A minK-HERG complex regulates the cardiac potassium current I(Kr).

MinK is a widely expressed protein of relative molecular mass approximately 15K that forms potassium channels by aggregation with other membrane proteins. MinK governs ion channel activation, regulation by second messengers, and the function and structure of the ion conduction pathway. Association of minK with a channel protein known as KvLQT1 produces a voltage-gated outward K+ current (I[sK]) resembling the slow cardiac repolarization current (I[Ks]). HERG, a human homologue of the ether-a-go-go gene of the fruitfly Drosophila melanogaster, encodes a protein that produces the rapidly activating cardiac delayed rectifier (I[Kr]). These two potassium currents, I(Ks) and I(Kr), provide the principal repolarizing currents in cardiac myocytes for the termination of action potentials. Although heterologously expressed HERG channels are largely indistinguishable from native cardiac I(Kr), a role for minK in this current is suggested by the diminished I(Kr) in an atrial tumour line subjected to minK antisense suppression. Here we show that HERG and minK form a stable complex, and that this heteromultimerization regulates I(Kr) activity. MinK, through the formation of heteromeric channel complexes, is thus central to the control of the heart rate and rhythm

Time-resolved photoluminescence spectra of strong visible light-emitting SiC nanocrystalline films on Si deposited by electron-cyclotron-resonance chemical-vapor deposition

SiC nanocrystalline films on Si substrates deposited using advanced electron-cyclotron-resonance chemical-vapor deposition exhibit intense visible light emission at room temperature under laser excitation. Continuous-wave and time-resolved photoluminescence measurements for these SiC films were carried out at room temperature. The photon energy of the dominant emission peaks is higher than the band gap of cubic SiC. Room-temperature optical absorption measurements show a clear blueshift of the band gap of the samples with a decrease of the average size of the nanoclusters, indicating an expected quantum-confinement effect. However, the emission spectra are basically independent of the size. Temporal evolution of the dominant emissions exhibits double-exponential decay processes. Two distinct decay times of ∼200 ps and ∼1 ns were identified, which are at least two orders of magnitude faster than that of the bound-exciton transitions in bulk 3C-SiC at low temperature. Strong light emissions and short decay times strongly suggest that the radiative recombinations may be from some direct transitions such as self-trapped excitons on the surface of the nanoclusters. © 2000 American Institute of Physics.published_or_final_versio

Antitumor lectin Sclerotium rolfsii (SRL) induces apoptosis in human colon cancer cells by activation of multiple signaling pathways; A microarray analysis

Background: TF antigen specific Sclerotium rolfsii lectin (SRL) inhibits human colon epithelial cancer HT29 cell growth by induction of apoptosis through cell surface binding and has tumor suppressing effect in vivo as reported earlier. Here we report the purification, identification and characterization of SRL binding membrane proteins from HT29 cells. Methods and Findings: Membrane proteins from HT29 cells were isolated by phase separation and purified by affinity chromatography using SRL-Sepharose4B matrix. Affinity purified proteins were subjected to in-gel and in-solution trypsin digestion, analysed by ESI-Q-TOF LC-MS and spectrum mill software. Considering the specificity of SRL towards O-glycans, the presence of O-GalNAc sites in SRL interacting proteins were tested using NetOGlyc software. Western blotting was performed to validate the MS identified proteins. A major protein band around 25kDa following in-gel trypsin digestion was identified as Keratin 1 by MS. In-solution trypsin digestion followed by MS identified 25 SRL interacting proteins namely, keratins, heat shock proteins, tubulins, pyruvate kinase M1/M2, peroxiredoxin-1, ATP synthase subunit alpha, mitochondrial, retinal dehydrogenase 1, actin, annexin-A2, prohibitin, ADP/ATP translocase-2 and alpha enolase. NetOGlyc software analysis revealed 21 proteins positive for O-glycosylation sites including keratins alone containing 27 to 50 O-GalNAc sites. Keratin 1 identified and validated by western blotting as major SRL interacting protein showed 49 O-GalNAc sites. Conclusion: SRL binding membrane proteins from human colon epithelial cancer HT29 cells have been identified and characterized. Identified proteins contain O-GalNAc sites and are known to be involved in cell survival, apoptosis and tumorigenesis. The present study provides insights in studying the mechanism of SRL induced apoptosis and to explore lectin for its clinical implications. Key words: Sclerotium rolfsii lectin; HT29 cell membrane proteins; NetOGlyc version 4.0; Q-TOF-LC/MS; Spectrum Mill. Abbreviations: SRL: Sclerotium rolfsii lectin; LC/MS: Liquid chromatography/Mass spectrometry; ESI: Electro Spray Ionization; Q-TOF: Quadrupole- Time of Flight; PTM: Post Translational Modification; ACN: Acetonitrile; CBB: Coomassie Brilliant Blue; BSA: Bovine Serum Albumin

Software for full-color 3D reconstruction of the biological tissues internal structure

A software for processing sets of full-color images of biological tissue histological sections is developed. We used histological sections obtained by the method of high-precision layer-by-layer grinding of frozen biological tissues. The software allows restoring the image of the tissue for an arbitrary cross-section of the tissue sample. Thus, our method is designed to create a full-color 3D reconstruction of the biological tissue structure. The resolution of 3D reconstruction is determined by the quality of the initial histological sections. The newly developed technology available to us provides a resolution of up to 5 - 10 {\mu}m in three dimensions.Comment: 11 pages, 8 figure

Big bang simulation in superfluid 3He-B -- Vortex nucleation in neutron-irradiated superflow

We report the observation of vortex formation upon the absorption of a thermal neutron in a rotating container of superfluid $^3$He-B. The nuclear reaction n + $^3$He = p + $^3$H + 0.76MeV heats a cigar shaped region of the superfluid into the normal phase. The subsequent cooling of this region back through the superfluid transition results in the nucleation of quantized vortices. Depending on the superflow velocity, sufficiently large vortex rings grow under the influence of the Magnus force and escape into the container volume where they are detected individually with nuclear magnetic resonance. The larger the superflow velocity the smaller the rings which can expand. Thus it is possible to obtain information about the morphology of the initial defect network. We suggest that the nucleation of vortices during the rapid cool-down into the superfluid phase is similar to the formation of defects during cosmological phase transitions in the early universe.Comment: 4 pages, LaTeX file, 4 figures are available at ftp://boojum.hut.fi/pub/publications/lowtemp/LTL-95009.p

Regulatory control and the costs and benefits of biochemical noise

Experiments in recent years have vividly demonstrated that gene expression can be highly stochastic. How protein concentration fluctuations affect the growth rate of a population of cells, is, however, a wide open question. We present a mathematical model that makes it possible to quantify the effect of protein concentration fluctuations on the growth rate of a population of genetically identical cells. The model predicts that the population's growth rate depends on how the growth rate of a single cell varies with protein concentration, the variance of the protein concentration fluctuations, and the correlation time of these fluctuations. The model also predicts that when the average concentration of a protein is close to the value that maximizes the growth rate, fluctuations in its concentration always reduce the growth rate. However, when the average protein concentration deviates sufficiently from the optimal level, fluctuations can enhance the growth rate of the population, even when the growth rate of a cell depends linearly on the protein concentration. The model also shows that the ensemble or population average of a quantity, such as the average protein expression level or its variance, is in general not equal to its time average as obtained from tracing a single cell and its descendants. We apply our model to perform a cost-benefit analysis of gene regulatory control. Our analysis predicts that the optimal expression level of a gene regulatory protein is determined by the trade-off between the cost of synthesizing the regulatory protein and the benefit of minimizing the fluctuations in the expression of its target gene. We discuss possible experiments that could test our predictions.Comment: Revised manuscript;35 pages, 4 figures, REVTeX4; to appear in PLoS Computational Biolog

Wnt5a induces ROR1 to associate with 14-3-3ζ for enhanced chemotaxis and proliferation of chronic lymphocytic leukemia cells.

Wnt5a can activate Rho GTPases in chronic lymphocytic leukemia (CLL) cells by inducing the recruitment of ARHGEF2 to ROR1. Mass spectrometry on immune precipitates of Wnt5a-activated ROR1 identified 14-3-3ζ, which was confirmed by co-immunoprecipitation. The capacity of Wnt5a to induce ROR1 to complex with 14-3-3ζ could be blocked in CLL cells by treatment with cirmtuzumab, a humanized mAb targeting ROR1. Silencing 14-3-3ζ via small interfering RNA impaired the capacity of Wnt5a to: (1) induce recruitment of ARHGEF2 to ROR1, (2) enhance in vitro exchange activity of ARHGEF2 and (3) induce activation of RhoA and Rac1 in CLL cells. Furthermore, CRISPR/Cas9 deletion of 14-3-3ζ in ROR1-negative CLL cell-line MEC1, and in MEC1 cells transfected to express ROR1 (MEC1-ROR1), demonstrated that 14-3-3ζ was necessary for the growth/engraftment advantage of MEC1-ROR1 over MEC1 cells. We identified a binding motif (RSPS857SAS) in ROR1 for 14-3-3ζ. Site-directed mutagenesis of ROR1 demonstrated that serine-857 was required for the recruitment of 14-3-3ζ and ARHGEF2 to ROR1, and activation of RhoA and Rac1. Collectively, this study reveals that 14-3-3ζ plays a critical role in Wnt5a/ROR1 signaling, leading to enhanced CLL migration and proliferation