Ferroptosis has recently attracted much interest because of its relevance to human diseases such as cancer and ischemia‐reperfusion injury. We have reported that prolonged severe cold stress induces ...lipid peroxidation‐dependent ferroptosis, but the upstream mechanism remains unknown. Here, using genome‐wide CRISPR screening, we found that a mitochondrial Ca2+ uptake regulator, mitochondrial calcium uptake 1 (MICU1), is required for generating lipid peroxide and subsequent ferroptosis under cold stress. Furthermore, the gatekeeping activity of MICU1 through mitochondrial calcium uniporter (MCU) is suggested to be indispensable for cold stress‐induced ferroptosis. MICU1 is required for mitochondrial Ca2+ increase, hyperpolarization of the mitochondrial membrane potential (MMP), and subsequent lipid peroxidation under cold stress. Collectively, these findings suggest that the MICU1‐dependent mitochondrial Ca2+ homeostasis‐MMP hyperpolarization axis is involved in cold stress‐induced lipid peroxidation and ferroptosis.
SYNOPSIS
This study identifies MICU1 as a key regulator for lipid peroxidation and subsequent ferroptosis under cold stress, suggesting that MICU1 can be a potential target for preventing cell death in organ preservation.
Genome‐wide CRISPR screening reveals that MICU1 is required for cold stress‐induced ferroptosis.
MICU1 deficiency attenuates lipid peroxidation via suppressing hyperpolarization of the mitochondrial membrane potential and mitochondrial Ca2 + uptake induced by cold stress.
Intracellular Ca2 + increase, partly through TRPM8, plays important roles in cold stress‐induced ferroptosis.
This study identifies MICU1 as a key regulator for lipid peroxidation and subsequent ferroptosis under cold stress, suggesting that MICU1 can be a potential target for preventing cell death in organ preservation.
Recent studies have shown that adipose tissue is an immunological organ. While inflammation in energy-storing white adipose tissues has been the focus of intense research, the regulatory mechanisms ...of inflammation in heat-producing brown adipose tissues remain largely unknown. We previously identified apoptosis signal-regulating kinase 1 (ASK1) as a critical regulator of brown adipocyte maturation; the PKA-ASK1-p38 axis facilitates uncoupling protein 1 (UCP1) induction cell-autonomously. Here, we show that ASK1 suppresses an innate immune pathway and contributes to maintenance of brown adipocytes. We report a novel chemical pull-down method for endogenous kinases using analog sensitive kinase allele (ASKA) technology and identify an ASK1 interactor in brown adipocytes, receptor-interacting serine/threonine-protein kinase 2 (RIPK2). ASK1 disrupts the RIPK2 signaling complex and inhibits the NOD-RIPK2 pathway to downregulate the production of inflammatory cytokines. As a potential biological significance, an in vitro model for intercellular regulation suggests that ASK1 facilitates the expression of UCP1 through the suppression of inflammatory cytokine production. In parallel to our previous report on the PKA-ASK1-p38 axis, our work raises the possibility of an auxiliary role of ASK1 in brown adipocyte maintenance through neutralizing the thermogenesis-suppressive effect of the NOD-RIPK2 pathway.
A wide variety of cell death mechanisms, such as ferroptosis, have been proposed in mammalian cells, and the classification of cell death attracts global attention because each type of cell death has ...the potential to play causative roles in specific diseases. However, the precise molecular mechanisms leading to cell death are poorly understood, particularly in ferroptosis. Here, we show that continuous severe cold stress induces ferroptosis and the ASK1‐p38 MAPK pathway in multiple cell lines. The activation of the ASK1‐p38 pathway is mediated by critical determinants of ferroptosis: MEK activity, iron ions, and lipid peroxide. The chemical compound erastin, a potent ferroptosis inducer, also activates the ASK1‐p38 axis downstream of lipid peroxide accumulation and leads to ASK1‐dependent cell death in a cell type‐specific manner. These lines of evidence provide mechanistic insight into ferroptosis, a type of regulated necrosis.
Synopsis
The molecular mechanisms leading to ferroptotic cell death are poorly understood. This study shows that sustained cold stress induces ferroptosis and lipid peroxide accumulation, which activates the ASK1‐p38 signaling axis.
Cold stress induces ferroptosis in multiple cell lines.
The ASK1‐p38 axis is activated by cold stress downstream of lipid peroxide.
The ASK1‐p38 axis is also activated by other pro‐ferroptotic conditions and is involved in cell death regulation in a cell type‐specific manner.
The molecular mechanisms leading to ferroptotic cell death are poorly understood. This study shows that sustained cold stress induces ferroptosis and lipid peroxide accumulation, which activates the ASK1‐p38 signaling axis.
•Firstly studied was effect of MHz ultrasound on crystallization of glycine.•The irradiation of 1.6MHz ultrasound enhanced the growth of glycine crystal.•The crystal size distribution was narrowed by ...the irradiation.•Incorporation of microcrystal plays an important role in the growth enhancement.•The model developed for the growth successfully predicted the observed values.
Antisolvent crystallization of glycine was performed under ultrasonic irradiation of 1.6MHz. The irradiation enhanced both the growth of α-glycine crystal and the uniformity in the crystal size. The degree of both enhancement effects increased with increasing ultrasonic power. While under the irradiation of 20kHz ultrasound, no growth enhancement was observed, but the crystal size reduced as was reported in the literature. To elucidate the mechanism of growth enhancement, another experiment was designed and conducted to avoid the effect of nucleation from the sonocrystallization. The result suggests that the ultrasound enhances the incorporation of microcrystals to larger crystals. Probably, the collision between solid particles is intensified by the disturbance characterized by the high frequency ultrasound. The crystal growth was modeled with an apparent reaction of microcrystal and larger crystal. The result of the growth experiment was successfully predicted with a rate equation for pseudo first order reaction with a single parameter of rate constant. The rate constant linearly increased with the ultrasonic power. The analysis enables quantitative evaluation of the ultrasonic effect on the crystal growth.
Genetically encoded fluorescent biosensors are powerful tools for monitoring biochemical activities in live cells, but their multiplexing capacity is limited by the available spectral space. We ...overcome this problem by developing a set of barcoding proteins that can generate over 100 barcodes and are spectrally separable from commonly used biosensors. Mixtures of barcoded cells expressing different biosensors are simultaneously imaged and analyzed by deep learning models to achieve massively multiplexed tracking of signaling events. Importantly, different biosensors in cell mixtures show highly coordinated activities, thus facilitating the delineation of their temporal relationship. Simultaneous tracking of multiple biosensors in the receptor tyrosine kinase signaling network reveals distinct mechanisms of effector adaptation, cell autonomous and non-autonomous effects of KRAS mutations, as well as complex interactions in the network. Biosensor barcoding presents a scalable method to expand multiplexing capabilities for deciphering the complexity of signaling networks and their interactions between cells.
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•Large numbers of fluorescent biosensors can be concurrently tracked in barcoded cells•Biosensor activities are synchronized in mixed populations of barcoded cells•Deep learning models facilitate image analysis for biosensor barcoding•Simultaneous biosensor tracking reveals signaling network structures and interactions
Genetically encoded barcodes that uniquely identify cells expressing a particular fluorescent biosensor enable the simultaneous use of a broader set of biosensors in mixed cell populations and dynamic imaging of many cellular responses in a single experiment to reduce inter-experimental variability when interrogating complex biological interactions, such as the downstream consequences of receptor tyrosine kinase activation, with the help of image-based deep learning models for automated barcode unmixing.
Ferroptosis has recently attracted much interest because of its relevance to human diseases such as cancer and ischemia-reperfusion injury. We have reported that prolonged severe cold stress induces ...lipid peroxidation-dependent ferroptosis, but the upstream mechanism remains unknown. Here, using genome-wide CRISPR screening, we found that a mitochondrial Ca
uptake regulator, mitochondrial calcium uptake 1 (MICU1), is required for generating lipid peroxide and subsequent ferroptosis under cold stress. Furthermore, the gatekeeping activity of MICU1 through mitochondrial calcium uniporter (MCU) is suggested to be indispensable for cold stress-induced ferroptosis. MICU1 is required for mitochondrial Ca
increase, hyperpolarization of the mitochondrial membrane potential (MMP), and subsequent lipid peroxidation under cold stress. Collectively, these findings suggest that the MICU1-dependent mitochondrial Ca
homeostasis-MMP hyperpolarization axis is involved in cold stress-induced lipid peroxidation and ferroptosis.
Antisolvent crystallization of glycine was conducted under ultrasonic irradiation of 1.6 MHz and 20 kHz to study the effect of ultrasound on the behavior of crystallization of α-glycine. Irradiation ...of 1.6 MHz ultrasound resulted in a faster transition from β to α form, and also the crystal size of α-glycine increased with increasing ultrasonic power. While under irradiation of 20 kHz, such an enhancement of crystal growth was unobserved, and the crystal size becomes smaller. The mechanism of the crystal growth enhancement was discussed in terms of a threshold of ultrasonic power on both crystal growth and KI oxidation.
Our previous study demonstrated growth enhancement of glycine particles in the crystallization under the irradiation of 1.6 MHz ultrasound. The result indicated that ultrasound enhanced mass-transfer ...around the solid particle in the suspension. To specify the effect of ultrasound contributing the enhancement, we took a simpler approach of observing dissolution of a sparingly soluble compound, benzoic acid, in water under the ultrasonic irradiation. Particles of benzoic acid having a limited size range were mixed into water under a mechanical stirring and sonication. At higher ultrasonic powers, rate coefficients for the dissolution strongly depend on ultrasonic power, which suggests that the ultrasound plays the major role in the enhancement. Even at this condition, the enhancement was lost by the use of degassed water as a solvent. This fact clearly shows that cavitation plays a significant role in the mass-transfer enhancement.
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