Mode of interaction of polyoxyethyleneglycol detergents with membrane proteins

Binding of dodecyloctaethyleneglycol monoether (C12E3) and purified Triton X-100 to various integral membrane proteins was studied by chromatographic procedures. Binding capacity decreased in the following order: bovine rhodopsin greater than photochemical reaction center greater than sarcoplasmic reticulum Ca2+-ATPase. The detergents were bound in different amounts to the proteins and less than corresponding to the aggregation number of the pure micelles. Appreciable binding of C12E8 to Ca2+-ATPase was observed far below the critical micelle concentration, consistent with interaction of the membrane protein with non-micellar detergent. Model calculations indicate that the detergents cannot combine with the membrane proteins, forming an oblate ring similar to that of pure detergent micelles, such as has been previously proposed for e.g. cytochrome b5 [Robinson and Tanford (1975) Biochemistry, 14, 365-378]. Other arrangements (prolate and monolayer rings), in which all detergent molecules are in contact with the protein, are considered as alternatives for covering the hydrophobic surface of the membrane protein with a continuous layer of detergent.     

Prolonged increase of corticosterone secretion by chronic social stress does not necessarily impair immune functions.

The influence of a chronic social stress upon immunity was investigated in Wistar rats, submitted for four weeks to two different behavioral situations, balanced in a factorial design: housing with three females and membership rotation. The combination of these two factor led to adrenal enlargement (43.3%), thymus involution (39.5%) and increased basal corticosterone levels, all indices of activation of the hypothalamic-hypophysis-adrenal axis. However, neither natural killer cell activity, splenocyte reactivity to mitogen nor the rate of spontaneous development of antibodies against Mycoplasma pulmonis, a common pathogen of the respiratory tract, were changed in the endocrine activated animals. Analysis of the data on kinetics of stress at 1, 7 and 28 days after the initial mixing of the animals gave the same results. These data question the immunosuppressant activity usually conferred to corticosteroids, at least when adrenal hyperactivity is induced by chronic environmental stressors.     

Genetic structure and life history are key factors in species distribution models of spiny lobsters

AimWe incorporated genetic structure and life history phase in species distribution models (SDMs) constructed for a widespread spiny lobster, to reveal local adaptations specific to individual subspecies and predict future range shifts under the RCP 8.5 climate change scenario.LocationIndo‐West Pacific.MethodsMaxEnt was used to construct present‐day SDMs for the spiny lobster Panulirus homarus and individually for the three genetically distinct subspecies of which it comprises. SDMs incorporated both sea surface and benthic (seafloor) climate layers to recreate discrete influences of these habitats during the drifting larval and benthic juvenile and adult life history phases. Principle component analysis (PCA) was used to infer environmental variables to which individual subspecies were adapted. SDM projections of present‐day habitat suitability were compared with predictions for the year 2,100, under the RCP 8.5 climate change scenario.ResultsIn the PCA, salinity best explained P. h. megasculptus habitat suitability, compared with current velocity in P. h. rubellus and sea surface temperature in P. h. homarus. Drifting and benthic life history phases were adapted to different combinations of sea surface and benthic environmental variables considered. Highly suitable habitats for benthic phases were spatially enveloped within more extensive sea surface habitats suitable for drifting larvae. SDMs predicted that present‐day highly suitable habitats for P. homarus will decrease by the year 2,100.Main conclusionsIncorporating genetic structure in SDMs showed that individual spiny lobster subspecies had unique adaptations, which could not be resolved in species‐level models. The use of sea surface and benthic climate layers revealed the relative importance of environmental variables during drifting and benthic life history phases. SDMs that included genetic structure and life history were more informative in predictive models of climate change effects.     

Towards an understanding of the role of intrinsic protein disorder on plant adaptation to environmental challenges

Intrinsic protein disorder is an interesting structural feature where fully functional proteins lack a three-dimensional structure in solution. In this work, we estimated the relative content of intrinsic protein disorder in 96 plant proteomes including monocots and eudicots. In this analysis, we found variation in the relative abundance of intrinsic protein disorder among these major clades; the relative level of disorder is higher in monocots than eudicots. In turn, there is an inverse relationship between the degree of intrinsic protein disorder and protein length, with smaller proteins being more disordered. The relative abundance of amino acids depends on intrinsic disorder and also varies among clades. Within the nucleus, intrinsically disordered proteins are more abundant than ordered proteins. Intrinsically disordered proteins are specialized in regulatory functions, nucleic acid binding, RNA processing, and in response to environmental stimuli. The implications of this on plants’ responses to their environment are discussed.     

Hippocampal Neuroligin-2 Overexpression Leads to Reduced Aggression and Inhibited Novelty Reactivity in Rats

Disturbances of the excitation/inhibition (E/I) balance in the brain were recently suggested as potential factors underlying disorders like autism and schizophrenia resulting in associated behavioral alterations including changes in social and emotional behavior as well as abnormal aggression. Neuronal cell adhesion molecules (nCAMs) and mutations in these genes were found to be strongly implicated in the pathophysiology of these disorders. Neuroligin2 (nlgn2) is a postsynaptic cell adhesion molecule, which is predominantly expressed at inhibitory synapses and required for synapse specification and stabilization. Changes in the expression of nlgn2 were shown to result in alterations of social behavior as well as altered inhibitory synaptic transmission, hence modifying the E/I balance. In our study, we focused on the role of nlgn2 in the dorsal hippocampus in the regulation of emotional and social behaviors. To this purpose, we injected an AAV construct overexpressing nlgn2 in the hippocampus of rats and investigated the effects on behavior and on markers for the E/I ratio. We could show an increase in GAD65, a GABA-synthesizing protein in neuronal terminals, and furthermore, reduced exploration of novel stimuli and less offensive behavior. Our data suggest nlgn2 in the hippocampus to be strongly implicated in maintaining the E/I balance in the brain and thereby modulating social and emotional behavior.     

The NOMEGA gene required for female gametophyte development encodes the putative APC6/CDC16 component of the Anaphase Promoting Complex in Arabidopsis

Development of the female gametophyte involves several rounds of nuclear divisions during which nuclei are rearranged and finally cellularized to form a mature seven-celled embryo sac. During these nuclear divisions, key proteins involved in the cell cycle need to be degraded quickly in order to facilitate both the metaphase-anaphase transition stage and late anaphase. Here, we report the characterization of an Arabidopsis mutant nomega, which results in arrest of the embryo sac development at the two-nucleate stage. The NOMEGA gene product shows high homology to the APC6/cell division cycle (CDC)16 subunit of the Anaphase Promoting Complex/Cyclosome (APC/C). The phenotype of the nomega mutant is quite different from that of the hobbit mutant, which had suggested a role for the plant APC/C in auxin signalling. We show that nomega mutant embryo sacs are unable to degrade Cyclin B, an important APC/C substrate, providing further evidence of a role for the NOMEGA gene product and the plant APC/C in cell cycle progression during gametophyte development.     

Effects of Adenovirus Type 5 E1A Isoforms on Viral Replication in Arrested Human Cells

Human adenovirus has evolved to infect and replicate in terminally differentiated human epithelial cells, predominantly those within the airway, the gut, or the eye. To overcome the block to viral DNA replication present in these cells, the virus expresses the Early 1A proteins (E1A). These immediate early proteins drive cells into S-phase and induce expression of all other viral early genes. During infection, several E1A isoforms are expressed with proteins of 289, 243, 217, 171, and 55 residues being present for human adenovirus type 5. Here we examine the contribution that the two largest E1A isoforms make to the viral life cycle in growth-arrested normal human fibroblasts. Viruses that express E1A289R were found to replicate better than those that do not express this isoform. Importantly, induction of several viral genes was delayed in a virus expressing E1A243R, with several viral structural proteins undetectable by western blot. We also highlight the changes in E1A isoforms detected during the course of viral infection. Furthermore, we show that viral DNA replication occurs more efficiently, leading to higher number of viral genomes in cells infected with viruses that express E1A289R. Finally, induction of S-phase specific genes differs between viruses expressing different E1A isoforms, with those having E1A289R leading to, generally, earlier activation of these genes. Overall, we provide an overview of adenovirus replication using modern molecular biology approaches and further insights into the contribution that E1A isoforms make to the life cycle of human adenovirus in arrested human fibroblasts.     

A novel GAA-repeat-expansion-based mouse model of Friedreich’s ataxia

Friedreich’s ataxia (FRDA) is an autosomal recessive neurodegenerative disorder caused by a GAA repeat expansion mutation within intron 1 of the FXN gene, resulting in reduced levels of frataxin protein. We have previously reported the generation of human FXN yeast artificial chromosome (YAC) transgenic FRDA mouse models containing 90–190 GAA repeats, but the presence of multiple GAA repeats within these mice is considered suboptimal. We now describe the cellular, molecular and behavioural characterisation of a newly developed YAC transgenic FRDA mouse model, designated YG8sR, which we have shown by DNA sequencing to contain a single pure GAA repeat expansion. The founder YG8sR mouse contained 120 GAA repeats but, due to intergenerational expansion, we have now established a colony of YG8sR mice that contain ~200 GAA repeats. We show that YG8sR mice have a single copy of the FXN transgene, which is integrated at a single site as confirmed by fluorescence in situ hybridisation (FISH) analysis of metaphase and interphase chromosomes. We have identified significant behavioural deficits, together with a degree of glucose intolerance and insulin hypersensitivity, in YG8sR FRDA mice compared with control Y47R and wild-type (WT) mice. We have also detected increased somatic GAA repeat instability in the brain and cerebellum of YG8sR mice, together with significantly reduced expression of FXN, FAST-1 and frataxin, and reduced aconitase activity, compared with Y47R mice. Furthermore, we have confirmed the presence of pathological vacuoles within neurons of the dorsal root ganglia (DRG) of YG8sR mice. These novel GAA-repeat-expansion-based YAC transgenic FRDA mice, which exhibit progressive FRDA-like pathology, represent an excellent model for the investigation of FRDA disease mechanisms and therapy.KEY WORDS: GAA repeat, Friedreich’s ataxia, FRDA, YG8sR, Mouse model