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J Bioenerg Biomembr,
2005]
The V-ATPases are ATP-dependent proton pumps present in both intracellular compartments and the plasma membrane. They function in such processes as membrane traffic, protein degradation, renal acidification, bone resorption and tumor metastasis. The V-ATPases are composed of a peripheral V(1) domain responsible for ATP hydrolysis and an integral V(0) domain that carries out proton transport. Our recent work has focused on structural analysis of the V-ATPase complex using both cysteine-mediated cross-linking and electron microscopy. For cross-linking studies, unique cysteine residues were introduced into structurally defined sites within the B and C subunits and used as points of attachment for the photoactivated cross-linking reagent MBP. Disulfide mediated cross-linking has also been used to define helical contact surfaces between subunits within the integral V(0) domain. With respect to regulation of V-ATPase activity, we have investigated the role that intracellular environment, luminal pH and a unique domain of the catalytic A subunit play in controlling reversible dissociation in vivo.
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Mol Reprod Dev,
1990]
Caenorhabditis elegans develops from the embryo, through four larval stages that are punctuated by molts, then to adulthood. There are two sexes: hermaphrodites and males. Hermaphrodites may reproduce by self-fertilization or they may mate with males to produce cross-progeny...
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Acta Biochimica Polonica,
2005]
Carbohydrates are known as sources of immunological cross-reactivity of allergenic significance. In celery and in cypress pollen, the major allergens Api g 5 and Cup a 1 are recognised by antisera raised against anti-horseradish peroxidase and by patients'''' IgE which apparently bind carbohydrate epitopes; mass spectrometric analysis of the tryptic peptides and of their N-glycans showed the presence of oligosaccharides carrying both xylose and core alpha 1,3-fucose residues. Core alpha 1,3-fucose residues are also a feature of invertebrates: genetic and biochemical studies on the fruitfly Drosophila melanogaster, the parasitic trematode Schistosoma mansoni and the nematode worm Caenorhabditis elegans indicate that these organisms possess core alpha 1,3-fucosyltransferases. Various experiments have shown that fucosyltransferases from both fly and worm are responsible in vivo and in vitro for the synthesis of N-glycans which cross-react with anti-horseradish peroxidase; thus, we can consider these enzymes as useful tools in generating standard compounds for testing cross-reactive carbohydrate epitopes of
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Eur J Cell Biol,
2010]
The basement membrane (BM) is a dense, tightly cross-linked matrix that acts as physiological barrier to maintain tissue homeostasis. Studies on Caenorhabditis elegans, leucocytes diapedesis and cancer cell invasion have shown that BM transmigration is a conserved three-stage process. Firstly, invadopodia-like protrusions form at the ventral surface of invasive cells; later, one protrusion elongates that lastly drives the infiltration of cells into the underlying compartment. This review illustrates the mechanism used by invasive cancer cells to cross the BM barrier by focusing on the role of key cytoskeleton components. We also describe currently available in vitro assays to study each step of the BM transmigration program.
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Cell Microbiol,
2015]
Cross-kingdom interactions between bacteria and fungi are a common occurrence in the environment. Recent studies have identified various types of interactions that either can take the form of a synergistic relationship or can result in an antagonistic interplay with the subsequent destruction or inhibition of growth of bacteria, fungi or both. This cross-kingdom communication is of particular significance in human health and disease, as bacteria and fungi commonly colonize various human surfaces and their interactions can at times alter the outcome of invasive infections. Moreover, mixed infections from both bacteria and fungi are relatively common among critically ill patients and individuals with weak immune responses. The purpose of this review is to summarize our knowledge on the type of interactions between bacteria and fungi and their relevance in human infections.
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WormBook,
2007]
The nematode cuticle is an extremely flexible and resilient exoskeleton that permits locomotion via attachment to muscle, confers environmental protection and allows growth by molting. It is synthesised five times, once in the embryo and subsequently at the end of each larval stage prior to molting. It is a highly structured extra-cellular matrix (ECM), composed predominantly of cross-linked collagens, additional insoluble proteins termed cuticlins, associated glycoproteins and lipids. The cuticle collagens are encoded by a large gene family that are subject to strict patterns of temporal regulation. Cuticle collagen biosynthesis involves numerous co- and post-translational modification, processing, secretion and cross-linking steps that in turn are catalysed by specific enzymes and chaperones. Mutations in individual collagen genes and their biosynthetic pathway components can result in a range of defects from abnormal morphology (dumpy and blister) to embryonic and larval death, confirming an essential role for this structure and highlighting its potential as an ECM experimental model system.
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Curr Opin Immunol,
2004]
Until very recently it was not known whether the invertebrate Caenorhabditis elegans was capable of mounting a specific immune response to protect itself from pathogens. It has only just become clear that this simple nematode in fact possesses a complex innate immune system, involving multiple signalling pathways and an armoury of antimicrobial proteins and peptides. Genetic and microarray approaches are now revealing the molecular cross-talk that exists between the different signalling cascades.
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Methods Cell Biol,
1995]
The number of easily distinguishable mutant phenotypes in Caenorhabditis elegans is relatively small, and this constrains the number of factors that can be followed in standard genetic crosses. Consequently, a new mutation is mapped, first to a chromosome using two-factor data from one or more crosses, and then to a chromosomal subregion by successive three-factor crosses. Mapping would be more efficient if it were possible to score a large number of well-distributed markers in a single cross. The advent of the polymerase chain reaction makes this approach feasible by allowing polymorphic genomic regions to serve as genetic markers that are easily scored in DNA released from individual animals. The only "phenotype" is a band on a gel, so the segregation of many of these markers can be followed in a single cross. Following the terminology proposed by Olsen et al. (1989), we refer to polymorphisms that can be scored by appropriately designed polymerase chain reaction (PCR) assays as polymorphic seqeunce-tagged sites (STSs)...
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Cold Spring Harbor Symposia on Quantitative Biology,
1982]
The capping of cross-linked surface receptors on lymphocytes and other cells and the centripetal movement of surface-attached particles on crawling cells are examples of directed surface membrane movement. One possible mechanism for moving membrane components is that cytoskeletal proteins recognize cross-linked surface receptors and drag them through the membrane bilayer to one pole of the cell. Favoring this theory are the localization of actin and/or myosin under capped or mobile cross-linked surface molecules and the biochemical coisolation of actin with capped proteins. Another possibility is that movement results from flow of bulk membrane or membrane lipid between an assembly point at one pole of the cell to a disassembly point elsewhere on the surface. Capping on sessile cells and rearward membrane movement on crawling cells have different functions. The clustering of surface receptors that occurs during capping seems to play a role in the transmission of signals from surface-bound ligands across the membrane. As pointed out by Abercrombie, membrane movement on crawling cells may participate in locomotion. Crawling requires continuous assembly of new cell-substrate contact sites at the leading edge of the cell. Rearward membrane movement would result from this polarized membrane assembly. Thus, it is reasonable that these two types of direct membrane movement could be driven by different mechanisms, with cytoskeletal linkage operating in sessile cells and membrane flow occurring on crawling cells. This notion is supported by studies showing two distinct mechanisms for capping, one occurring spontaneously on motile cells and the other requiring ligand cross-linkage on lymphocytes. Here we examine the surface membrane movements on the amoebid spermatozoon of the free-living nematode Caenorhabditis elegans. This cell exhibits a pronounced morphological asymmetry, with the cellular organelles segregated into a hemispherical cell body (3-4 um dia). The cell forms a single persistent pseudopod, filled with granular cytoplasm, that extends about 4 um. Three features make the C. elegans spermatozoon ideal for studying the crawling movements of metazoan cells. First, differentiation of sessile, spherical spermatids into spermatozoa can be activated in vitro with the monovalent ion ionophore monensin so that the onset of motility can be controlled. Second, the asymmetry of the cell is clearly defined with the cell-body-pseuodopod junction visible both externally and internally. Third, sperm-defective mutants can be isolated, allowing cellular motility to be analyzed genetically. We now report that surface membrane movement on C. elegans spermatozoa occurs exclusively on the pseudopod. This movement comprises centripetal bulk-membrane flow and is not restricted to rearrangement of cross-linked membrane components. Furthermore, surface
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Curr Opin Cell Biol,
1996]
One major challenge in the fields of signal transduction and pattern formation is to understand how multiple signals are integrated to determine cell fates. Two developmental systems, vulval development in Caenorhabditis elegans and axis formation during Drosophila melanogaster oogenesis, require the epidermal growth factor receptor tyrosine kinase and the NOTCH signaling pathways to specify cell fates. Current work in both systems has provided new opportunities to investigate the potential for the cross-talk between these different signaling pathways.