Cell最新文献

The guanosine triphosphate (GTP)-bound state of the heterodimeric Rag GTPases functions as a molecular switch regulating mechanistic target of rapamycin complex 1 (mTORC1) activation at the lysosome downstream of amino acid fluctuations. Under low amino acid conditions, GTPase-activating protein (GAP) activity toward Rags 1 (GATOR1) promotes RagA GTP hydrolysis, preventing mTORC1 activation. KICSTOR recruits and regulates GATOR1 at the lysosome by undefined mechanisms. Here, we resolve the KICSTOR-GATOR1 structure, revealing a striking ∼60-nm crescent-shaped assembly. GATOR1 anchors to KICSTOR via an extensive interface, and mutations that disrupt this interaction impair mTORC1 regulation. The S-adenosylmethionine sensor SAMTOR binds KICSTOR in a manner incompatible with metabolite binding, providing structural insight into methionine sensing via SAMTOR-KICSTOR association. We discover that KICSTOR and GATOR1 form a dimeric supercomplex. This assembly restricts GATOR1 to an orientation that favors the low-affinity active GAP mode of Rag GTPase engagement while sterically restricting access to the high-affinity inhibitory mode, consistent with a model of an active lysosomal GATOR1 docking complex.

Efficient and precise delivery of therapeutics toward target loci of organs is crucial for effective disease therapy. However, conventional devices face remarkable challenges to achieve clinically desirable conformality, spatial controllability, and efficiency, especially to organs with complex anatomies, due to a lack of appropriate mechanical and/or material properties. Here, we report a bioelectronic patch for organ-conformal, kirigami-structured electro-transfection (POCKET) that features high conformality enabled by parametric customization, achieving a theoretically maximum effective coverage area over the target organ. The four-layered POCKET forms a unique nanopore-cell juxtaposition configuration at the tissue-device interface, which induces precise, uniform electro-perforation while expediting intracellular transport of payloads. The high delivery efficiency and precise spatial controllability have been systematically validated with various organs. POCKET-mediated therapeutic delivery achieved organ protection from accumulated DNA damage or ischemia-reperfusion injury, restoring organ functionalities. This work presents a customizable technique with translational value for precise therapy in challenging target organs.

The human gut is a dynamic environment, where changes in pH, oxygen, and osmolality influence microbiota composition and disease. Monitoring these environmental shifts is crucial for advancing gut health diagnostics and therapeutics, yet non-invasive monitoring tools remain limited. Genetically tractable commensals, including Bacteroides thetaiotaomicron, offer promising chassis for engineering biosensors but lack modular systems for precise sensing and reporting. Here, we developed genetic tools for B. thetaiotaomicron, including (1) repressible promoters for tunable fluorescent protein expression, (2) a DNA-based system to modulate repressor activity, (3) a modular, fluorescence-based transcriptional reporter circuit, and (4) an alternative plasmid integration mode. Using these components, we engineered biosensors to detect increased gut osmolality caused by malabsorption and validated them in vitro and in a murine model of laxative-induced osmotic diarrhea. These biosensors enabled long-term, non-invasive reporting of gut osmolality from single-cell fluorescence, demonstrating the potential of gut bacteria as monitoring platforms in gut health applications.

Many proteins localize in membraneless organelles. However, understanding the steps along membraneless organelle formation-and the structural impact on granule constituents-has been hindered by limited resolution of intracellular data. We address these challenges through in situ cryo-electron tomography (cryo-ET) along with formation of yeast proteasome storage granules (PSGs). During the transition from proliferation to quiescence, doubly capped 26S proteasomes arrested in an inactive state arrange into ∼7.5 MDa trimeric units, dispersed in the nucleoplasm and congregated along the nuclear envelope near the nuclear pore. 9-Å-resolution cryo-ET structures reveal that cytoplasmic PSGs formed in various energy-limiting conditions are paracrystalline arrays of bundled fibers, assembled from stacking of proteasome trimers. The paracrystalline arrangement maintains a pool of fully assembled inactive 26S proteasomes that are released in energy-rich conditions. Overall, our data reveal structural steps along the assembly of an intracellular membraneless organelle in situ and quinary structure formation controlling a major eukaryotic regulatory machine.

Although ATP-independent chaperones assist RNA folding, the mechanisms by which they function remain elusive. Here, we demonstrate how two RNA chaperones collaborate to unfold misfolded noncoding RNAs (ncRNAs). The ring-shaped Ro60 protein binds the ends of misfolded ncRNAs in its cavity, whereas La stabilizes nascent ncRNAs and assists their folding. Using cryo-electron microscopy to resolve the structure of a misfolded RNA complexed with Ro60 and La, we show that La cradles the Ro60 ribonucleoprotein (RNP), with its N-terminal domain binding the RNA 3' end after it passes through the Ro60 cavity, while its C-terminal domain destabilizes structures in the misfolded RNA body. Using selective 2'-hydroxyl acylation analyzed by primer extension and mutational profiling (SHAPE-MaP), we show that La and Ro60 function synergistically to unfold non-native structures. As the RNAs bound by Ro60 and La include both ncRNA precursors and ncRNAs with oligouridine tails, this RNA chaperone machine may function widely to recognize misfolded and otherwise aberrant ncRNAs and assist their unfolding.

Ferroptosis is a tumor-suppressive mechanism with therapeutic potential. While canonical ferroptosis is usually triggered by inducers, such as erastin and RSL-3, or by glutathione peroxidase (GPX)4 loss, how ferroptosis occurs naturally in vivo without these triggers has been unclear. Building on evidence that p53 can mediate ferroptosis as a natural tumor-suppressive pathway, we describe a noncanonical, in vivo ferroptosis driven by reactive oxygen species (ROS)-induced phosphatidic acid (PA) peroxidation that proceeds without inducers. We identify GPX1 as a key regulator of this ROS-induced ferroptosis by modulating PA peroxidation. GPX1's effects depend on OSBPL8, an endoplasmic reticulum (ER)-membrane-associated oxysterol-binding protein. ROS-driven lipid peroxidation accumulates at the ER before plasma membrane rupture and cell death; GPX1 is recruited to the ER via OSBPL8 and directly reduces oxidized PA. OSBPL8 and GPX1 are overexpressed in cancers; knockdown of either promotes ROS-induced ferroptosis and suppresses tumor growth. Our data link the GPX1-OSBPL8 axis to in vivo ferroptosis and tumor suppression.

Rooted in place, plants must continuously respond and adapt to their ever-changing environment to survive, especially as climate change intensifies. Calcium ions (Ca²⁺) play a central role in plant responses to both biotic and abiotic challenges. Ca²⁺ signaling involves the coordinated action of channels and transporters that generate specific "Ca²⁺ codes," along with Ca²⁺-binding proteins that act as sensors to decode them. Studies over the past several decades have explored the molecular components that form the toolkit, pathways, and networks for the coding and decoding of Ca²⁺ signals in plants. This review focuses on the emerging mechanisms of calcium signaling in plants, beginning with an overview of the universal conceptual framework that governs the coding and decoding of Ca²⁺ signals, followed by examples of pathways in plant growth and reproduction, responses to abiotic stress and microbes, and systemic signaling in plants.