Phosphorylcholine(PC)is an immunodominant epitope present on many proteins secreted(ES)by filarial nematodes and is thought to be involved in parasite survival by modulating the host immune response. Based on the postulate that nematodes producing ES lacking PC would have diminished survival time, studies were undertaken to investigate the mechanism of PC addition to ES. ES-62 is the major PC-containing ES product of Acanthocheilonema viteae (a rodent model of filariasis) and by investigating this molecule we have shown PC to be attacked to the protein backbone via an asparagine-linked glycan. This type of association between PC and carbohydrate is absent from humans and thus the PC-glycans of ES may pose a novel target for chemotherapy. Pulse-chase experiments have shown that PC addition to ES-62 is a fairly early event during intracellular trafficking occurring within 40-60 min of protein synthesis. Investigation employing inhibitors of intracellular trafficking and also oligosaccharide processing, has revealed three reagents capable of preventing attachment of PC to ES-62: Brefeldin A, which blocks transport from the ER to the golgi;1-deoxynojirimycin(dNM), which inhibits α-glucosidase I in the ER; and 1-deoxymannojirimycin, which inhibits α-mannosidase I in the cis Golgi. Swainsonine, an inhibitor of α-mannosidase II, does not interfere with PC transfer. Taken together these observations suggest that PC attachment is a post-ER event probably occurring in the medial Golgi and that the substrate for transfer is Man5GlcNAc3 or Man3GlcNAc3. Data from mass spectrometry are consistent with this interpretation and reveal that PC is attached to glycans containing a trimannosyl core, with or without core fucosylation and carrying between one and four additional GlcNAc residues.
In humans, Leishmania is an obligatory intracellular parasite of the mononuclear phagocyte system, wherein the microorganism multiplies. These pathogenic protozoa are transmitted by sandflies and reside in the digestive tract of the vector insects. There is increasing evidence that specialised surface and secreted molecules of Leishmania are virulence factors essential for colonization of the sandfly vector as well as for parasite invasion and subsequent survival in the macrophage. Recent research in our laboratories has focused on the identification and molecular characterisation of a unique family of mucin-like proteophosphoglycans (PPGs) present on the surface, and secreted by promastigotes and amastigotes. In this review we provide an overview of the current knowledge of the structure and function of this new class of proteoglycans. The elucidation of their primary structure reveals unique proteins, phosphoglycan structures and protein-carbohydrate linkages which, together with their proposed function(s), provide attractive targets for the development of vaccines and antiparasite drugs.
Angiogenesis, the production of new blood vessels, plays an important role in a number of physiological and pathologicalp rocesses, such as development, tissuer epair, inflammation, atherosclerosis and tumor progression. A number of mediators including cytokines, growth factors and others, have been implicated in angiogenesis. During tissue neovascularization, endothelial cells (EC) adhere to extracellular matrix (ECM) components and other ECs, which is an essential process in angiogenesis. Thus, in addition to soluble mediators mentioned above, ECM macromolecules and cellular adhesion molecules (CAMs) may also act as angiogenic factors. Among CAMs, E-selectin, vascular cell adhesion molecule(VCAM)-1, CD31, and some integrins may facilitate capillary formation both in vivo and in vitro. CAMs, as well as other angiogenic mediators may play a role in the pathogenesis of “angiogenic diseases”. Targeting of any of these factors may have potential therapeuticr elevance in such disorders.
During the year 1998, both the Japanese Patent Office (JPO) and United States Patent and Trademark Office (PTO) began offering on-line patent search capabilities on their websites free of charge. This has resulted in patent information being readily available to more people than ever before. Researchers, who never previously considered using patent data to supplement the basic literature, might be surprised at the wealth of underutilized information now avilable at no cost. Here, we attempt to provide the first time user with a general introduction to finding patent information on the Internet.