Myelin basic protein component C1 in increasing concentrations can elicit fusion, aggregation, and fragmentation of myelin-like membranes

Myelin basic protein (MBP) is considered to have a primary role in the formation and maintenance of the myelin sheath. Many studies using artificial vesicle systems of simple lipid composition, and generally small size, have shown that MBP can elicit vesicle fusion, aggregation, or even fragmentation under different conditions. Here, we have studied the effects of increasing concentrations of bovine MBP charge isomer C1 (MBP/C1) on large unilamellar vesicles (LUVs) composed of phosphatidylcholine and phosphatidylserine (92:8 molar ratio), or with a lipid composition similar to that of the myelin membrane in vivo (Cyt-LUVs). Using absorbance spectrophotometry, fluorescence resonance energy transfer, dynamic light scattering and transmission electron microscopy, we have shown that vesicle aggregation and some vesicle fusion occurred upon addition of MBP/C1, and as the molar protein-lipid ratio increased. Fragmentation of Cyt-LUVs was observed at very high protein concentrations. These results showed that the phenomena of vesicle fusion, aggregation, and fragmentation can all be observed in one in vitro system, but were dependent on lipid composition and on the relative proportions of protein and lipid.     

Development and parasitism by Aphelinus certus (Hymenoptera: Aphelinidae), a parasitoid of Aphis glycines (Hemiptera: Aphididae)

Since its introduction in 2000, the soybean aphid (Aphis glycines Matsumura) has been a serious pest of soybean in North America. Currently, insecticide application is the only recommended control method. However, a number of natural enemies have the potential to regulate soybean aphid populations. In 2007, Aphelinus certus Yasnosh, a soybean aphid parasitoid native to Asia, was found in commercial soybean fields in Ontario. This is the first record of this species in North America. To evaluate the potential biological control services provided by A. certus for soybean aphid management, temperature-dependent developmental parameters and functional response to soybean aphid were determined. A. certus is capable of completing its development between temperatures of 15.3 and 30.2°C. The lower thresholds of development for the egg-mummy and mummy-adult life stages were determined to be 9.1 and 11.6°C, respectively. The lethal temperature of development for the egg-mummy and mummy-adult life stages were 29.5 and 31.0°C, respectively. In this temperature range, A. certus did not exhibit temperature-dependent mortality; however, parasitism rate increased with temperature. A. certus exhibited a type II functional response to the soybean aphid.     

Immune cross-reactivity in celiac disease: anti-gliadin antibodies bind to neuronal synapsin I

Celiac disease is an immune-mediated disorder triggered by ingestion of wheat gliadin and related proteins in genetically susceptible individuals. In addition to the characteristic enteropathy, celiac disease is associated with various extraintestinal manifestations, including neurologic complications such as neuropathy, ataxia, seizures, and neurobehavioral changes. The cause of the neurologic manifestations is unknown, but autoimmunity resulting from molecular mimicry between gliadin and nervous system proteins has been proposed to play a role. In this study, we sought to investigate the immune reactivity of the anti-gliadin Ab response toward neural proteins. We characterized the binding of affinity-purified anti-gliadin Abs from immunized animals to brain proteins by one- and two-dimensional gel electrophoresis, immunoblotting, and peptide mass mapping. The major immunoreactive protein was identified as synapsin I. Anti-gliadin Abs from patients with celiac disease also bound to the protein. Such cross-reactivity may provide clues into the pathogenic mechanism of the neurologic deficits that are associated with gluten sensitivity.     

Ironing out the wrinkles of neutrophil phagocytosis

Though phagocytosis of microbes by professional phagocytes such as neutrophils is crucial for the survival of the host, it is still unclear how the apparent 'stretching' of the plasma membrane is achieved. Microscopically, pseudopod extension, particulate engulfment and phagosome closure all require seemingly large expansions of the cell surface area. Although actual membrane stretching can be ruled out on the basis of physical properties of lipid bilayers, the addition of new membrane from within the cell, either by exocytosis or phagosomal fusion with endoplasmic reticulum membrane, might provide an explanation. However, these events do not seem to have major roles during phagocytosis by neutrophils. Instead, neutrophils might use a more primitive mechanism, that is, the unfolding of surface membrane wrinkles, to provide the additional membrane for phagocytosis. Here, we briefly discuss why membrane unwrinkling provides a feasible hypothesis for membrane expansion during neutrophil phagocytosis, and suggest a potential molecular mechanism for neutrophil control over membrane surface wrinkles, and the potential signalling route.