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Kai Johnsson

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Related publications (122)

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The metabolite BH4 controls T cell proliferation in autoimmunity and cancer

Kai Johnsson, Jairo Alexander Lozano Moreno, Yann Mathieu Pierson

Genetic regulators and environmental stimuli modulate T cell activation in autoimmunity and cancer. The enzyme co-factor tetrahydrobiopterin (BH4) is involved in the production of monoamine neurotransmitters, the generation of nitric oxide, and pain(1,2). ...

NATURE PUBLISHING GROUP2018

6,11-Dioxobenzo[f]pyrido[1,2-a]indoles Kill Mycobacterium tuberculosis by Targeting Iron-Sulfur Protein Rv0338c (IspQ), A Putative Redox Sensor

Edina Rita Székely, Stewart Cole, Kai Johnsson, Andrej Benjak, Jérémie Piton, Monica Rengifo Gonzalez

Screening of a diversity-oriented compound library led to the identification of two 6,11-dioxobenzo[f]pyrido[1,2-a]indoles (DBPI) that displayed low micromolar bactericidal activity against the Erdman strain of Mycobacterium tuberculosis in vitro. The acti ...

AMER CHEMICAL SOC2020

Substrates for Improved Live-Cell Fluorescence Labeling of SNAP-tag

Kai Johnsson, Luc Reymond, Grazvydas Lukinavicius

The SNAP-tag labeling technology provides a simple, robust, and versatile approach to the imaging of fusion proteins for a wide range of experimental applications. Owing to the specific and covalent nature of the labeling reaction, SNAP-tag is well suited ...

Bentham Science Publ Ltd2013

AspSnFR: A genetically encoded biosensor for real-time monitoring of aspartate in live cells

Kai Johnsson

Aspartate is crucial for nucleotide synthesis, ammonia detoxification, and maintaining redox balance via the malate-aspartate-shuttle (MAS). To disentangle these multiple roles of aspartate metabolism, tools are required that measure aspartate concentratio ...

CELL PRESS2024

FRET imaging reveals that functional neurokinin-1 receptors are monomeric and reside in membrane microdomains of live cells

Horst Arthur Vogel, Kai Johnsson, Rudolf Hovius, Jean-Manuel Segura, Nathalie George

The lateral organization of a prototypical G protein-coupled receptor, the neurokinin-1 receptor (NK1R), was investigated in living cells by fluorescence resonance energy transfer (FRET) microscopy, taking advantage of the recently developed acyl carrier p ...

National Academy of Sciences2006

Measuring In Vivo Protein Half-Life

Didier Trono, Kai Johnsson, Christian Heinis, Sandra Eloise Kjeldsen, Sonia Verp, Isabelle Barde, Karolina Bojkowska

Protein turnover critically influences many biological functions, yet methods have been lacking to assess this parameter in vivo. Here, we demonstrate how chemical labeling of SNAP-tag fusion proteins can be exploited to measure the half-life of resident i ...

Elsevier2011

Exchangeable HaloTag Ligands for Super-Resolution Fluorescence Microscopy

Kai Johnsson, Michelle Susanne Frei

The specific and covalent labeling of the protein HaloTag with fluorescent probes in living cells makes it a powerful tool for bioimaging. However, the irreversible attachment of the probe to HaloTag precludes imaging applications that require transient bi ...

AMER CHEMICAL SOC2023

Chemical Biology Approaches to Membrane Homeostasis and Function

Kai Johnsson, Christian Heinis, Gerardo Turcatti, Luc Reymond

The study of membranes is at a turning point. New theories about membrane structure and function have recently been proposed, however, new technologies, combining chemical, physical, and biochemical approaches are necessary to test these hypotheses. In par ...

2011

Systematic Tuning of Rhodamine Spirocyclization for Super-resolution Microscopy

Kai Johnsson, Lu Wang

Rhodamines are the most important class of fluorophores for applications in live-cell fluorescence microscopy. This is mainly because rhodamines exist in a dynamic equilibrium between a fluorescent zwitterion and a nonfluorescent but cell-permeable spirocy ...

AMER CHEMICAL SOC2021

Small-Molecule Fluorescent Probes for Live-Cell Super-Resolution Microscopy

Kai Johnsson, Lu Wang, Michelle Susanne Frei, Aleksandar Salim

Super-resolution fluorescence microscopy is a powerful tool to visualize biomolecules and cellular structures at the nanometer scale. Employing these techniques in living cells has opened up the possibility to study dynamic processes with unprecedented spa ...

AMER CHEMICAL SOC2019

Fluorogenic Rhodamine-Based Chemigenetic Biosensor for Monitoring Cellular NADPH Dynamics

Kai Johnsson

Ratiometric biosensors employing Forster Resonance Energy Transfer (FRET) enable the real-time tracking of metabolite dynamics. Here, we introduce an approach for generating a FRET-based biosensor in which changes in apparent FRET efficiency rely on the an ...

AMER CHEMICAL SOC2024

SLC25A51 is a mammalian mitochondrial NAD(+) transporter

Kai Johnsson

Mitochondria require nicotinamide adenine dinucleotide (NAD(+)) to carry out the fundamental processes that fuel respiration and mediate cellular energy transduction. Mitochondrial NAD(+) transporters have been identified in yeast and plants(1,2), but thei ...

NATURE RESEARCH2020

Exploiting Ligand-Protein Conjugates to Monitor Ligand-Receptor Interactions

Kai Johnsson, Hirohito Haruki, Monica Rengifo Gonzalez

We introduce three assays for analyzing ligand-receptor interactions based on the specific conjugation of ligands to SNAP-tag fusion proteins. Conjugation of ligands to different SNAP-tag fusions permits the validation of suspected interactions in cell ext ...

Public Library of Science2012

A general method for the development of multicolor biosensors with large dynamic ranges

Kai Johnsson

Fluorescent biosensors enable the study of cell physiology with spatiotemporal resolution; yet, most biosensors suffer from relatively low dynamic ranges. Here, we introduce a family of designed Forster resonance energy transfer (FRET) pairs with near-quan ...

NATURE PORTFOLIO2023

Searching for the Protein Targets of Bioactive Molecules

Kai Johnsson, Christopher Chidley, Cindy Fellay, Miriam Grønlund Pedersen, Hirohito Haruki, Simone Moser

The identification of all protein targets of a given drug or bioactive molecule within the human body is a prerequisite for an understanding of its beneficial and deleterious activities. Current approaches to reveal protein targets often fail to reveal phy ...

Schweizerische Chemische Gesellschaft2011

Unintended specificity of an engineered ligand-binding protein facilitated by unpredicted plasticity of the protein fold

Kai Johnsson, Alberto Schena

Attempts to create novel ligand-binding proteins often focus on formation of a binding pocket with shape complementarity against the desired ligand (particularly for compounds that lack distinct polar moieties). Although designed proteins often exhibit bin ...

OXFORD UNIV PRESS2018

Imaging and manipulating proteins in live cells through covalent labeling

Kai Johnsson, Lin Xue, Julien Hiblot, Iuliia Karpenko

The past 20 years have witnessed the advent of numerous technologies to specifically and covalently label proteins in cellulo and in vivo with synthetic probes. These technologies range from self-labeling proteins tags to non-natural amino acids, and the q ...

Nature Publishing Group2015

A ligand-based system for receptor-specific delivery of proteins

Kai Johnsson, Luc Reymond

Gene delivery using vector or viral-based methods is often limited by technical and safety barriers. A promising alternative that circumvents these shortcomings is the direct delivery of proteins into cells. Here we introduce a non-viral, ligand-mediated p ...

Springer Nature2019

Low temperature and mTOR inhibition favor stem cell maintenance in human keratinocyte cultures

Kai Johnsson, Yann Barrandon, Thomas Michael Braschler, Ariane Rochat, Jean-Baptiste Bureau, Fahd Azzabi Zouraq, Johannes Alexander Mosig

Adult autologous human epidermal stem cells can be extensively expanded ex vivo for cell and gene therapy. Identifying the mechanisms involved in stem cell maintenance and defining culture conditions to maintain stemness is critical, because an inadequate ...

WILEY2023

Protein function microarrays based on self-immobilizing and self-labeling fusion proteins

Harm-Anton Klok, Kai Johnsson, Stefano Tugulu, India Christina Sielaff, Anke Arnold

Protein microarrays are an attractive approach for the high-throughput analysis of protein function, but their impact on proteomics has been limited by the technical difficulties associated with their generation. Here we demonstrate that fusion proteins of ...

2006