Technion – Israel Institute of Technology

About: Technion – Israel Institute of Technology is a education organization based out in Haifa, Israel. It is known for research contribution in the topics: Population & Nonlinear system. The organization has 31714 authors who have published 79377 publications receiving 2603976 citations. The organization is also known as: Technion Israel Institute of Technology & Ṭekhniyon, Makhon ṭekhnologi le-Yiśraʼel.

On the Role of Sparse and Redundant Representations in Image Processing

Abstract: Much of the progress made in image processing in the past decades can be attributed to better modeling of image content and a wise deployment of these models in relevant applications. This path of models spans from the simple l2-norm smoothness through robust, thus edge preserving, measures of smoothness (e.g. total variation), and until the very recent models that employ sparse and redundant representations. In this paper, we review the role of this recent model in image processing, its rationale, and models related to it. As it turns out, the field of image processing is one of the main beneficiaries from the recent progress made in the theory and practice of sparse and redundant representations. We discuss ways to employ these tools for various image-processing tasks and present several applications in which state-of-the-art results are obtained.

Regulation of stability and function of the epithelial Na+ channel (ENaC) by ubiquitination.

Abstract: The epithelial Na+ channel (ENaC), composed of three subunits (alpha beta gamma), plays a critical role in salt and fluid homeostasis. Abnormalities in channel opening and numbers have been linked to several genetic disorders, including cystic fibrosis, pseudohypoaldosteronism type I and Liddle syndrome. We have recently identified the ubiquitin-protein ligase Nedd4 as an interacting protein of ENaC. Here we show that ENaC is a short-lived protein (t1/2 approximately 1 h) that is ubiquitinated in vivo on the alpha and gamma (but not beta) subunits. Mutation of a cluster of Lys residues (to Arg) at the N-terminus of gamma ENaC leads to both inhibition of ubiquitination and increased channel activity, an effect augmented by N-terminal Lys to Arg mutations in alpha ENaC, but not in beta ENaC. This elevated channel activity is caused by an increase in the number of channels present at the plasma membrane; it represents increases in both cell-surface retention or recycling of ENaC and incorporation of new channels at the plasma membrane, as determined by Brefeldin A treatment. In addition, we find that the rapid turnover of the total pool of cellular ENaC is attenuated by inhibitors of both the proteasome and the lysosomal/endosomal degradation systems, and propose that whereas the unassembled subunits are degraded by the proteasome, the assembled alpha beta gamma ENaC complex is targeted for lysosomal degradation. Our results suggest that ENaC function is regulated by ubiquitination, and propose a paradigm for ubiquitination-mediated regulation of ion channels.

Mechanism of shape determination in motile cells

Abstract: The shape of motile cells is determined by many dynamic processes spanning several orders of magnitude in space and time, from local polymerization of actin monomers at subsecond timescales to global, cell-scale geometry that may persist for hours. Understanding the mechanism of shape determination in cells has proved to be extremely challenging due to the numerous components involved and the complexity of their interactions. Here we harness the natural phenotypic variability in a large population of motile epithelial keratocytes from fish (Hypsophrys nicaraguensis) to reveal mechanisms of shape determination. We find that the cells inhabit a low-dimensional, highly correlated spectrum of possible functional states. We further show that a model of actin network treadmilling in an inextensible membrane bag can quantitatively recapitulate this spectrum and predict both cell shape and speed. Our model provides a simple biochemical and biophysical basis for the observed morphology and behaviour of motile cells.