Rab11 Regulates the Mast Cell Exocytic Response

Stimulated exocytic events provide a means for physiological communication and are a hallmark of the mast cell‐mediated allergic response. In mast cells these processes are triggered by antigen crosslinking of IgE bound to its high‐affinity receptor, Fc?RI, on the cell surface. Here we use the endosomal v‐SNARE VAMP8, and the lysosomal hydrolase β‐hexosaminidase (β‐Hex), each C‐terminally fused to super‐ecliptic pHluorin, to monitor stimulated exocytosis. Using these pHluorin‐tagged constructs, we monitor stimulated exocytosis by fluorimetry and visualize individual exocytic events with total internal reflection (TIRF) microscopy. Similar to constitutive recycling endosome (RE) trafficking, we find that stimulated RE exocytosis, monitored by VAMP8, is attenuated by expression of dominant negative (S25N) Rab11. Stimulated β‐Hex exocytosis is also reduced in the presence of S25N Rab11, suggesting that expression of this mutant broadly impacts exocytosis. Interestingly, pretreatment with inhibitors of actin polymerization, cytochalasin D or latrunculin A, substantially restores both RE and lysosome exocytosis in cells expressing S25N Rab11. Conversely, stabilizing F‐actin with jasplakinolide inhibits antigen‐stimulated exocytosis but is not additive with S25N Rab11‐mediated inhibition, suggesting that these reagents inhibit related processes. Together, our results suggest that Rab11 participates in the regulation necessary for depolymerization of the actin cytoskeleton during stimulated exocytosis in mast cells.      

Dopamine complexes of iron in the etiology and pathogenesis of Parkinson's disease

Parkinson’s disease (PD) is the second most common neurodegenerative disease after Alzheimers. The main pathological hallmark of Parkinson’s is the deterioration and death of neurons that produce the neurotransmitter dopamine. Much of the neuronal damage takes place in the substantia nigra, a small region of the midbrain that contains the cell bodies of neurons that produce dopamine. The deterioration and death of dopaminergic neurons are directly associated with misfolding and aggregation of proteins, principally α-synuclein, that are natively unfolded. Present also in the substantia nigra is an unusually high concentration of vestigial iron. Protein misfolding in non-genetic (sporadic) cases of PD has been associated with reactive oxygen species formed as products of O₂ reduction by the combination of dopamine and iron. Combinations of Fe³⁺, dopamine hydrochloride (DA^H+Cl), and various ancillary ligands have been studied as a function of pH in aqueous solution to determine the optimum pH for complex formation. With ancillary ligands (L₄) derived from nitrilotriacetic acid and ethylenediamine diacetic acid spectral changes are consistent with the formation of L₄Fe(DA^H+) species that reach a maximum concentration at pH 7.2. With edta as the ancillary ligand, spectral features at pH 7 resemble those of Fe³⁺-catecholate complexes that contain catecholate ligands bonded through a single oxygen. This demonstrates the ability of the dopamine catechol functionality to penetrate the coordination sphere of even exceptionally stable iron chelates.     

The Evolution of RecD Outside of the RecBCD Complex

The common understanding of the function of RecD, as derived predominantly from studies in Escherichia coli, is that RecD is one of three enzymes in the RecBCD double-stranded break repair DNA recombination complex. However, comparative genomics has revealed that many organisms possess a recD gene even though the other members of the complex, recB and recC, are not present. Further, bioinformatic analyses have shown that there is substantial sequence dissimilarity between recD genes associated with recB and recC (recD1), and those that are not associated with recBC (recD2). Deinococcus radiodurans, known for its extraordinary DNA repair capability, is one such organism that does not possess either recB or recC, and yet does possess a recD gene. The recD of D. radiodurans was deleted and this mutant was shown to have a capacity to repair double-stranded DNA breaks equivalent to wild-type. The phylogenetic history of recD was studied using a dataset of 120 recD genes from 91 fully sequenced species. The analysis focused upon the role of gene duplication and functional genomic context in the evolution of recD2, which appears to have undergone numerous independent events resulting in duplicate recD2 genes. The role of RecD as part of the RecBCD complex appears to have a divergence from an earlier ancestral RecD function still preserved in many species including D. radiodurans.     

The importance of temperate woodland in travelling stock reserves for vertebrate biodiversity conservation

Summary Travelling stock reserves have well recognised and important commercial, cultural and other values in the pastoral and agricultural regions of Australia, but their conservation values remain poorly known. In general, many areas of woodlands within travelling stock reserves have not been subjected to the same high levels of degradation pressure as similar temperate woodlands on private land. In this study, we compared several measures of vertebrate biota in 217 permanent field sites located in travelling stock reserves and woodland remnants located almost exclusively on private land in the Murray Riverina and South West Slopes bioregions in southern New South Wales. We found that in comparison with temperate woodland remnants on private land, temperate woodland in travelling stock reserves tended to support more species of birds, more species of declining birds, and a greater abundance of arboreal marsupials. Temperate woodland in travelling stock reserves was more likely to be occupied by particular individual species of birds of conservation concern. However, such tenure differences were not consistent between bioregions. For example, the Rufous Whistler (Pachycephala rufiventris) and the Red‐capped Robin (Petroica goodenovii ) were significantly more likely to occupy temperate woodland in travelling stock reserves than temperate woodland on private land in the Murray Riverina but such effects were not apparent in the South West Slopes. Similarly, while the Grey‐crowned Babbler (Pomatostomus temporalis) was significantly more likely to occupy temperate woodland in travelling stock reserve sites in the South West Slopes, we found the opposite effect in Murray Riverina. We demonstrated that travelling stock reserves have important conservation values for some taxa and individual species. Because of the paucity of large ecological reserves in the Murray Riverina and South West Slopes bioregions, temperate woodlands located in travelling stock reserves should be considered as an important resource that contributes to a portfolio of vegetation assets in formerly woodland‐dominated, but now extensively cleared, agricultural landscapes.     

Referential alarm calling elicits future vigilance in a host of an avian brood parasite

Yellow warblers (Setophaga petechia) use referential ‘seet’ calls to warn mates of brood parasitic brown-headed cowbirds (Molothrus ater). In response to seet calls during the day, female warblers swiftly move to sit tightly on their nests, which may prevent parasitism by physically blocking female cowbirds from inspecting and laying in the nest. However, cowbirds lay their eggs just prior to sunrise, not during daytime. We experimentally tested whether female warblers, warned by seet calls on one day, extend their anti-parasitic responses into the future by engaging in vigilance at sunrise on the next day, when parasitism may occur. As predicted, daytime seet call playbacks caused female warblers to leave their nests less often on the following morning, relative to playbacks of both their generic anti-predator calls and silent controls. Thus, referential calls do not only convey the identity or the type of threat at present but also elicit vigilance in the future to provide protection from threats during periods of heightened vulnerability.