Nicotinic Receptor Interloop Proline Anchors β1-β2 and Cys loops in Coupling Agonist Binding to Channel Gating

Nicotinic acetylcholine receptors (AChRs) mediate rapid excitatory synaptic transmission throughout the peripheral and central nervous systems. They transduce binding of nerve-released ACh into opening of an intrinsic channel, yet the structural basis underlying transduction is not fully understood. Previous studies revealed a principal transduction pathway in which αArg 209 of the pre-M1 domain and αGlu 45 of the β1–β2 loop functionally link the two regions, positioning αVal 46 of the β1–β2 loop in a cavity formed by αPro 272 through αSer 269 of the M2–M3 loop. Here we investigate contributions of residues within and proximal to this pathway using single-channel kinetic analysis, site-directed mutagenesis, and thermodynamic mutant cycle analysis. We find that in contributing to channel gating, αVal 46 and αVal 132 of the signature Cys loop couple energetically to αPro 272. Furthermore, these residues are optimized in both their size and hydrophobicity to mediate rapid and efficient channel gating, suggesting naturally occurring substitutions at these positions enable a diverse range of gating rate constants among the Cys-loop receptor superfamily. The overall results indicate that αPro 272 functionally couples to flanking Val residues extending from the β1–β2 and Cys loops within the ACh binding to channel opening transduction pathway

Modular Nucleic Acid Assembled p/MHC Microarrays for Multiplexed Sorting of Antigen-Specific T Cells

The human immune system consists of a large number of T cells capable of recognizing and responding to antigens derived from various sources. The development of peptide-major histocompatibility (p/MHC) tetrameric complexes has enabled the direct detection of these antigen-specific T cells. With the goal of increasing throughput and multiplexing of T cell detection, protein microarrays spotted with defined p/MHC complexes have been reported, but studies have been limited due to the inherent instability and reproducibility of arrays produced via conventional spotted methods. Herein, we report on a platform for the detection of antigen-specific T cells on glass substrates that offers significant advantages over existing surface-bound schemes. In this approach, called “Nucleic Acid Cell Sorting (NACS)”, single-stranded DNA oligomers conjugated site-specifically to p/MHC tetramers are employed to immobilize p/MHC tetramers via hybridization to a complementary-printed substrate. Fully assembled p/MHC arrays are used to detect and enumerate T cells captured from cellular suspensions, including primary human T cells collected from cancer patients. NACS arrays outperform conventional spotted arrays assessed in key criteria such as repeatability and homogeneity. The versatility of employing DNA sequences for cell sorting is exploited to enable the programmed, selective release of target populations of immobilized T cells with restriction endonucleases for downstream analysis. Because of the performance, facile and modular assembly of p/MHC tetramer arrays, NACS holds promise as a versatile platform for multiplexed T cell detection

Citations in supplementary material

The problem of undercounting of citations that are published only in supplementary material is studied for the journals Nature, Science, Cell and the Proceedings of the National Academy of Sciences (USA)

Contribution of deformation to sea-ice mass balance: a case study from an N-ICE2015 storm

The fastest and most efficient process of gaining sea ice volume is through the mechanical redistribution of mass as a consequence of deformation events. During the ice growth season divergent motion produces leads where new ice grows thermodynamically, while convergent motion fractures the ice and either piles the resultant ice blocks into ridges or rafts one floe under the other. Here we present an exceptionally detailed airborne dataset from a 9km2 area of first and second year ice in the Transpolar Drift north of Svalbard that allowed us to estimate the redistribution of mass from an observed deformation event. To achieve this level of detail we analyzed changes in sea ice freeboard acquired from two airborne laser scanner surveys just before and right after a deformation event brought on by a passing low pressure system. A linear regression model based on divergence during this storm can explain 64% of freeboard variability. Over the survey region we estimated that about 1.3% of level sea ice volume was pressed together into deformed ice and the new ice formed in leads in a week after the deformation event would increase the sea ice volume by 0.5%. As the region is impacted by about 15 storms each winter a simple linear extrapolation would result in about 7% volume increase and 20% deformed ice fraction at the end of the seaso

Continuous selections of Lipschitz extensions in metric spaces

This paper deals with the study of parameter dependence of extensions of Lipschitz mappings from the point of view of continuity. We show that if assuming appropriate curvature bounds for the spaces, the multivalued extension operators that assign to every nonexpansive (resp. Lipschitz) mapping all its nonexpansive extensions (resp. Lipschitz extensions with the same Lipschitz constant) are lower semi-continuous and admit continuous selections. Moreover, we prove that Lipschitz mappings can be extended continuously even when imposing the condition that the image of the extension belongs to the closure of the convex hull of the image of the original mapping. When the target space is hyperconvex one can obtain in fact nonexpansivity.Dirección General de Enseñanza SuperiorJunta de AndalucíaRomanian Ministry of Educatio