable cells as well as reliable method for the storage of DNA in underdeveloped countries.     

A rapid screening method to detect specific inhibitors of pyruvate orthophosphate dikinase as leads for C4 plant-selective herbicides

Plants using the C(4) photosynthetic pathway are highly represented among the world's worst weeds, with only 4 C(4) species being agriculturally productive (maize, sorghum, millet, and sugar cane). With the C(4) acid cycle operating as a biochemical appendage of C(3) photosynthesis, the additional enzymes involved in C(4) photosynthesis represent an attractive target for the development of weed-specific herbicides. The rate-limiting enzyme of this metabolic pathway is pyruvate orthophosphate dikinase (PPDK). PPDK, coupled with phosphoenolpyruvate carboxylase and nicotinamide adenine dinucleotide-malate dehydrogenase, was used to develop a microplate-based assay to detect inhibitors of enzymes of the C(4) acid cycle. The resulting assay had a Z' factor of 0.61, making it a high-quality assay able to reliably identify active test samples. Organic extracts of 6679 marine macroscopic organisms were tested within the assay, and 343 were identified that inhibited the 3 enzyme-coupled reaction. A high confirmation rate was achieved, with 95% of these hit extracts proving active again upon retesting. Sequential addition of phosphoenolpyruvate and oxaloacetate to the assay facilitated identification of 83 extracts that specifically inhibited PPDK.     

Identification of alternative pathway serum complement activity in the blood of the American alligator (Alligator mississippiensis)

Incubation of different dilutions of alligator serum with sheep red blood cells (SRBCs) that had not been sensitized with antibodies resulted in concentration-dependent hemolytic activity. This hemolytic activity was not affected by the presence of ammonium hydroxide and methylamine, known inactivators of the classical complement cascade. However, the hemolytic activities were inhibited by EDTA and salicylaldoxime, indicating that the alternate pathway is primarily responsible for these activities. Immunofixation of electrophoretically-resolved alligator serum proteins with antihuman C3 polyclonal antibodies resulted in detection of a protein antigenically similar to human C3 in alligator serum. SDS-PAGE, followed by Western blot analysis, revealed the presence of two alligator serum proteins with nearly identical molecular weights as human C3alpha and C3beta. SRBC hemolysis and antibacterial activity by alligator serum was significantly reduced in the presence of antihuman C3 antibodies. The hemolytic effect of alligator serum was shown to occur rapidly, with significant activity within 5 min and maximal activity occurring at 15 min. SRBC hemolysis was also temperature-dependent, with reduced activity below 15 degrees C and above 30 degrees C. These data suggest that the antibiotic properties of alligator serum are partially due to the presence of a complement-facilitated humoral immune response analogous to that described in mammalian systems.     

N-WASP deficiency reveals distinct pathways for cell surface projections and microbial actin-based motility

The Wiskott-Aldrich syndrome protein (WASP) family of molecules integrates upstream signalling events with changes in the actin cytoskeleton. N-WASP has been implicated both in the formation of cell-surface projections (filopodia) required for cell movement and in the actin-based motility of intracellular pathogens. To examine N-WASP function we have used homologous recombination to inactivate the gene encoding murine N-WASP. Whereas N-WASP-deficient embryos survive beyond gastrulation and initiate organogenesis, they have marked developmental delay and die before embryonic day 12. N-WASP is not required for the actin-based movement of the intracellular pathogen Listeria but is absolutely required for the motility of Shigella and vaccinia virus. Despite these distinct defects in bacterial and viral motility, N-WASP-deficient fibroblasts spread by using lamellipodia and can protrude filopodia. These results imply a crucial and non-redundant role for N-WASP in murine embryogenesis and in the actin-based motility of certain pathogens but not in the general formation of actin-containing structures.