Fragmentation of Golgi complex and Golgi autoantigens during apoptosis and necrosis

Anti-Golgi complex autoantibodies are found primarily in patients with Sjögren's syndrome and systemic lupus erythematosus, although they are not restricted to these diseases. Several Golgi autoantigens have been identified that represent a small family of proteins. Common features of all Golgi autoantigens appear to be their distinct structural organization of multiple α-helical coiled-coil rods in the central domains flanked by non-coiled-coil N-termini and C-termini, and their localization to the cytoplasmic face of Golgi cisternae. Many autoantigens in systemic autoimmune diseases have distinct cleavage products in apoptosis or necrosis and this has raised the possibility that cell death may play a role in the generation of potentially immunostimulatory forms of autoantigens. In the present study, we examined changes in the Golgi complex and associated autoantigens during apoptosis and necrosis. Immunofluorescence analysis showed that the Golgi complex was altered and developed distinctive characteristics during apoptosis and necrosis. In addition, immunoblotting analysis showed the generation of antigenic fragments of each Golgi autoantigen, suggesting that they may play a role in sustaining autoantibody production. Further studies are needed to determine whether the differences observed in the Golgi complex during apoptosis or necrosis may account for the production of anti-Golgi complex autoantibodies.     

Autoantibodies against the replication protein A complex in systemic lupus erythematosus and other autoimmune diseases

Replication protein A (RPA), a heterotrimer with subunits of molecular masses 70, 32, and 14 kDa, is a single-stranded-DNA-binding factor involved in DNA replication, repair, and recombination. There have been only three reported cases of anti-RPA in systemic lupus erythematosus (SLE) and Sjögren syndrome (SjS). This study sought to clarify the clinical significance of autoantibodies against RPA. Sera from 1,119 patients enrolled during the period 2000 to 2005 were screened by immunoprecipitation (IP) of ³⁵S-labeled K562 cell extract. Antigen-capture ELISA with anti-RPA32 mAb, immunofluorescent antinuclear antibodies (ANA) and western blot analysis with purified RPA were also performed. Our results show that nine sera immunoprecipitated the RPA70–RPA32–RPA14 complex and all were strongly positive by ELISA (titers 1:62,500 to 1:312,500). No additional sera were positive by ELISA and subsequently confirmed by IP or western blotting. All sera showed fine speckled/homogeneous nuclear staining. Anti-RPA was found in 1.4% (4/276) of SLE and 2.5% (1/40) of SjS sera, but not in rheumatoid arthritis (0/35), systemic sclerosis (0/47), or polymyositis/dermatomyositis (0/43). Eight of nine patients were female and there was no racial predilection. Other positive patients had interstitial lung disease, autoimmune thyroiditis/hepatitis C virus/pernicious anemia, or an unknown diagnosis. Autoantibody specificities found in up to 40% of SLE and other diseases, such as anti-nRNP, anti-Sm, anti-Ro, and anti-La, were unusual in anti-RPA-positive sera. Only one of nine had anti-Ro, and zero of nine had anti-nRNP, anti-Sm, anti-La, or anti-ribosomal P antibodies. In summary, high titers of anti-RPA antibodies were found in nine patients (1.4% of SLE and other diseases). Other autoantibodies found in SLE were rare in this subset, suggesting that patients with anti-RPA may form a unique clinical and immunological subset.     

Speciation in sexually deceptive orchids: pollinator-driven selection maintains discrete odour phenotypes in hybridizing species

Ophrys orchids mimic the female sex pheromones of their pollinator species to attract males for pollination. Reproductive isolation in Ophrys is based on the selective attraction of only a single pollinator species. A change of floral odour can result in the attraction of a new pollinator species that acts as an isolation barrier towards other sympatrically occurring Ophrys species. Ophrys lupercalis, Ophrys bilunulata, and Ophrys fabrella grow sympatrically and bloom consecutively on Majorca and are pollinated by three species of Andrena. We investigated variation of phenotypic and genotypic flower traits, aiming to study the role of the floral odour for reproductive isolation and speciation. Using chemical and electrophysiology (gas chromatography coupled with an electroantennographic detector) methods, we show that the three Ophrys species use the same odour compounds for pollinator attraction, but in different proportions. A comparison of the floral odour bouquets in a multivariate analysis revealed a clear grouping of plants from the same species, although with an overlap between species. A comparison of the same plants using molecular markers gave a contrasting result. Although O. lupercalis and O. fabrella were genetically well separated, plants of O. bilunulata did not form a distinct group but were similar to either O. lupercalis or O. fabrella. Our data indicate gene flow and hybridization to occur between O. bilunulata and O. lupercalis as well as between O. bilunulata and O. fabrella. All plants of O. bilunulata, despite having different genotypes, showed a very similar floral odour. This reflects a strong selective pressure by the pollinating males. The overlap of genotypes of O. bilunulata and O. fabrella supports our hypothesis that O. fabrella diverged from O. bilunulata by scent variation and the attraction of a new pollinator species, Andrena fabrella. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 98 , 439–451.     

Bioactive compounds produced by cyanobacteria

Cyanobacteria produce a large number of compounds with varying bioactivities. Prominent among these are toxins: hepatotoxins such as microcystins and nodularins and neurotoxins such as anatoxins and saxitoxins. Cytotoxicity to tumor cells has been demonstrated for other cyanobacterial products, including 9-deazaadenosine, dolastatin 13 and analogs. A number of compounds in cyanobacteria are inhibitors of proteases — micropeptins, cyanopeptolins, oscillapeptin, microviridin, aeruginosins- and other enzymes, while still other compounds have no recognized biological activities. In general cyclic peptides and depsipeptides are the most common structural types, but a wide variety of other types are also found: linear peptides, guanidines, phosphonates, purines and macrolides. The close similarity or identity in structures between cyanobacterial products and compounds isolated from sponges, tunicates and other marine invertebrates suggests the latter compounds may be derived from dietary or symbiotic blue-green algae.