Animal toxins that modulate the activity of voltage-gated sodium (Na) channels are broadly divided into two categories-pore blockers and gating modifiers. The pore blockers tetrodotoxin (TTX) and saxitoxin (STX) are responsible for puffer fish and shellfish poisoning in humans, respectively. Here, we present structures of the insect Na channel NaPaS bound to a gating modifier toxin Dc1a at 2.8 angstrom-resolution and in the presence of TTX or STX at 2.6-Å and 3.2-Å resolution, respectively. Dc1a inserts into the cleft between VSD and the pore of NaPaS, making key contacts with both domains. The structures with bound TTX or STX reveal the molecular details for the specific blockade of Na access to the selectivity filter from the extracellular side by these guanidinium toxins. The structures shed light on structure-based development of Na channel drugs.

discovered by Ockner et al. in 1972 ( 2 ) and was originally named Z-protein. Since that time, there has been an explosive growth in information regarding the role of L-FABP in cellular homeostasis. While FABPs are present in many tissues, such as heart, brain, intestinal, skin, adipose, muscle, epidermal, ileal, myelin, and testis, L-FABP is found in abundance in hepatocytes where it accounts for ‫ف‬ 2% of the total cellular protein. Although L-FABP is abundant in the liver, it also is present in tissues such as murine alveolar macrophages ( 3 ), kidney ( 4 ), and intestine ( 5 ).L-FABP is made up of 127 amino acids that compose 10 antiparallel ␤ -strands. These stands are organized into two fi ve-stranded ␤ -sheets and two ␣ -helices. The two ␣ -helices are hypothesized to function as a portal that controls entry and release of ligands from the binding pocket created by the ␤ -strands ( 6 ). A large interior water-fi lled cavity forms the confi nes of the ␤ -strands, which serve as the hydrophobic ligand-binding site. L-FABP is able to bind and translocate many lipophilic substrates throughout the cytosol. Some of these substrates include long-chain fatty acids ( 7-9 ), bile acids ( 10 ), eicosanoids ( 11 ), and hypolipidemic drugs ( 12 ). Transfer of these ligands from L-FABP to membranes is thought to occur by a diffusive process; i.e., the ligand fi rst dissociates from the binding pocket and then diffuses to its site of action, while transfer of ligands from other FABPs, such as I-FABP, is thought to occur by a direct collisional interaction ( 13 ). It seems that L-FABP also plays a role in transferring bound ligands into the nucleus. These ligands could activate the peroxisome proliferator-activated receptor ␣ nuclear receptors and

The presence of cysteine and methionine groups together with an ability to bind long-chain fatty acid (LCFA) oxidation products makes liver fatty acid binding protein (L-FABP) an attractive candidate against hepatocellular oxidative stress. In this report, we show that pharmacological treatment directed at modulating L-FABP level affected hepatocellular oxidant status. L-FABP expressing 1548-hepatoma cells, treated with dexamethasone or clofibrate, decreased and increased intracellular L-FABP levels, respectively. Oxidative stress was induced by H2O2 incubation or hypoxia-reoxygenation. The fluorescent marker, dichlorofluorescein (DCF), was employed to measure intracellular reactive oxygen species (ROS). Hepatocellular damage was assessed by lactate dehydrogenase (LDH) level. Dexamethasone treatment resulted in a significant increase in DCF fluorescence with higher LDH release compared to control cells. Clofibrate treatment, however, resulted in a significant decrease in both parameters (p<0.05). Drug treatments did not affect cytosolic activities of glutathione peroxidase (GPx), superoxide dismutase (SOD), or catalase suggesting that the differences between treated and control cells may likely be associated with varying L-FABP levels. We conclude that L-FABP may act as an effective endogenous cytoprotectant against hepatocellular oxidative stress.

IgG staining in human vagus nerves; H&E and Na v 1.7 expression in mouse sciatic nerves; tryptic digestion experiments for Hsp1a and Hsp1a-FL; epifluorescence images of sciatic nerves injected with Hsp1a-FL, block, or PBS, and the fluorescence quantification; fresh tissue confocal fluorescence microscopy (PDF) The authors declare the following competing financial interest(s): J.G., P.D.S.F., G.F.K. and T.R. are co-inventors on a Hsp1a-related patent application. S.K. and T.R. are shareholders of Summit Biomedical Imaging, LLC.

A study was conducted to investigate the effect of dietary yeast polysaccharides on some hematologic parameters and intestinal morphology of channel catfish. Channel catfish were fed diets containing yeast polysaccharides at 0 (control), 0.1, 0.2, or 0.3 % for 7 weeks. Each diet was provided to 10 channel catfish specimens (5.82 ± 0.13 g initial weight) replicated 3 times in individual 250 L fiberglass tanks. Some hematologic parameters, leukocyte phagocytic activity, and intestinal morphology were monitored. After 7 weeks of trial, 0.2 % yeast polysaccharides resulted in significantly higher (P < 0.05) monocyte numbers. Furthermore, fish fed 0.2 % yeast polysaccharide diet had higher (P < 0.05) phagocytic rate of leukocyte. And 0.3 % yeast polysaccharide enhanced (P < 0.05) phagocytic index of leukocyte. Histological evaluation showed yeast polysaccharide supplementation increased the height of intestine fold (0.1, 0.2 and 0.3 %) and the thick of muscular layers (0.2 %) in intestine (P < 0.05). In addition, 0.1 and 0.3 % yeast polysaccharide supplementation improved the number of goblet cells (P < 0.05). The results of this trial indicate that yeast polysaccharides supplementation could affect blood monocytes, improve leukocytes phagocytic activity, and the development of intestine in channel catfish.

The human nociceptor-specific voltage-gated sodium channel 1.7 (hNaV1.7) is critical for sensing various types of somatic pain, but it appears not to play a primary role in acute visceral pain. However, its role in chronic visceral pain remains to be determined. We used assay-guided fractionation to isolate a novel hNaV1.7 inhibitor, Tsp1a, from tarantula venom. Tsp1a is 28-residue peptide that potently inhibits hNaV1.7 (IC50 = 10 nM), with greater than 100-fold selectivity over hNaV1.3–hNaV1.6, 45-fold selectivity over hNaV1.1, and 24-fold selectivity over hNaV1.2. Tsp1a is a gating modifier that inhibits NaV1.7 by inducing a hyperpolarizing shift in the voltage-dependence of channel inactivation and slowing recovery from fast inactivation. NMR studies revealed that Tsp1a adopts a classical knottin fold, and like many knottin peptides, it is exceptionally stable in human serum. Remarkably, intracolonic administration of Tsp1a completely reversed chronic visceral hypersensitivity in a mouse model of irritable bowel syndrome. The ability of Tsp1a to reduce visceral hypersensitivity in a model of irritable bowel syndrome suggests that pharmacological inhibition of hNaV1.7 at peripheral sensory nerve endings might be a viable approach for eliciting analgesia in patients suffering from chronic visceral pain.

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