Explore the vast range of titles available.

The endocardium plays a pivotal role in governing myocardial development, and understanding the intrinsic regulatory insights will help apprehend pathological cardiomyopathy. Glycerol-3-phosphate acyltransferase 4 (GPAT4) is an endoplasmic reticulum (ER) membrane anchored protein. While the role of GPAT4 in glycerophospholipid biosynthesis is well established, its function in the ER is less explored. Here, we generate Gpat4 global and tissue-specific knockout mice and identify the essential role of GPAT4 in endocardial development. Deficiency of GPAT4 provokes endocardial ER stress response and enhances ER-mitochondrial (ER-mito) communications, leading to mitochondrial DNA (mtDNA) escape. As a result, the cGAS-STING pathway is triggered to stimulate type-I-interferon response, which affects heart development. Finally, abolishment of the cGAS-STING-type-I-interferon pathway rescues the heart defects of Gpat4 deletion mice. These findings uncover the pivotal role of GPAT4 in the maintenance of ER homeostasis during endocardial and heart development. Meanwhile, this study highlights the importance of the cGAS-STING pathway in cardiac organogenesis. Here the authors identify a role of GPAT4 in endocardial and myocardial development through maintaining ER homeostasis. GPAT4 deficiency triggers ER stress, ER-mitochondrial dysfunction, and activation of the cGAS-STING-type I IFN response, leading to severe heart malformation.

Synthetic aperture radar tomography (TomoSAR) has gained significant attention for three-dimensional (3D) imaging in urban environments. A notable limitation of traditional TomoSAR approaches is their primary focus on persistent scatterers (PSs), disregarding targets with temporal decorrelated characteristics. Temporal variations in coherence, especially in urban areas due to the dense population of buildings and artificial structures, can lead to a reduction in detectable PSs and suboptimal 3D reconstruction performance. The concept of partially coherent scatterers (PCSs) has been proven effective by capturing the partial temporal coherence of targets across the entire time baseline. In this study, an novel approach based on an iterative sub-network generation method is introduced to leverage PCSs for enhanced 3D reconstruction in dynamic environments. We propose a coherence constraint iterative variance analysis approach to determine the optimal temporal baseline range that accurately reflects the interferometric coherence of PCSs. Utilizing the selected PCSs, a 3D imaging technique that incorporates the iterative generation of sub-networks into the SAR tomography process is developed. By employing the PS reference network as a foundation, we accurately invert PCSs through the iterative generation of local star-shaped networks, ensuring a comprehensive coverage of PCSs in study areas. The effectiveness of this method for the height estimation of PCSs is validated using the TerraSAR-X dataset. Compared with traditional PS-based TomoSAR, the proposed approach demonstrates that PCS-based elevation results complement those from PSs, significantly improving 3D reconstruction in evolving urban settings.

The current optogenetic toolkit lacks a robust single-component Ca 2+ -selective ion channel tailored for remote control of Ca 2+ signaling in mammals. Existing tools are either derived from engineered channelrhodopsin variants without strict Ca 2+ selectivity or based on the stromal interaction molecule 1 (STIM1) that might crosstalk with other targets. Here, we describe the design of a light-operated Ca 2+ channel (designated LOCa) by inserting a plant-derived photosensory module into the intracellular loop of an engineered ORAI1 channel. LOCa displays biophysical features reminiscent of the ORAI1 channel, which enables precise optical control over Ca 2+ signals and hallmark Ca 2+ -dependent physiological responses. Furthermore, we demonstrate the use of LOCa to modulate aberrant hematopoietic stem cell self-renewal, transcriptional programming, cell suicide, as well as neurodegeneration in a Drosophila model of amyloidosis. Existing optogenetic methods to induce calcium mobilisation lack selectivity and specificity. Here, the authors design and engineer a single-component light-operated calcium channel to provide optical control over calcium signals and calcium-dependent physiological responses: LOCa.

The application of current channelrhodopsin-based optogenetic tools is limited by the lack of strict ion selectivity and the inability to extend the spectra sensitivity into the near-infrared (NIR) tissue transmissible range. Here we present an NIR-stimulable optogenetic platform (termed 'Opto-CRAC') that selectively and remotely controls Ca2+ oscillations and Ca2+-responsive gene expression to regulate the function of non-excitable cells, including T lymphocytes, macrophages and dendritic cells. When coupled to upconversion nanoparticles, the optogenetic operation window is shifted from the visible range to NIR wavelengths to enable wireless photoactivation of Ca2+-dependent signaling and optogenetic modulation of immunoinflammatory responses. In a mouse model of melanoma by using ovalbumin as surrogate tumor antigen, Opto-CRAC has been shown to act as a genetically-encoded 'photoactivatable adjuvant' to improve antigen-specific immune responses to specifically destruct tumor cells. Our study represents a solid step forward towards the goal of achieving remote and wireless control of Ca2+-modulated activities with tailored function. Optogenetics is a technique that has been used to study nerve cells for several years. It involves genetically engineering these cells to produce proteins from light-sensitive bacteria, and results in nerve cells that will either send, or stop sending, nerve impulses when they are exposed to a particular color of light. Neuroscientists have learned a lot about brain circuits using the technique, and now researchers in many other fields are giving it a try. There are, however, several challenges to using optogenetics in other types of cells. Nerve cells create a tiny electrical impulses when they are activated, which helps them quickly transmit messages. But other types of cells use more diverse means to communicate and transmit signals. This means that optogenetics techniques must be adapted. Additionally, many cells are located deep in the body and so getting the light to them can be difficult. He, Zhang et al. have now developed an optogenetic system (termed “Opto-CRAC”) that can control immune cells buried deep in tissue. The action of immune cells can be tuned by controlling the flow of calcium ions through gate-like proteins in their membranes. He, Zhang et al. genetically engineered immune cells so that a calcium gate-controlling protein became light sensitive. When the cells were exposed to a blue light the calcium ion gates opened. When the light was turned off, the gates closed. More intense light caused more calcium to enter into the cells. Further experiments then revealed that exposing these engineered immune cells to blue light in the laboratory could trigger an immune response. The next obstacle was getting light to immune cells in a live animal. So, He, Zhang et al. used specific nanoparticles that have been shown to help transmit light deep within tissue. In these experiments, mice were injected with the light-sensitive immune cells and the nanoparticles. Then, a near-infrared laser beam that can transmit into the tissues was pointed at the mice. This caused calcium channels to open in the engineered cells deep in the mice. Finally, further experiments were used to show that this light-based stimulation could boost an immune response to aid the killing of cancer cells. Other scientists will likely use the technique to help them study immune, heart, and other types of cells that use calcium to communicate.

Through a proteomic analysis of ER–PM junctions, Zhou and colleagues and Wang and colleagues discover that the transmembrane protein STIMATE is a positive regulator of STIM localization and function, thereby stimulating Ca 2+ influx. Specialized junctional sites that connect the plasma membrane (PM) and endoplasmic reticulum (ER) play critical roles in controlling lipid metabolism and Ca 2+ signalling 1 , 2 , 3 , 4 . Store-operated Ca 2+ entry mediated by dynamic STIM1–ORAI1 coupling represents a classical molecular event occurring at ER–PM junctions, but the protein composition and how previously unrecognized protein regulators facilitate this process remain ill-defined. Using a combination of spatially restricted biotin labelling in situ coupled with mass spectrometry 5 , 6 and a secondary screen based on bimolecular fluorescence complementation 7 , we mapped the proteome of intact ER–PM junctions in living cells without disrupting their architectural integrity. Our approaches led to the discovery of an ER-resident multi-transmembrane protein that we call STIMATE ( STIM -activating enhancer, encoded by TMEM110 ) as a positive regulator of Ca 2+ influx in vertebrates. STIMATE physically interacts with STIM1 to promote STIM1 conformational switch. Genetic depletion of STIMATE substantially reduces STIM1 puncta formation at ER–PM junctions and suppresses the Ca 2+ –NFAT signalling. Our findings enable further genetic studies to elucidate the function of STIMATE in normal physiology and disease, and set the stage to uncover more uncharted functions of hitherto underexplored ER–PM junctions.

STIM1 and STIM2 are widely expressed endoplasmic reticulum (ER) Ca 2+ sensor proteins able to translocate within the ER membrane to physically couple with and gate plasma membrane Orai Ca 2+ channels. Although they are structurally similar, we reveal critical differences in the function of the short STIM-Orai-activating regions (SOAR) of STIM1 and STIM2. We narrow these differences in Orai1 gating to a strategically exposed phenylalanine residue (Phe-394) in SOAR1, which in SOAR2 is substituted by a leucine residue. Remarkably, in full-length STIM1, replacement of Phe-394 with the dimensionally similar but polar histidine head group prevents both Orai1 binding and gating, creating an Orai1 non-agonist. Thus, this residue is critical in tuning the efficacy of Orai activation. While STIM1 is a full Orai1-agonist, leucine-replacement of this crucial residue in STIM2 endows it with partial agonist properties, which may be critical for limiting Orai1 activation stemming from its enhanced sensitivity to store-depletion. STIM proteins are key regulators of intracellular Ca 2+ signalling. Here, Wang et al . demonstrate that subtle differences between STIM1 and its close homologue STIM2 have profound consequences for their ability to gate Orai1 Ca 2+ channels, thus revealing the basis for their distinct physiological functions.

Stromal interaction molecule 1 (STIM1) monitors ER-luminal Ca 2+ levels to maintain cellular Ca 2+ balance and to support Ca 2+ signalling. The prevailing view has been that STIM1 senses reduced ER Ca 2+ through dissociation of bound Ca 2+ from a single EF-hand site, which triggers a dramatic loss of secondary structure and dimerization of the STIM1 luminal domain. Here we find that the STIM1 luminal domain has 5–6 Ca 2+ -binding sites, that binding at these sites is energetically coupled to binding at the EF-hand site, and that Ca 2+ dissociation controls a switch to a second structured conformation of the luminal domain rather than protein unfolding. Importantly, the other luminal-domain Ca 2+ -binding sites interact with the EF-hand site to control physiological activation of STIM1 in cells. These findings fundamentally revise our understanding of physiological Ca 2+ sensing by STIM1, and highlight molecular mechanisms that govern the Ca 2+ threshold for activation and the steep Ca 2+ concentration dependence. Stromal interaction molecule 1 (STIM1) monitors ER-luminal Ca 2 +  levels to maintain cellular Ca 2 +  balance. Here the authors find that the STIM1 luminal domain monomer has multiple Ca 2 +  - binding sites which set the threshold for physiological activation of STIM1 in cells.

Production of melanin pigments is a protective mechanism of the skin against ultraviolet (UV)-induced damage and carcinogenesis. However, the molecular basis for melanogenesis is still poorly understood. Herein, we demonstrate a critical interplay between the primary cilium and the melanocortin 1 receptor (MC1R) signaling. Our data show that UV and α-melanocyte-stimulating hormone (α-MSH) trigger cilium formation in human melanocytes and melanoma cells. Deficiency of MC1R or the presence of its red hair color (RHC) variations significantly attenuates the UV/α-MSH-induced ciliogenesis. Further investigation reveals that MC1R enters the cilium upon UV/α-MSH stimulation, which is facilitated by the interaction of MC1R with the BBSome and the palmitoylation of MC1R. MC1R interacts with the BBSome through the second and third intercellular loops, which contain the common RHC variant alleles (R151C and R160W). These RHC variants of MC1R exhibit attenuated ciliary localization, and enforced ciliary localization of these variants elevates melanogenesis. Ciliary MC1R triggers a sustained cAMP signaling and selectively stimulates Sox9, which appears to up-regulate melanogenesis-related genes as the transcriptional cofactor for MITF. These findings reveal a previously unrecognized nexus between MC1R and cilia and suggest an important mechanism for RHC variant-related pigmentary defects.

Calcium signals, pivotal in controlling cell function, can be generated by calcium entry channels activated by plasma membrane depolarization or depletion of internal calcium stores. We reveal a regulatory link between these two channel subtypes mediated by the ubiquitous calcium-sensing STIM proteins. STIM1 activation by store depletion or mutational modification strongly suppresses voltage-operated calcium (CaV1.2) channels while activating store-operated Orai channels. Both actions are mediated by the short STIM-Orai activating region (SOAR) of STIM1. STIM1 interacts with CaV1.2 channels and localizes within discrete endoplasmic reticulum/plasma membrane junctions containing both CaV1.2 and Orai1 channels. Hence, STIM1 interacts with and reciprocally controls two major calcium channels hitherto thought to operate independently. Such coordinated control of the widely expressed CaV1.2 and Orai channels has major implications for Ca²⁺ signal generation in excitable and nonexcitable cells.

The Endoplasmic/sarcoplasmic reticulum (ER/SR) is central to calcium (Ca 2+ ) signaling, yet current genetically encoded Ca 2+ indicators (GECIs) cannot detect elementary Ca 2+ release events from ER/SR, particularly in muscle cells. Here, we report NEMOer, a set of organellar GECIs, to efficiently capture ER Ca 2+ dynamics with increased sensitivity and responsiveness. NEMOer indicators exhibit dynamic ranges an order of magnitude larger than G-CEPIA1er, enabling 2.7-fold more sensitive detection of Ca 2+ transients in both non-excitable and excitable cells. The ratiometric version further allows super-resolution monitoring of local ER Ca 2+ homeostasis and dynamics. Notably, NEMOer-f enabled the inaugural detection of Ca 2+ blinks, elementary Ca 2+ releasing signals from the SR of cardiomyocytes, as well as in vivo spontaneous SR Ca 2+ releases in zebrafish. In summary, the highly dynamic NEMOer sensors expand the repertoire of organellar Ca 2+ sensors that allow real-time monitoring of intricate Ca 2+ dynamics and homeostasis in live cells with high spatiotemporal resolution. The endoplasmic/sarcoplasmic reticulum (ER/SR) plays a crucial role in calcium signaling, but there are few methods capable of efficiently capturing ER/SR Ca 2+ dynamics. Here authors develop a set of genetically encoded indicators enabling ratiometric super-resolution imaging and detection of elementary Ca 2+ release in cardiomyocytes.