Knockdown of the Sodium-Dependent Phosphate Co-Transporter 2b (NPT2b) Suppresses Lung Tumorigenesis

The sodium-dependent phosphate co-transporter 2b (NPT2b) plays an important role in maintaining phosphate homeostasis. In previous studies, we have shown that high dietary inorganic phosphate (Pi) consumption in mice stimulated lung tumorigenesis and increased NPT2b expression. NPT2b has also been found to be highly expressed in human lung cancer tissues. The association of high expression of NPT2b in the lung with poor prognosis in oncogenic lung diseases prompted us to test whether knockdown of NPT2b may regulate lung cancer growth. To address this issue, aerosols that contained small interfering RNA (siRNA) directed against NPT2b (siNPT2b) were delivered into the lungs of K-ras ^LA1 mice, which constitute a murine model reflecting human lung cancer. Our results clearly showed that repeated aerosol delivery of siNPT2b successfully suppressed lung cancer growth and decreased cancer cell proliferation and angiogenesis, while facilitating apoptosis. These results strongly suggest that NPT2b plays a role lung tumorigenesis and represents a novel target for lung cancer therapy.     

Multi-Scale Assessment of Male Northern Yellow Bat Roost Selection

Knowledge of roost selection by northern yellow bats (Lasiurus intermedius) is limited to a small number of known roost locations. Yet knowledge of basic life history is fundamental to understanding past response to anthropogenic change and to predict how species will respond to future environmental change. Therefore, we examined male northern yellow bat roost selection on 2 Georgia, USA, barrier islands with different disturbance histories. Sapelo Island has a history of extensive disturbance and is dominated by pine (Pinus spp.) forests; Little Saint Simons Island has a limited disturbance history with maritime oak (Quercus spp.) forest as the dominant cover type. From March–July 2012 and 2013, we radio-tracked 35 adult male northern yellow bats to diurnal roosts and modeled roost characteristics at the plot and landscape scales. We located 387 roosts, of which 95% were in Spanish moss (Tillandsia usneoides) hanging in hardwood trees. On both islands, bats selected roost trees with larger diameters than surrounding trees and selected roost locations with greater open flight space (i.e., low midstory clutter) underneath. Roosts were located farther from open areas on Sapelo and closer to fresh water on Little Saint Simons compared to random locations. Lower availability of hardwood forest on Sapelo may have resulted in small-scale roost site selection (i.e., plot level) despite potential increased costs of commuting to water and open areas for foraging. In contrast, greater availability of hardwood forest on Little Saint Simons likely allowed selection of roosts closer to fresh water, which provides foraging and drinking opportunities. Our results indicate that mature hardwood trees in areas with low midstory clutter are important in male northern yellow bat roost selection, but landscape-level features have varying influences on roost selection, likely as a result of differences in disturbance history. Therefore, management will differ depending on the landscape context. Further research is needed to examine roost selection by females, which may have different habitat requirements. © 2020 The Wildlife Society.     

Anthropogenic and Natural Disturbance Differentially Affect Sagebrush Bird Habitat Use

North American sagebrush (Artemisia spp.)-obligate birds are experiencing steep population declines due in part to increased disturbance, mainly human-caused, across their range. At the eastern edge of the sagebrush steppe, this issue may potentially be exacerbated because of natural disturbance by black-tailed prairie dogs (Cynomys ludovicianus). Our goal was to compare local and landscape models of habitat use by greater sage-grouse (Centrocercus urophasianus), Brewer's sparrow (Spizella breweri), and sage thrasher (Oreoscoptes montanus) with models including effects of natural (i.e., prairie dog) and anthropogenic disturbance. We used a combination of field data collection, and state and national datasets for the Thunder Basin National Grassland, eastern Wyoming, USA, to understand the factors that influence lek attendance by sage-grouse and habitat use by 2 passerines in this system. For all 3 species, models including big sagebrush (Artemisia tridentata) cover at local and landscape scales were the most competitive among univariate models, supporting the paradigm that sagebrush is key for these species. Models including anthropogenic disturbance (well density, road density) explained more variation than models of prairie dog disturbance alone for 2 of the 3 species, but long-term disturbance by prairie dogs did reduce abundance of Brewer's sparrows. Although long-term prairie dog disturbance has the potential to reduce sagebrush cover for sagebrush-obligate birds, such events are likely rare because outbreaks of plague (Yersina pestis) and lethal control on borders with private land reduce prairie dog disturbance. Conversely, anthropogenic disturbance is slated to increase in this system, suggesting potentially accelerated declines for sagebrush birds into the future. © 2020 The Wildlife Society.     

Saturated phospholipids are required for nano- to micron-size transformation of cholesterol-containing liposomes upon QS21 addition

Abstract

Liposomes containing cholesterol and monophosphoryl lipid A (such as ALFQ and AS01B) are vaccine adjuvants. During construction of the formulations, addition of QS21 to nano-size (50–100?nm) liposomes resulted in extremely large (up to ～30 µm) liposomes in ALFQ, but AS01B liposomes remained small nano-vesicles. Here, we show that saturation of phospholipid chains is essential for production of large liposomes by QS21.     

Isoform-specific roles of the GTPase activating protein Nadrin in cytoskeletal reorganization of platelets

Cytoskeletal reorganization of activated platelets plays a crucial role in hemostasis and thrombosis and implies activation of Rho GTPases. Rho GTPases are important regulators of cytoskeletal dynamics and function as molecular switches that cycle between an inactive and an active state. They are regulated by GTPase activating proteins (GAPs) that stimulate GTP hydrolysis to terminate Rho signaling. The regulation of Rho GTPases in platelets is not explored. A detailed characterization of Rho regulation is necessary to understand activation and inactivation of Rho GTPases critical for platelet activation and aggregation. Nadrin is a RhoGAP regulating cytoplasmic protein explored in the central nervous system. Five Nadrin isoforms are known that share a unique GAP domain, a serine/threonine/proline-rich domain, a SH3-binding motif and an N-terminal BAR domain but differ in their C-terminus. Here we identified Nadrin in platelets where it co-localizes to actin-rich regions and Rho GTPases. Different Nadrin isoforms selectively regulate Rho GTPases (RhoA, Cdc42 and Rac1) and cytoskeletal reorganization suggesting that – beside the GAP domain – the C-terminus of Nadrin determines Rho specificity and influences cell physiology. Furthermore, Nadrin controls RhoA-mediated stress fibre and focal adhesion formation. Spreading experiments on fibrinogen revealed strongly reduced cell adhesion upon Nadrin overexpression. Unexpectedly, the Nadrin BAR domain controls Nadrin-GAP activity and acts as a guidance domain to direct this GAP to its substrate at the plasma membrane. Our results suggest a critical role for Nadrin in the regulation of RhoA, Cdc42 and Rac1 in platelets and thus for platelet adhesion and aggregation.     

Role of G‐proteins in the effects of leptin on pedunculopontine nucleus neurons

The pedunculopontine nucleus (PPN), the cholinergic arm of the reticular activating system, regulates waking and rapid eye movement sleep. Here, we demonstrate immunohistochemical labeling of the leptin receptor signaling isoform in PPN neurons, and investigated the effects of G‐protein modulation and the leptin triple antagonist (TA) on the action of leptin in the PPN. Whole‐cell patch clamp recordings were performed in rat brainstem slices from 9 to 17 day old pups. Previous results showed that leptin caused a partial blockade of sodium (I_Na) and h‐current (I_H) in PPN neurons. TA (100 nM) reduced the blockade of I_Na (~ 50% reduction) and I_H (~ 93% reduction) caused by leptin. Intracellular guanosine 5′‐[β‐thio]diphosphate trilithium salt (a G‐protein inhibitor) significantly reduced the effect of leptin on I_Na(~ 60% reduction) but not on I_H (~ 25% reduction). Intracellular GTPγS (a G‐protein activator) reduced the effect of leptin on both I_Na (~ 80% reduction) and I_H (~ 90% reduction). These results suggest that the effects of leptin on the intrinsic properties of PPN neurons are leptin receptor‐ and G‐protein dependent. We also found that leptin enhanced NMDA receptor‐mediated responses in single neurons and in the PPN population as a whole, an effect blocked by TA. These experiments further strengthen the association between leptin dysregulation and sleep disturbances.

     

Sustained Protein Kinase D Activation Mediates Respiratory Syncytial Virus-Induced Airway Barrier Disruption

Understanding the regulation of airway epithelial barrier function is a new frontier in asthma and respiratory viral infections. Despite recent progress, little is known about how respiratory syncytial virus (RSV) acts at mucosal sites, and very little is known about its ability to influence airway epithelial barrier function. Here, we studied the effect of RSV infection on the airway epithelial barrier using model epithelia. 16HBE14o- bronchial epithelial cells were grown on Transwell inserts and infected with RSV strain A2. We analyzed (i) epithelial apical junction complex (AJC) function, measuring transepithelial electrical resistance (TEER) and permeability to fluorescein isothiocyanate (FITC)-conjugated dextran, and (ii) AJC structure using immunofluorescent staining. Cells were pretreated or not with protein kinase D (PKD) inhibitors. UV-irradiated RSV served as a negative control. RSV infection led to a significant reduction in TEER and increase in permeability. Additionally it caused disruption of the AJC and remodeling of the apical actin cytoskeleton. Pretreatment with two structurally unrelated PKD inhibitors markedly attenuated RSV-induced effects. RSV induced phosphorylation of the actin binding protein cortactin in a PKD-dependent manner. UV-inactivated RSV had no effect on AJC function or structure. Our results suggest that RSV-induced airway epithelial barrier disruption involves PKD-dependent actin cytoskeletal remodeling, possibly dependent on cortactin activation. Defining the mechanisms by which RSV disrupts epithelial structure and function should enhance our understanding of the association between respiratory viral infections, airway inflammation, and allergen sensitization. Impaired barrier function may open a potential new therapeutic target for RSV-mediated lung diseases.     

Book review

The Oribatid Genera of the World von J. BALOGH, Verlag Akademiai Kiado, Budapest 1972. 188 S., 71 Tafeln. Preis 42.‐ DM.