Neto2 Interacts with the Scaffolding Protein GRIP and Regulates Synaptic Abundance of Kainate Receptors

Kainate receptors (KARs) are a class of ionotropic glutamate receptors that are expressed throughout the central nervous system. The function and subcellular localization of KARs are tightly regulated by accessory proteins. We have previously identified the single-pass transmembrane proteins, Neto1 and Neto2, to be associated with native KARs. In the hippocampus, Neto1, but not Neto2, controls the abundance and modulates the kinetics of postsynaptic KARs. Here we evaluated whether Neto2 regulates synaptic KAR levels in the cerebellum where Neto1 expression is limited to the deep cerebellar nuclei. In the cerebellum, where Neto2 is present abundantly, we found a ∼40% decrease in GluK2-KARs at the postsynaptic density (PSD) of Neto2-null mice. No change, however, was observed in total level of GluK2-KARs, thereby suggesting a critical role of Neto2 on the synaptic localization of cerebellar KARs. The presence of a putative class II PDZ binding motif on Neto2 led us to also investigate whether it interacts with PDZ domain-containing proteins previously implicated in regulating synaptic abundance of KARs. We identified a PDZ-dependent interaction between Neto2 and the scaffolding protein GRIP. Furthermore, coexpression of Neto2 significantly increased the amount of GRIP associated with GluK2, suggesting that Neto2 may promote and/or stabilize GluK2:GRIP interactions. Our results demonstrate that Neto2, like Neto1, is an important auxiliary protein for modulating the synaptic levels of KARs. Moreover, we propose that the interactions of Neto1/2 with various scaffolding proteins is a critical mechanism by which KARs are stabilized at diverse synapses.     

Remote Sensing of Climatic Anomalies and West Nile Virus Incidence in the Northern Great Plains of the United States

The northern Great Plains (NGP) of the United States has been a hotspot of West Nile virus (WNV) incidence since 2002. Mosquito ecology and the transmission of vector-borne disease are influenced by multiple environmental factors, and climatic variability is an important driver of inter-annual variation in WNV transmission risk. This study applied multiple environmental predictors including land surface temperature (LST), the normalized difference vegetation index (NDVI) and actual evapotranspiration (ETa) derived from Moderate-Resolution Imaging Spectroradiometer (MODIS) products to establish prediction models for WNV risk in the NGP. These environmental metrics are sensitive to seasonal and inter-annual fluctuations in temperature and precipitation, and are hypothesized to influence mosquito population dynamics and WNV transmission. Non-linear generalized additive models (GAMs) were used to evaluate the influences of deviations of cumulative LST, NDVI, and ETa on inter-annual variations of WNV incidence from 2004–2010. The models were sensitive to the timing of spring green up (measured with NDVI), temperature variability in early spring and summer (measured with LST), and moisture availability from late spring through early summer (measured with ETa), highlighting seasonal changes in the influences of climatic fluctuations on WNV transmission. Predictions based on these variables indicated a low WNV risk across the NGP in 2011, which is concordant with the low case reports in this year. Environmental monitoring using remote-sensed data can contribute to surveillance of WNV risk and prediction of future WNV outbreaks in space and time.     

Allium cepa L. Cultivars from Four Continents Compared by Flow Cytometry show Nuclear DNA Constancy

In 1965 Van't Hof estimated the nuclear DNA amount of an unidentifiedAllium cepa L. cultivar as 2C = 33.55 pg (Experimental CellResearch39: 8–58). This value has been adopted by commonusage as the main calibration standard for angiosperm DNA C-valueestimations. However, different cultivars have been used whileassuming species DNA C-value constancy. Surprisingly this assumptionhas never been tested. A. cepa is an outbreeder with telomericheterochromatic segments, so intraspecific variation in C-value,possibly correlated with environmental factors as seen in Zeamays L., might be expected. We used laser flow cytometry tocompare nuclear DNA amounts in roots of six A. cepa cultivarsused as calibration standards or from different environments.Tissues from one cultivar, or similar volumes of tissue fromtwo cultivars, were run and the variance between nuclei in 2Cpeaks compared. Only one shoulderless 2C peak was seen for allpairs of co-chopped cultivars. Thus, no large differences inC-value between cultivars from different environments were found.Moreover, comparing cultivars run singly or as pairs showedno evidence for increased variation in 2C peaks in the latter,and hence of critical differences in DNA amounts between ‘AilsaCraig’ and another cultivar. Such variation was insufficientto make their use as alternative calibration standards, or thepractice of imputing Van't Hof's original C-value estimate tothem, unacceptable for most practical purposes. Given the mechanismsknown which can generate genome size variation, the degree ofconstancy in DNA C-value found seems remarkable. Copyright 2000Annals of Botany Company Allium cepa, onion cultivars, calibration standards, DNA C-value constancy, flow cytometry     

Architectural specialization of the intrinsic thoracic limb musculature of the American badger (Taxidea taxus)

Evaluation of the relationships between muscle structure and digging function in fossorial species is limited. Badgers and other fossorial specialists are expected to have massive forelimb muscles with long fascicles capable of substantial shortening for high power and applying high out‐force to the substrate. To explore this hypothesis, we quantified muscle architecture in the thoracic limb of the American badger (Taxidea taxus) and estimated the force, power, and joint torque of its intrinsic musculature in relation to the use of scratch‐digging behavior. Architectural properties measured were muscle mass, belly length, fascicle length, pennation angle, and physiological cross‐sectional area. Badgers possess hypertrophied shoulder flexors/humeral retractors, elbow extensors, and digital flexors. The triceps brachii is particularly massive and has long fascicles with little pennation, muscle architecture consistent with substantial shortening capability, and high power. A unique feature of badgers is that, in addition to elbow joint extension, two biarticular heads (long and medial) of the triceps are capable of applying high torques to the shoulder joint to facilitate retraction of the forelimb throughout the power stroke. The massive and complex digital flexors show relatively greater pennation and shorter fascicle lengths than the triceps brachii, as well as compartmentalization of muscle heads to accentuate both force production and range of shortening during flexion of the carpus and digits. Muscles of most functional groups exhibit some degree of specialization for high force production and are important for stabilizing the shoulder, elbow, and carpal joints against high limb forces generated during powerful digging motions. Overall, our findings support the hypothesis and indicate that forelimb muscle architecture is consistent with specializations for scratch‐digging. Quantified muscle properties in the American badger serve as a comparator to evaluate the range of diversity in muscle structure and contractile function that exists in mammals specialized for fossorial habits. J. Morphol. 2013. © 2012 Wiley Periodicals, Inc.     

Septum volume and food‐storing behavior are related in parids

The hippocampal formation (HF) of food‐storing birds is larger than non‐storing species, and the size of the HF in food‐storing Black‐Capped Chickadees (Poecile atricapillus) varies seasonally. We examined whether the volume of the septum, a medial forebrain structure that shares reciprocal connections with the HF, demonstrates the same species and seasonal variation as has been shown in the HF. We compared septum volume in three parid species; non‐storing Blue Tits (Parus caeruleus) and Great Tits (Parus major), and food‐storing Black‐Capped Chickadees. We found the relative septum volume to be larger in chickadees than in the non‐storing species. We also compared septum and nucleus of the diagonal band (NDB) volume of Black‐Capped Chickadees at different times of the year. We found that the relative septum volume varies seasonally in food‐storing birds. The volume of the NDB does not vary seasonally. Due to the observed species and seasonal variation, the septum, like the hippocampal formation of food‐storing birds, may be specialized for some aspects of food‐storing and spatial memory. © 2002 Wiley Periodicals, Inc. J Neurobiol 51: 215–222, 2002     

Ultrastructural visualization of the internalization of low density lipoprotein by human placental cells

Low density lipoproteins (LDL) were conjugated to colloidal gold to visualize the route for internalization of LDL in the cultured cells of human term placenta. Cells were obtained from placental villi (caesarian section) by a standard trypsin-DNase dispersion method followed in some cases by a Percoll gradient centrifugation step. Employing electron microscopy it was observed that after 3 days of culture, cells obtained by trypsin-DNase dispersion were a mixture of macrophages, mononucleated cells and large multinucleated cells. When the cells were incubated for 3 days after the Percoll purification, essentially multinucleated cells identical to the syncytiotrophoblast were present. The number of LDL receptor was increased by preincubation in medium with lipoprotein depleted serum. In binding experiments cells incubated at 4 degrees C for 2 h with medium containing gold LDL conjugates showed gold LDL attached to the plasma membrane without characteristic localization. After incubation with gold LDL at 37 degrees C for various times, the three cellular types showed ligand internalization. Gold LDL endocytosis involved first coated pits but also uncoated plasmalemmal invaginations. Then gold LDL was further observed in coated and non coated vesicles, smooth walled endosomes, multivesicular bodies and tubular vesicles. Lastly free gold particles were observed in lysosome like dense bodies. These results prove the internalization of gold LDL conjugates by human cultured placental cells, particularly by syncytiotrophoblast like multinucleated cells. This accumulation of LDL (the major cholesterol carrying protein in humans) is recognised to be responsible for the exogenous cholesterol supply indispensable to the progesterone biosynthesis and cellular growth of the placenta.     

Galectin 9 is the sugar-regulated urate transporter/channel UAT

UAT, also designated galectin 9, is a multifunctional protein that can function as a urate channel/transporter, a regulator of thymocyte-epithelial cell interactions, a tumor antigen, an eosinophil chemotactic factor, and a mediator of apoptosis. We review the evidence that UAT is a transmembrane protein that transports urate, describe our molecular model for this protein, and discuss the evidence from epitope tag and lipid bilayer studies that support this model of the transporter. The properties of recombinant UAT are compared with those of urate transport into membrane vesicles derived from proximal tubule cells in rat kidney cortex. In addition, we review channel functions predicted by our molecular model that resulted in the novel finding that the urate channel activity is regulated by sugars and adenosine. Finally, the presence and possible functions of at least 4 isoforms of UAT and a closely related gene hUAT2 are discussed. Published in 2004.