Acquisition of nonprofessional phagocytic cell fate plays an important role in sculpting functional metazoan organs and maintaining overall tissue homeostasis. Though physiologically highly relevant, how the normal epithelial cells acquire phagocytic fate is still mostly unclear. We have employed the Drosophila ovary model to demonstrate that the classical ecdysone signaling in the somatic epithelial

Lipid droplets (LDs) are ubiquitous neutral lipid storage organelles that form at discrete subdomains in the ER bilayer. The assembly of these ER subdomains and the mechanism by which proteins are recruited to them is poorly understood. Here, we investigate the spatiotemporal distribution of Pex30 at the ER-LD membrane contact sites (MCSs). Pex30, an ER membrane-shaping protein, has a reticulon homology

Centriolar satellites are cytoplasmic particles found in the vicinity of centrosomes and cilia whose specific functional contribution has long been unclear. Here, we identify Combover as the Drosophila ortholog of the main scaffolding component of satellites, PCM1. Like PCM1, Combover localizes to cytoplasmic foci containing centrosomal proteins and its depletion or mutation results in centrosomal

The highly conserved basement membrane protein collagen IV is stereotypically composed of two α1 subunits and one α2 subunit. In this issue, Srinivasan et al. (https://doi.org/10.1083/jcb.202412118) show that specific C. elegans basement membranes include collagen IV trimers with other compositions, suggesting a new diversity.

BNIP3 and NIX are the main receptors for mitophagy, but their mechanisms of action remain elusive. Here, we used correlative light EM (CLEM) and electron tomography to reveal the tight attachment of isolation membranes (IMs) to mitochondrial protrusions, often connected with ER via thin tubular and/or linear structures. In BNIP3/NIX-double knockout (DKO) HeLa cells, the ULK1 complex and nascent IM

The ATG9 transmembrane protein scrambles lipids to regulate phagophore formation during autophagy. Two recent studies from Peng et al. (https://doi.org/10.1083/jcb.202411092) and De Tito et al. (https://doi.org/10.1101/2024.07.23.604321) identify ATG9 as a conserved regulator of lysosome repair in Caenorhabditis elegans and human cells, but differences in repair mechanisms exist between these taxa

During animal cell cytokinesis, active RhoA assembles actomyosin-based contractile rings that tend to close asymmetrically. Through imaging C. elegans zygotes, Lebedev et al. (https://doi.org/10.1083/jcb.202405182) reveal that the scaffold protein, anillin, promotes asymmetric ring closure by locally sequestering RhoA from its canonical effectors and thereby limiting actomyosin contractility.

Cytokinesis, the final stage of cell division, serves to physically separate daughter cells. In cultured naïve mouse embryonic stem cells, cytokinesis lasts unusually long. Here, we describe a novel function for the kinesin-13 member KIF2A in this process. In genome-engineered mouse embryonic stem cells, we find that KIF2A localizes to spindle poles during metaphase and regulates spindle length in

Neurons release neurotransmitters from synaptic vesicles (SVs) and neuropeptides from dense-core vesicles (DCVs). The presynaptic proteins RIM and MUNC13 play key roles in both pathways. It remains unclear how DCVs are targeted to release sites and whether RIM and MUNC13 are involved in this process. Here, we show that three membrane-binding domains in RIM and MUNC13 regulate DCV exocytosis differently

In this issue, Jaffray and colleagues (https://doi.org/10.1083/jcb.202407133) detail the molecular machinery required to degrade the oncogene PML in response to arsenic treatment. Different posttranslational modifiers team up: ubiquitin, SUMO1, and -2/3, linked by the SUMO-targeted ubiquitin ligases TOPORS and RNF4.

Osteoclasts are multinucleated giant cells that are formed by the fusion of precursor cells. Cell-cell fusion is mediated by membrane protrusion driven by actin reorganization, but the role of membrane mechanics in this process is unknown. Utilizing live-cell imaging, optical tweezers, manipulation of membrane-to-cortex attachment (MCA), and genetic interference, we show that a decrease in plasma membrane

In animal cells, cleavage furrow formation is controlled by localized activation of the GTPase RhoA at the equatorial membrane using cues transmitted from the spindle. Here, we explore the function of LIN-5, a well-studied protein known for its role in aster separation and spindle positioning in cleavage furrow formation. We show that the cortical pool of LIN-5, recruited by GPR-1/2 and important for

Kinesin-1 walks along microtubules by alternating ATP hydrolysis and movement of its two motor domains ("head"). The detached head preferentially binds to the forward tubulin-binding site after ATP binds to the microtubule-bound head, but the mechanism preventing premature microtubule binding while the partner head awaits ATP remains unknown. Here, we examined the role of the neck linker, the segment

Basement membranes (BMs) are specialized extracellular matrix (ECM) structures essential for organ morphogenesis, architecture, and function. BM composition and properties vary between tissues, developmental stages, and disease states, and there is only a rudimentary understanding of BM dynamics. Here, we introduce a versatile mouse model carrying a multifunctional dual-color fluorescence tagged allele

Parkinson's disease results from degeneration of dopaminergic neurons in the midbrain, but the underlying mechanisms are unclear. Here, we identify novel crosstalk between depolarization-induced entry of Ca2+ and lysosomal cation release in maintaining dopaminergic neuronal function. The common disease-causing G2019S mutation in LRRK2 selectively exaggerated Ca2+ entry in vitro. Chemical and molecular

Kinesin motor proteins, vital for intracellular microtubule-based transport, display region-specific motility within cells, a phenomenon that remains molecularly enigmatic. This study focuses on the localized activation of OSM-3, an intraflagellar transport kinesin crucial for the assembly of ciliary distal segments in Caenorhabditis elegans sensory neurons. Fluorescence lifetime imaging microscopy

Mitochondrial function is critical for neuronal activity and systemic metabolic adaptation. In this issue, Li et al. (https://doi.org/10.1083/jcb.202408050) identify TMBIM-2 as a key regulator of calcium dynamics, coordinating the neuronal-to-intestinal mitochondrial unfolded protein response (UPRmt), pathogen-induced aversive learning, and aging.

Telomeres, the DNA-protein complex located at the ends of linear eukaryotic chromosomes, not only safeguard genetic information from DNA erosion and aberrant activation of the DNA damage response pathways but also play a pivotal role in sexual reproduction. During meiotic prophase I, telomeres attach to the nuclear envelope and migrate along its surface, facilitating two-dimensional DNA homology searches

During unilateral furrow ingression, one side of the cytokinetic ring (leading edge) ingresses before the opposite side (lagging edge). Anillin mediates unilateral furrowing during cytokinesis in the one-cell C. elegans zygote by limiting myosin II accumulation in the ring. Here, we address the role of anillin in this process and show that anillin inhibits not only the accumulation of myosin II but

Ribosome stalling during co-translational translocation at the ER causes translocon clogging and impairs ER protein biogenesis. Mammalian cells resolve translocon clogging via a poorly characterized translocation-associated quality control (TAQC) process. Here, we combine a genome-wide CRISPR screen with live-cell imaging to dissect the molecular linchpin of TAQC. We show that TAQC substrates translated

Primary cilium projects from cells to provide a communication platform with neighboring cells and the surrounding environment. This is ensured by the selective entry of membrane receptors and signaling molecules, producing fine-tuned and effective responses to the extracellular cues. In this study, we focused on one family of signaling molecules, the fibroblast growth factor receptors (FGFRs), their

Peroxisomes are integral metabolic organelles involved in both catabolic and anabolic processes in humans, with defects linked to diseases. The functions of peroxisomes are regulated at transcriptional, translational, and posttranslational levels. In this study, we employed the CRISPR/Cas9-based screening of a ubiquitin ligase library to identify regulators of human peroxisomes. We discovered that

The regulation of centrosome position is critical to the alignment of intracellular structures with extracellular cues. The exact nature and spatial distribution of the mechanical forces that balance at the centrosome are unknown. Here, we used laser-based nanoablations in adherent cells and found that forces along microtubules were damped by their anchoring to the actin network, rendering them ineffective

Arsenic effectively treats acute promyelocytic leukemia by inducing SUMO and ubiquitin-dependent degradation of the promyelocytic leukemia (PML)-retinoic acid receptor alpha oncogenic fusion protein. However, some patients relapse with arsenic-resistant disease because of missense mutations in PML. To determine the mechanistic basis for arsenic resistance, PML-/- cells were reconstituted with YFP fusions

TANGO2 deficiency in humans leads to progressive neurological impairment, punctuated by life-threatening metabolic crises. In this issue, Lujan and colleagues demonstrate that TANGO2 localizes within the mitochondrial lumen and binds acyl-CoA species, potentially implicating it as a lipid trafficking protein.

Selective autophagy targets specific cellular cargo for degradation. In this issue, Zhao et al. (https://doi.org/10.1083/jcb.202410150) uncovered that Rab GTPases serve as pivotal "autophagy cues" for recruitment of cargo receptors to facilitate mitophagy, lipophagy, and xenophagy, contributing to the precise spatiotemporal regulation of selective autophagy.

Circadian rhythm disorders are common characteristics of neurodegenerative diseases. The pathological aggregation of transactive response DNA-binding protein 43 (TDP-43) is associated with multiple neurodegenerative diseases, such as amyotrophic lateral sclerosis. However, the relationship between TDP-43 and circadian rhythm remains unknown. Here, we found that TDP-43 is rhythmically expressed both

Cyclins and cyclin-dependent kinases (CDKs) orchestrate key events in the cell cycle. However, the uniqueness of individual mitotic cyclins has been a long-standing puzzle. By rapidly removing cyclins in G2 human cells, we found that deficiency of B-type cyclins attenuates mitotic onset and uncouples the G2-M kinase network from mitosis, resulting in sustained activation of PLK1 and cyclin A-CDK1.

The transmembrane autophagy protein ATG9 has multiple functions essential for autophagosome formation. Here, we uncovered a novel function of ATG-9 in regulating lysosome biogenesis and integrity in Caenorhabditis elegans. Through a genetic screen, we identified that mutations attenuating the lipid scrambling activity of ATG-9 suppress the autophagy defect in epg-5 mutants, in which non-degradative

Selective autophagy plays a crucial role in maintaining cellular homeostasis by specifically targeting unwanted cargo labeled with "autophagy cues" signals for autophagic degradation. In this study, we identify Rab GTPases as a class of such autophagy cues signals involved in selective autophagy. Through biochemical and imaging screens, we reveal that human Rab GTPases are common autophagy substrates

Protein aggregates are degraded by both the autophagy-lysosomal and the ubiquitin-proteasome pathways. Macroautophagy and microautophagy, two forms of the autophagy-lysosomal pathway, are widely conserved across eukaryotes. While macroautophagy has been extensively studied in the context of degradation of protein aggregates, microautophagy remains less explored. Here, we identify the UBAP1-containing

We explored how the number of structures is determined in an intracellular organelle series. In Tetrahymena, the oral apparatus contains three diagonal ciliary rows: M1, M2, and M3. During development, the M rows emerge by sequential segmentation of a group of basal bodies, starting with the longest and most anterior M1 and ending with the shortest and most posterior M3. The mpD-1 and mpH-1 alleles

The nanoscale organization of proteins within synapses is critical for maintaining and regulating synaptic transmission and plasticity. Here, we used cryo-electron tomography (cryo-ET) to directly visualize the three-dimensional architecture and supramolecular organization of postsynaptic components in both synaptosomes and synapses from cultured neurons. Cryo-ET revealed that postsynaptic density

Mutations or ablation of Snx10 are associated with neurodegeneration, blindness, and osteopetrosis. The similarities between osteoclasts and macrophages prompted us to analyze the role of Snx10 in phagocytosis. Deletion of Snx10 impaired phagosome resolution. Defective resolution was caused by reduced Cl- accumulation within (phago)lysosomes, replicating the phenotype reported in macrophages lacking

Phosphatidylinositol (PI) 3,5-bisphosphate (PI(3,5)P2) is a minor inositol-containing phospholipid that serves as an important regulator of endolysosomal functions. However, the precise sites of subcellular enrichment and molecular targets of this regulatory lipid are poorly understood. Here, we describe the generation and detailed characterization of a short engineered catalytic fragment of the human

Under endoplasmic reticulum (ER) stress (ERS), cells initiate the unfolded protein response (UPR) to maintain ER homeostasis. Recent studies revealed ERS transmission between cells and tissues, by activating the cell-nonautonomous UPR in cells that do not experience ERS directly. Here, we report that ERS triggers a rapid release of ceramide independent of the UPR, but requiring the acid sphingomyelinase

GPCRs comprise the largest family of signaling receptors and control essentially every physiological process. Many biochemical reactions underlying GPCR signaling are now elucidated to atomic resolution in cell-free preparations, but how elemental signaling reactions are organized in intact cells remains less clear. Significant progress has been made toward bridging this knowledge gap by leveraging

Neutrophils are highly motile leukocytes that migrate inside tissues to destroy invading pathogens. Ca2+ signals coordinate leukocytes migration, but whether Ca2+ fluxes mediated by Stim proteins at ER-PM contact sites regulate neutrophil actin-based motility is unclear. Here, we show that myeloid-specific Stim1/2 ablation decreases basal cytosolic Ca2+ levels and prevents adhesion-induced Ca2+ elevations

Schwann cells, the myelinating glia of the peripheral nervous system (PNS), are critical for myelin development, maintenance, and repair. Rac1 is a known regulator of radial sorting, a key step in developmental myelination. Previously, in zebrafish, we showed that the loss of Dock1, a Rac1-specific guanine nucleotide exchange factor, resulted in delayed peripheral myelination during development. Here

Neuronal mitochondrial function is critical for orchestrating inter-tissue communication essential for overall fitness. Despite its significance, the molecular mechanism underlying the impact of prolonged mitochondrial stresses on neuronal activity and how they orchestrate metabolism and aging remains elusive. Here, we identified the evolutionarily conserved transmembrane protein XBX-6/TMBIM-2 as a

Bhattacharyya and Klumpp discuss exciting new observations of the native intermediate filament network in cells shown in Renganathan et al. (https://doi.org/10.1083/jcb.202406054) in this issue. Combining two powerful imaging techniques, Renganathan et al. examine the organization and dynamics of vimentin filaments in unprecedented detail.

The type IV collagen triple helix, composed of three ⍺-chains, is a core basement membrane (BM) component that assembles into a network within BMs. Endogenous tagging of all ⍺-chains with genetically encoded fluorophores has remained elusive, limiting our understanding of this crucial BM component. Through genome editing, we show that the C termini of the C. elegans type IV collagen ⍺-chains EMB-9

Multivesicular bodies (MVBs) are crucial for membrane protein degradation and lipid homeostasis. A recent study by Gao and colleagues (https://doi.org/10.1083/jcb.202410013) identifies Any1 as a phospholipid scramblase that plays an important role in MVB biogenesis by coordinating membrane remodeling with lipid transfer through Vps13 at organelle contact sites.

Proteostasis involves degradation and recycling of proteins from organelles, membranes, and multiprotein complexes. These processes can depend on protein extraction and unfolding by the essential mechanoenzyme valosin-containing protein (VCP) and on ubiquitin chain remodeling by ubiquitin-specific proteases known as deubiquitinases (DUBs). How the activities of VCP and DUBs are coordinated is poorly

Stress-activated protein kinases (SAPKs) respond to a wide variety of stressors. In most cases, the pathways through which specific stress signals are transmitted to the SAPK are not known. We show that the yeast SAPK Hog1 is activated by acetic acid through an intracellular mechanism that does not involve stimulation of the high osmolarity glycerol (HOG) signaling pathway beyond its basal level. Rather

The autophagy-lysosomal system comprises a highly dynamic and interconnected vesicular network that plays a central role in maintaining proteostasis and cellular homeostasis. In this study, we uncovered the deubiquitinating enzyme (DUB), dUsp45/USP45, as a key player in regulating autophagy and lysosomal activity in Drosophila and mammalian cells. Loss of dUsp45/USP45 results in autophagy activation

Vimentin intermediate filaments (VIFs) form complex, tightly packed networks; due to this density, traditional imaging approaches cannot discern single-filament behavior. To address this, we developed and validated a sparse vimentin-SunTag labeling strategy, enabling single-particle tracking of individual VIFs and providing a sensitive, unbiased, and quantitative method for measuring global VIF motility

Organelle biogenesis is fundamental to eukaryotic cell biology. Yeast signaling endosomes were recently identified as a signaling platform for the evolutionarily conserved Target of Rapamycin Complex 1 (TORC1) kinase complex. Despite the importance of signaling endosomes for TORC1-mediated control of cellular metabolism, how this organelle is generated has been a mystery. Here, we developed a system

Endosomes are central organelles in the recycling and degradation of receptors and membrane proteins. Once endocytosed, such proteins are sorted at endosomes into intraluminal vesicles (ILVs). The resulting multivesicular bodies (MVBs) then fuse with the lysosomes, leading to the degradation of ILVs and recycling of the resulting monomers. However, the biogenesis of MVBs requires a constant lipid supply

Membrane contact sites (MCS) between the plasma membrane (PM) and endoplasmic reticulum (ER) regulate Ca2+ influx. However, the mechanisms by which cells modulate ER-PM MCS density are not understood, and the role of Ca2+, if any, in regulating these is unknown. We report that in Drosophila photoreceptors, MCS density is regulated by the Ca2+ channels, TRP and TRPL. Regulation of MCS density by Ca2+

Legionella pneumophila is an intracellular bacterial pathogen that modulates membrane trafficking to survive and proliferate within host cells. After phagocytosis, the L. pneumophila-containing vacuole evades the endocytic pathway by excluding the host GTPase Rab5, a crucial regulator of phagosomal maturation. In this study, we show that the evolutionarily conserved lysine residue K134 of Rab5 undergoes

Compartment for unconventional protein secretion (CUPS), a compartment for secretion of signal sequence-lacking proteins, forms through COPI-independent extraction of membranes from early Golgi cisternae, lacks Golgi-specific glycosyltransferases, and requires phosphatidylinositol 4-phosphate (PI4P) for biogenesis, as well as phosphatidylinositol 3-phosphate for stability. Our findings demonstrate

Loss of TANGO2 in humans precipitates metabolic crises during periods of heightened energy demand, such as fasting, infections, or high fever. TANGO2 has been implicated in various functions, including lipid metabolism and heme transport, and its cellular localization remains uncertain. In our study, we demonstrate that TANGO2 localizes to the mitochondrial lumen via a structural region containing

In this issue, El Mossadeq et al. (https://doi.org/10.1083/jcb.202403125) report that a structure forms around segregating chromosomes following meiosis I that shares features with the nuclear envelope in interphase but also has distinct, unique characteristics.

Post-Golgi exocytic trafficking, fundamental for secretion and cell surface component integration, remains incompletely understood at the molecular level. Here, we investigated this process using Caenorhabditis elegans and mammalian cell models, revealing a novel exocytic carrier capturing mechanism involving the small GTPase RAB-10/Rab10 and its effector EHBP-1/EHBP1. EHBP-1, localized in recycling

Rickettsia are bacterial pathogens known for their actin-based motility in the host cell cytoplasm. In this issue, Acevedo-Sánchez and colleagues (https://doi.org/10.1083/jcb.202406122) discover non-motile Rickettsia bacteria hijack host machinery to form stable membrane contact sites with the host endoplasmic reticulum.

In this issue, Lessenger and colleagues (https://doi.org/10.1083/jcb.202403154) investigate why certain differentiated tissues require extremely high DNA content. Using the nematode worm Caenorhabditis elegans, they show that restricting genome copies in intestinal cells triggers compensatory gene expression adaptations, which maintain organismal fitness at the expense of offspring vitality.

Vacuolar protein sorting 41 (VPS41), a component of the homotypic fusion and protein sorting (HOPS) complex for lysosomal fusion, is essential for the trafficking of lysosomal membrane proteins via lysosome-associated membrane protein (LAMP) carriers from the trans-Golgi network (TGN) to endo/lysosomes. However, the molecular mechanisms underlying this pathway and VPS41's role herein remain poorly

Sphingolipids serve as building blocks of membranes to ensure subcellular compartmentalization and facilitate intercellular communication. How cell type-specific lipid compositions are achieved and what is their functional significance in tissue morphogenesis and maintenance has remained unclear. Here, we identify a stem cell-specific role for ceramide synthase 4 (CerS4) in orchestrating fate decisions

Mitochondrial retrograde signaling (MRS) pathways relay the functional status of mitochondria to elicit homeostatic or adaptive changes in nuclear gene expression. Budding yeast have "intergenomic signaling" pathways that sense the amount of mitochondrial DNA (mtDNA) independently of oxidative phosphorylation (OXPHOS), the primary function of genes encoded by mtDNA. However, MRS pathways that sense