Biology subjects

Ballanyi, K.

Publications and source records attributed to Ballanyi, K..

5 recordsLinked to original sources

bioRxiv2024

The ER Thioredoxin-Related Transmembrane Protein TMX2 Controls Redox-Mediated Tethering of ER-Mitochondria Contacts (ERMCS)

Thioredoxin-related transmembrane proteins (TMX) of the endoplasmic reticulum (ER) have emerged as key regulators of ER membrane properties. Within the ER lumen, TMX proteins and other ER redox enzymes determine oxidative conditions, which control the formation of ER-mitochondria membrane contacts (ERMCS) and determine their function. ERMCS exhibit cytoplasmic redox nanodomains, derived from ER and mitochondrial reactive oxygen species (ROS), whose mechanistic regulation is uncharacterized. Our research has identified the ER protein TMX2, which uses its unique cytosolic thioredoxin domain to prevent cytosolic sulfenylation of mitochondrial outer membrane proteins such as TOM70 through a functional interaction with peroxiredoxin-1 (PRDX1). By doing so, TMX2 interferes with the TOM70 ERMCS tethering function and reduces mitochondrial Ca2+ flux and metabolism. Recently, TMX2 mutations have been identified to cause a neurodevelopmental disorder with microcephaly, cortical malformations, and spasticity (NEDMCMS). Using TMX2-mutated NEDMCMS patient cells, we demonstrate that compromising TMX2 through mutation reproduces mitochondrial defects. In a fly in vivo model, TMX2 knockdown manifests predominantly in glial cells. Our results therefore provide important mechanistic insight into NEDMCMS and mechanistically link TMX2-mediated control of ERMCS to brain development and function. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=150 SRC="FIGDIR/small/589228v2_ufig1.gif" ALT="Figure 1"> View larger version (71K): org.highwire.dtl.DTLVardef@809587org.highwire.dtl.DTLVardef@1d8ef0corg.highwire.dtl.DTLVardef@135fdc6org.highwire.dtl.DTLVardef@1a7f7b6_HPS_FORMAT_FIGEXP M_FIG C_FIG The transmembrane thioredoxin-related TMX2 prevents TOM70 sulfenylation at ERMCS, thus maintaining normal mitochondria metabolism in wild-type cells. TMX2 knockout leads to TOM70 sulfenylation and tight ERMCS formation. This then increases ROS production, unbalances mitochondrial lipids, and relatively shifts OXPHOS electron supply to complex II.

cell biology↗

bioRxiv2021

A sensitive and specific genetically encodable biosensor for potassium ions

Potassium ions (K+) play a critical role as an essential electrolyte in all biological systems. Here we report the crystal structure-guided optimization and directed evolution of an improved genetically encoded fluorescent K+ biosensor, GINKO2. GINKO2 is highly sensitive and specific for K+ and enables in vivo detection of K+ dynamics in multiple species.

bioengineering↗

bioRxiv2020

ER stress in the dorsal root ganglia regulates BK channel physiology and contributes to pain hypersensitivity in a mouse model of multiple sclerosis

Neuropathic pain is a common symptom of multiple sclerosis (MS) and current treatment options are ineffective. In this study, we investigated whether endoplasmic reticulum (ER) stress in dorsal root ganglia (DRG) contributes to pain hypersensitivity in the experimental autoimmune encephalomyelitis (EAE) mouse model of MS. Inflammatory cells and increased levels of ER stress markers are evident in post-mortem DRGs from MS patients. Similarly, we observed ER stress in the DRG of mice with EAE and relieving ER stress with a chemical chaperone, 4-phenylbutyric acid (4-PBA), reduced pain hypersensitivity. In vitro, 4-PBA and the selective PERK inhibitor, AMG44, normalize cytosolic Ca2+ transients in putative DRG nociceptors. We went to assess disease-mediated changes in the functional properties of Ca2+-sensitive BK-type K+ channels in DRG neurons. We found that the conductance-voltage (GV) relationship of BK channels was shifted to a more positive voltage, together with a more depolarized resting membrane potential in EAE cells. Our results suggest that ER stress in sensory neurons of MS patients and mice with EAE is a source of pain and that ER stress modulators can effectively counteract this phenotype.

neuroscience↗

bioRxiv2018

Genetically encoded ratiometric indicators for potassium ion

Potassium ion (K+) homeostasis and dynamics play critical roles in regulating various biological activities, and the ability to monitor K+ spatial-temporal dynamics is critical to understanding these biological functions. Here we report the design and characterization of a Forster resonance energy transfer (FRET)-based genetically encoded K+ indicator, KIRIN1, constructed by inserting a bacterial cytosolic K+ binding protein (Kbp) between a fluorescent protein (FP) FRET pair, mCerulean3 and cp173Venus. Binding of K+ induces a conformational change in Kbp, resulting in an increase in FRET efficiency. KIRIN1 was able to detect K+ at physiologically relevant concentrations in vitro and is highly selective toward K+ over Na+. We further demonstrated that KIRIN1 allowed real-time imaging of pharmacologically induced depletion of cytosolic K+ in live cells, and KIRIN1 also enabled optical tracing of K+ efflux and reuptake in neurons upon glutamate stimulation in cultured primary neurons. These results demonstrate that KIRIN1 is a valuable tool to detect K+ in vitro and in live cells.

bioengineering↗

bioRxiv2017

A genetically encoded Ca2+ indicator based on circularly permutated sea anemone red fluorescent protein

Genetically-encoded calcium ion (Ca2+) indicators (GECIs) are indispensable tools for measuring Ca2+ dynamics and neuronal activities in vitro and in vivo. Red fluorescent protein (RFP)-based GECIs enable multicolor visualization with blue or cyan-excitable fluorophores and combined use with blue or cyan-excitable optogenetic actuators. Here we report the development, structure, and validation of a new red fluorescent Ca2+ indicator, K-GECO1, based on a circularly permutated RFP derived from the sea anemone Entacmaea quadricolor. We characterized the performance of K-GECO1 in cultured HeLa cells, dissociated neurons, stem cell derived cardiomyocytes, organotypic brain slices, zebrafish spinal cord in vivo, and mouse brain in vivo.

biophysics↗