Reflectin as a Material for Neural Stem Cell Growth.

Cephalopods possess remarkable camouflage capabilities, which are enabled by their complex skin structure and sophisticated nervous system. Such unique characteristics have in turn inspired the design of novel functional materials and devices. Within this context, recent studies have focused on investigating the self-assembly, optical, and electrical properties of reflectin, a protein that plays a key role in cephalopod structural coloration. Herein, we report the discovery that reflectin constitutes an effective material for the growth of human neural stem/progenitor cells. Our findings may hold relevance both for understanding cephalopod embryogenesis and for developing improved protein-based bioelectronic devices.

Evidence for functional diversity between the voltage-gated proton channel Hv1 and its closest related protein HVRP1.

The Hv1 channel and voltage-sensitive phosphatases share with voltage-gated sodium, potassium, and calcium channels the ability to detect changes in membrane potential through voltage-sensing domains (VSDs). However, they lack the pore domain typical of these other channels. NaV, KV, and CaV proteins can be found in neurons and muscles, where they play important roles in electrical excitability. In contrast, VSD-containing proteins lacking a pore domain are found in non-excitable cells and are not involved in neuronal signaling. Here, we report the identification of HVRP1, a protein related to the Hv1 channel (from which the name Hv1 Related Protein 1 is derived), which we find to be expressed primarily in the central nervous system, and particularly in the cerebellum. Within the cerebellar tissue, HVRP1 is specifically expressed in granule neurons, as determined by in situ hybridization and immunohistochemistry. Analysis of subcellular distribution via electron microscopy and immunogold labeling reveals that the protein localizes on the post-synaptic side of contacts between glutamatergic mossy fibers and the granule cells. We also find that, despite the similarities in amino acid sequence and structural organization between Hv1 and HVRP1, the two proteins have distinct functional properties. The high conservation of HVRP1 in vertebrates and its cellular and subcellular localizations suggest an important function in the nervous system.

Molecular determinants of Hv1 proton channel inhibition by guanidine derivatives.

The voltage-gated proton channel Hv1 plays important roles in proton extrusion, pH homeostasis, and production of reactive oxygen species in a variety of cell types. Excessive Hv1 activity increases proliferation and invasiveness in cancer cells and worsens brain damage in ischemic stroke. The channel is composed of two subunits, each containing a proton-permeable voltage-sensing domain (VSD) and lacking the pore domain typical of other voltage-gated ion channels. We have previously shown that the compound 2-guanidinobenzimidazole (2GBI) inhibits Hv1 proton conduction by binding to the VSD from its intracellular side. Here, we examine the binding affinities of a series of 2GBI derivatives on human Hv1 channels mutated at positions located in the core of the VSD and apply mutant cycle analysis to determine how the inhibitor interacts with the channel. We identify four Hv1 residues involved in the binding: aspartate 112, phenylalanine 150, serine 181, and arginine 211. 2GBI appears to be oriented in the binding site with its benzo ring pointing to F150, its imidazole ring inserted between residue D112 and residues S181 and R211, and the guanidine group positioned in the proximity of R211. We also identify a modified version of 2GBI that is able to reach the binding site on Hv1 from the extracellular side of the membrane. Understanding how compounds like 2GBI interact with the Hv1 channel is an important step to the development of pharmacological treatments for diseases caused by Hv1 hyperactivity.

Voltage-sensing domain of voltage-gated proton channel Hv1 shares mechanism of block with pore domains.

Voltage-gated sodium, potassium, and calcium channels are made of a pore domain (PD) controlled by four voltage-sensing domains (VSDs). The PD contains the ion permeation pathway and the activation gate located on the intracellular side of the membrane. A large number of small molecules are known to inhibit the PD by acting as open channel blockers. The voltage-gated proton channel Hv1 is made of two VSDs and lacks the PD. The location of the activation gate in the VSD is unknown and open channel blockers for VSDs have not yet been identified. Here, we describe a class of small molecules which act as open channel blockers on the Hv1 VSD and find that a highly conserved phenylalanine in the charge transfer center of the VSD plays a key role in blocker binding. We then use one of the blockers to show that Hv1 contains two intracellular and allosterically coupled gates.

Comparative efficacy of biologics in psoriasis: a review.

BACKGROUND: Psoriasis is a chronic, immune-mediated skin disease that also has systemic manifestations. Safe and effective long-term treatments are needed. Biologic treatments that inhibit the immunopathogenesis of psoriasis have helped meet this need. PURPOSE: The purpose of this study was to compare the efficacy of biologic therapies used for psoriasis. METHODS: A literature search was performed using PubMed and the keywords '(PASI-75 OR efficacy) AND psoriasis AND (adalimumab OR alefacept OR etanercept OR infliximab OR ustekinumab).' Randomized, double-blind, and placebo-controlled studies on US FDA-approved biologics were selected. Studies assessing the proportion of subjects achieving 75% improvement in Psoriasis Area and Severity Index (PASI-75) within a 12-week period were included. Studies on pediatric populations and psoriatic arthritis were excluded. The weighted average of PASI-75 for each reported regimen was calculated to determine the efficacy of biologic agents used for moderate-to-severe psoriasis. Tolerance and secondary efficacy measures were also examined for the selected studies. RESULTS: FDA-approved regimens of adalimumab, infliximab, ustekinumab, and alefacept were effective in treating moderate-to-severe psoriasis. Weighted average PASI-75 scores for infliximab, ustekinumab, adalimumab, etanercept, and alefacept were 78.6%, 72.1%, 70.5%, 48.1%, and 21%, respectively. LIMITATIONS: The comparative efficacy of biologic agents data was limited to 12 weeks, thus generalizing the results to longer treatment periods may not be accurate. CONCLUSIONS: Various biologic agents for psoriasis were effective at 12 weeks in placebo-controlled trials. Available data cannot fully account for situations in clinical practice, in which combination and longer duration of therapy may be required. When choosing the most effective or best agent, multiple factors should be considered including patient preference, cost, tolerance, adverse effects, dosing schedule, and mode of administration.