bims-pideca 2026-06-21 papers

bims-pideca

Biomed News

on Class IA PI3K signalling in development and cancer

Issue of 2026–06–21
sixteen papers selected by
Ralitsa Radostinova Madsen, MRC-PPU

Human vein-to-artery endothelial cell fate transition is driven by VEGF/ERK activation and PI3K inhibition.
Aging, Dauer, and Stature Phenotypes Are Conferred by Structure-Directed Missense Mutations in the Endogenous AGE-1/Phosphatidylinositol 3-Kinase Catalytic Subunit.
Distinct ERK and PI3K dependencies mediate a heterogeneous response to RAS(ON) inhibition in KRAS-mutant colorectal cancer.
Inactive β1-integrin acts as a junctional scaffold for angiopoietin/TIE2/FOXO1 signaling.
Pictilisib and nutrient stress synergize to induce methuosis via PI(4,5)P2-dependent macropinocytic dysregulation in cancer cells.
A human induced pluripotent stem cell model for the holistic study of epithelial-to-mesenchymal transitions.
Substrate selectivity as a paradigm shift in mTORC1 signaling.
Mitotic Cdc42 waves encode PI(3,4)P2 signaling and Golgi morphological state to control spindle scaling.
Chemigenetic fluorescent biosensors in biological imaging - New trends and advances.
Messenger RNA-encoded reporters for monitoring cellular stress and bioenergetics.
Structural basis of Drosophila insulin receptor activation by DILP2 hormone.
Spheroid construction using iPS cell-derived mesenchymal stem and endothelial cells.
Fibroblast adipogenesis restricts hemangioma growth through a PPARγ/Hippo-YAP/TAZ axis that promotes endothelial apoptosis and cell cycle arrest.
Optineurin, an autophagy adaptor, stabilizes Rictor to maintain Akt/mTOR signaling and antigen presentation.
Single-cell RNA sequencing profiles drug activity within spatially engineered 3D cultures.
VEGFR2 inhibition potentiates STING-mediated antitumor immunity.

Development. 2026 Jun 15. pii: dev.205490. [Epub ahead of print]

Human vein-to-artery endothelial cell fate transition is driven by VEGF/ERK activation and PI3K inhibition.

Z Amir Ugokwe, A L Pyke, E Trimm, M Chakraborty, X Fan, Ang Lay Teng, K M Loh, K Red-Horse.

  Artery endothelial cells (ECs) arise through different pathways, including differentiation from mesodermal cells (vasculogenesis) or from already established vein or capillary plexus ECs (angiogenesis), the latter being most common during embryonic development and regeneration. Understanding the vein-to-artery (v2a) transition could improve revascularization therapies, but progress is limited by a lack of human models. Here, we develop a human pluripotent stem cell (hPSC) differentiation protocol that models the v2a EC conversion. Comparing v2a and mesoderm-to-artery (m2a) transcriptomes with publicly available single cell RNA sequencing (scRNA-seq) data from human embryos showed they reflected angiogenesis- and vasculogenesis-derived artery ECs, respectively. This reductionist system revealed that VEGF activation alongside PI3K inhibition was sufficient for vein ECs to acquire arterial identity within 48 hours. We model a critical step in vascular development and define the minimal signals required for artery differentiation from veins, providing a framework to promote this conversion in revascularization or therapeutic contexts.

Keywords:  Angiogenesis; Cell fate switch; Endothelial differentiation; Human pluripotent stem cells; Vasculogenesis; Vein-to-artery endothelial conversion

DOI:  https://doi.org/10.1242/dev.205490
Aging Cell. 2026 Jun;25(6): e70571

Aging, Dauer, and Stature Phenotypes Are Conferred by Structure-Directed Missense Mutations in the Endogenous AGE-1/Phosphatidylinositol 3-Kinase Catalytic Subunit.

You Wu, Tam Duong, Neal R Rasmussen, Kent L Rossman, David J Reiner.

  Phosphatidylinositol 3-kinase (PI3K) integrates insulin/IGF signaling (IIS) and Ras inputs to control lifespan, metabolism and growth. Yet the organismal consequences of selective structural perturbations remain poorly understood. Using structure-guided CRISPR/Cas9-dependent genome editing, we dissected functions of AGE-1, the sole Class IA PI3K catalytic subunit in Caenorhabditis elegans. An endogenously tagged AGE-1, containing a long flexible linker, epitope and fluorescent tag, retained full activity, enabling visualization of native protein dynamics in vivo. A likely constitutively activating E630K substitution, modeled on oncogenic p110α alleles, markedly shortened lifespan and enhanced Ras-dependent induction of primary vulval precursor cell (VPC) fate, confirming evolutionary conservation of PI3K activation mechanisms that directly modulate longevity and development. Structural modeling further guided mutation of AGE-1 residues predicted to mediate Ras binding. Surprisingly, a putative AGE-1 variant defective in Ras association, together with a complementary Ras effector-binding mutation, produced enlarged animals with reduced dauer formation. These phenotypes reveal a previously unrecognized Ras>PI3K signaling axis that restrains somatic growth and promotes entry into diapause, counter to canonical IIS models. Together, these structure-informed alleles show that discrete PI3K structural perturbations can differentially uncouple lifespan, growth, and developmental outcomes in vivo. By combining structural modeling with genome editing in a tractable aging model, this work establishes a framework for dissecting conserved signaling enzymes at single-residue resolution and uncovers unexpected organismal roles for PI3K structure in coordinating growth and longevity.

Keywords:  AGE‐1; LET‐60/Ras; aging; animal size; dauer diapause; lifespan; phosphatidylinositol 3‐kinase; vulval precursor cells

DOI:  https://doi.org/10.1111/acel.70571
Cell Rep. 2026 Jun 18. pii: S2211-1247(26)00637-6. [Epub ahead of print]45(7): 117559

Distinct ERK and PI3K dependencies mediate a heterogeneous response to RAS(ON) inhibition in KRAS-mutant colorectal cancer.

Philip H Choi, Julia Meredith, Malvika Sharma, Xiaoping Chen, Juan Qiu, Vladimir Markov, Elisa de Stanchina, Mallika Singh, Neal Rosen.

  RAS inhibitors have demonstrated limited efficacy in KRAS-mutant colorectal cancer (CRC). Here, we evaluate RMC-7977, a RAS(ON) multi-selective inhibitor, which shows a heterogeneous response in a panel of preclinical CRC models. Inhibition of PI3K signaling and cyclin D1 (CCND1) expression are strongly correlated with response. We find that stratifying tumors based on the ERK dependence of cyclin D1, mediated by variability in CCND1 mRNA regulation, reveals two distinct resistance mechanisms. PI3K signaling plays a key role in driving persistent cyclin D1 expression in the less ERK-dependent tumors, and concurrent inhibition of RAS and PI3K can synergistically cause cell cycle arrest and promote apoptosis. However, in tumors with strongly ERK-dependent cyclin D1, vertical inhibition of RAS and MEK prevents feedback re-activation of the MAPK/ERK pathway and is more effective. In summary, we identify cyclin D1 as an important integrator and functional readout of upstream signaling that can inform optimal combination strategies for KRAS-mutant CRC.

Keywords:  CDK4/6; CP: cancer; KRAS; MEK; PI3K; apoptosis; cell cycle; colorectal cancer; cyclin D1; mTOR

DOI:  https://doi.org/10.1016/j.celrep.2026.117559
J Clin Invest. 2026 06 15. pii: e190552. [Epub ahead of print]136(12):

Inactive β1-integrin acts as a junctional scaffold for angiopoietin/TIE2/FOXO1 signaling.

Tuomas Sipilä, Srinivas Kumar Ponna, Abhinandan Venkatesha Murthy, Anne Pink, Giray Enkavi, Shraman Kumar Bohra, Klaudia Lewna, Keerthana Ganesh, Qina Liu, Mirka Korhonen, Tommi Kajander, Michael Potente, Johanna Ivaska, Ilpo Vattulainen, Veli-Matti Leppänen, Pipsa Saharinen.

  The blood and lymphatic vascular systems are regulated by angiopoietin (ANGPT) growth factors, which signal via endothelial TIE receptor tyrosine kinases and integrins. However, mechanistic understanding of how these receptors crosstalk is limited. Here, we show how β1-integrin inactivation regulates endothelial ANGPT/TIE2 signaling. By integrating biophysical analyses, X-ray crystallography, size-exclusion chromatography-small-angle X-ray scattering and atomistic molecular dynamics simulations, we show that ANGPT2 binds through its asymmetrically positioned C-terminal fibrinogen-like domains to both TIE2 and α5β1-integrin, forming a trimeric complex compatible with the inactive α5β1-integrin conformation. Inactive β1-integrin colocalizes with ANGPT-induced TIE2 in cell-cell junctions and stabilizing β1-integrin in its inactive state enhances junctional TIE2 accumulation and promotes nuclear exclusion of the TIE2 transcriptional effector FOXO1 in cultured endothelial cells. Endothelial-specific β1-integrin deletion in adult mice reduces venous TIE2 phosphorylation, whereas endotoxemia diminishes junctional β1-integrin along with decreased phosphorylated TIE2. In contrast, without TIE2, ANGPT2 uniquely engages active β1-integrin, via its N-terminal superclustering domain. Altogether, our results provide structural and mechanistic evidence of ANGPT signaling via α5β1-integrin and support a model in which inactive α5β1-integrin acts as a junctional scaffold for ANGPT/TIE2/FOXO1 signaling, explaining how integrin conformational switching spatially organizes growth factor signaling in the endothelium.

Keywords:  Angiogenesis; Cell biology; Growth factors; Integrins; Vascular biology

DOI:  https://doi.org/10.1172/JCI190552
Cell Death Dis. 2026 Jun 16.

Pictilisib and nutrient stress synergize to induce methuosis via PI(4,5)P2-dependent macropinocytic dysregulation in cancer cells.

Xuefei Wang, Xiaolin Sang, Yuemei Wen, Xingming Liao, Jiao Liu, Tiezheng Zheng, Tianming Xing, Min Wang, Dong An, Xining Zhang, Xiuling Li, Xinmiao Liang, Pixu Liu, Hailing Cheng.

Aberrant phosphatidylinositol 3-kinase (PI3K) activation drives many cancers, but PI3K inhibitors like Pictilisib often induce cytostasis rather than cytotoxicity, limiting their therapeutic potential. Here we demonstrate that PI3K inhibition combined with nutrient stress triggers methuosis, a non-apoptotic form of programmed cell death characterized by dysregulated macropinosomes. This response occurs selectively in PI3K-aberrant cancer cells that maintain macropinocytic uptake despite PI3K inhibition. Methuosis-associated vacuoles originate from macropinosomes that retain endosomal markers but fail to undergo lysosomal fusion. Active macropinocytic uptake is essential for methuosis, as demonstrated by suppression with EIPA and Bafilomycin A1, whereas the AKT inhibitor MK2206 has no effect, establishing that direct PI3K inhibition, rather than AKT signaling, is required. Mechanistically, PI3K blockade prevents conversion of phosphatidylinositol (4,5)-bisphosphate (PI(4,5)P2) to phosphatidylinositol (3,4,5)-trisphosphate (PI(3,4,5)P3) causing PI(4,5)P2 to accumulate on internalizing macropinosomal membranes. This aberrant PI(4,5)P2 enrichment impairs ion channel function across multiple channel families, disrupting intracellular osmotic balance. Ion dysregulation triggers aquaporin-1-mediated water influx, driving catastrophic vacuolar expansion and cell death. Although Pictilisib activates pro-survival autophagy, this fails to prevent methuosis-mediated cytotoxicity. In xenograft models, dietary restriction synergizes with Pictilisib to suppress tumor growth, correlating with pronounced intratumoral vacuolization. These findings reveal that combining PI3K inhibition with nutrient restriction converts cytostatic responses into methuosis-driven cytotoxicity via PI(4,5)P2-dependent macropinocytic dysregulation, providing a rational pharmacologic-dietary strategy to enhance PI3K-targeted cancer efficacy.

DOI: https://doi.org/10.1038/s41419-026-08994-6
Nat Methods. 2026 Jun 15.

A human induced pluripotent stem cell model for the holistic study of epithelial-to-mesenchymal transitions.

Caroline Hookway, Antoine Borensztejn, Leigh K Harris, Tiffany Barszczewski, Sara Carlson, Gokhan Dalgin, Suraj Mishra, Ellen M Adams, Julie C Dixon, Renske J Dupar, Jacqueline H Edmonds, Erik A Ehlers, Alexandra J Ferrante, Margaret A Fuqua, Clare R Gamlin, Philip Garrison, Janani Gopalan, Benjamin W Gregor, Maxwell J Hedayati, Victoria L Hurless, Kyle N Klein, Chantelle L Leveille, Sean L Meharry, Ricardo Mercado, Haley S Morris, Gouthamrajan Nadarajan, Nivedita Nivedita, Sandra A Oluoch, Serge E Parent, Amber Phan, Brock Roberts, Ashwin Samudre, Emmanuel E Sanchez, M Filip Sluzewski, Lev S Snyder, Derek J Thirstrup, Hannah F Thorp, John Paul Thottam, Julia R Torvi, Gaea Turman, Matheus P Viana, Lyndsay Wilhelm, Chamari S Wijesooriya, Jie Yao, Julie A Theriot, Ruwanthi N Gunawardane, Susanne M Rafelski.

The epithelial-to-mesenchymal transition (EMT) is a widely studied cell state change, yet differences in model design and measurement approaches limit comparison across studies. Addressing this challenge requires experimental model systems and analysis frameworks that support standardization across contexts. Here, we show that human induced pluripotent stem (hiPS) cells in defined cell culture geometries, two-dimensional colonies and three-dimensional lumenoids, enable multimodal measurements of EMT dynamics within a single experimental platform. Using fixed-cell and live-cell image-based assays, we quantify changes in cell migration, EMT-related molecular markers, cell-cell junction organization and interactions with the basement membrane, a specialized form of the extracellular matrix, during EMT induced in hiPS cells. We identify cell culture geometry-dependent differences in the timing of migration onset and show that basement membrane integrity can be quantitatively linked to these differences. Together, these results establish an imaging-based framework for analysis of cell state transitions and provide accessible datasets and tools.

DOI: https://doi.org/10.1038/s41592-026-03096-9
Curr Opin Cell Biol. 2026 Jun 17. pii: S0955-0674(26)00052-9. [Epub ahead of print]101 102664

Substrate selectivity as a paradigm shift in mTORC1 signaling.

Jiyoung Pan, Stephanie A Fernandes, Riko Hatakeyama, Constantinos Demetriades.

mTORC1 is a central regulator of cell growth and metabolism, classically viewed as a binary switch that promotes anabolic programs while suppressing catabolic pathways. Recent work advances this simplified model by revealing that mTORC1 signaling is highly substrate-specific, with distinct classes of substrates differentially regulated according to their modes of recruitment and subcellular localization. In this review, we discuss emerging evidence demonstrating that mTORC1 activity and its lysosomal localization can be functionally uncoupled, enabling selective phosphorylation of lysosomal versus non-lysosomal targets. We highlight how upstream regulatory pathways and post-translational modifications shape these substrate-specific outputs, and consider the implications of downstream uncoupling for the fundamental understanding of mTORC1 biology as well as human health and disease.

DOI: https://doi.org/10.1016/j.ceb.2026.102664
Sci Adv. 2026 Jun 19. 12(25): eaec7705

Mitotic Cdc42 waves encode PI(3,4)P2 signaling and Golgi morphological state to control spindle scaling.

Suet Yin Sarah Fung, Shengping Xiao, Yujin Bao, Morven Graham, Maohan Su, Xinran Liu, Joerg Bewersdorf, Min Wu.

Self-organizing waves are observed in numerous biological systems and may encode spatial and temporal information for cellular organization in the absence of prepatterns. In mitotic mast cells, periodic cortical waves emerge before spindle assembly with wave periods that are proportional to cell size. Here, we investigate the mechanisms that govern cortical wave scaling and examine the consequence of wave perturbation on mitotic spindle size scaling. We find that the periods of mitotic waves are regulated by the turnover of phosphatidylinositol 3,4-bisphosphate [PI(3,4)P2] on the plasma membrane, which depends on inositol polyphosphate-4-phosphatase type II (INPP4B). Genetic depletion of INPP4B increases cortical wave period and spindle length. Intriguingly, we observed mitotic wave periods that tunes continuously during mitosis, indicating the existence of a fast, posttranslational regulatory mechanism for wave scaling. We further find that the regulation of mitotic waves on the plasma membrane is controlled by the sequestering of INPP4B and PI(3,4)P2 upon mitotic Golgi fragmentation. On the basis of these findings, we propose a cell size-sensing mechanism in which cortical waves act like sonar waves, adjusting their timing and propagation based on the shuttling of signaling proteins between the cell cortex and intracellular organelles. This rapid communication scheme allows the cell to adjust spindle scaling dynamically, ensuring accurate cell division.

DOI: https://doi.org/10.1126/sciadv.aec7705
Curr Opin Chem Biol. 2026 Jun 17. pii: S1367-5931(26)00056-6. [Epub ahead of print]93 102707

Chemigenetic fluorescent biosensors in biological imaging - New trends and advances.

Dennis Pellanda, Elias Dressler, Michelle S Frei.

Chemigenetic fluorescent biosensors combine genetically encoded and synthetic approaches, showing superior photophysical properties compared with fluorescent protein-based tools and enabling subcellular and tissue specific targeting as well as selective analyte detection. Here, we review how two of the most widely used chemigenetic systems, HaloTag and fluorescence-activating and absorption-shifting tag (FAST), have been incorporated into biosensors and used to expand the functionality of biosensors. We highlight how bright, photostable, and far-red fluorophores improve in vivo and multiplexed imaging. We discuss how chemigenetic biosensors with fluorescence lifetime readouts are advancing quantitative imaging through fluorescence lifetime imaging microscopy (FLIM) and we showcase chemigenetic integrators that can record physiological events for post hoc analysis. Finally, we offer an outlook on where chemigenetic biosensors are headed and their anticipated impact on biological imaging in the coming years.

DOI: https://doi.org/10.1016/j.cbpa.2026.102707
Sci Rep. 2026 Jun 17. pii: 18698. [Epub ahead of print]16(1):

Messenger RNA-encoded reporters for monitoring cellular stress and bioenergetics.

Karen Kai-Lin Hwang, Qi Fang, Carine Nizard, Anne-Laure Bulteau, Knut Woltjen.

  The ability to monitor cellular processes in real-time is essential for understanding cell function, disease progression, and therapeutic responses. Engineered reporter proteins have been developed for monitoring cellular metabolism, stress responses, and bioenergetics. However, their use in primary cells is limited by inefficient plasmid transfection and the impracticality of generating and validating stable cell lines for each application. Here, we use in vitro transcription to generate mRNA-encoded metabolic trackers and achieve high transfection efficiencies in primary fibroblasts, cancer cells, and induced pluripotent stem cells. This approach provides a flexible platform for real-time monitoring of cellular processes in diverse cell types and overcomes the technical barriers of establishing stable cell lines by genetic modification. We confirm the activity of three ratiometric reporters that monitor pH, H2O2, and ATP levels in subcellular compartments. Our mRNA-based approach provides a versatile, efficient tool for real-time metabolic studies across basic and applied research, reducing reliance on commercially available reporters and broadening the applicability of metabolic reporters in patient-derived cell models.

Keywords:  ATP; Bioenergetics; Messenger RNA; Metabolic reporters; Reactive oxygen species; pH

DOI:  https://doi.org/10.1038/s41598-026-49851-y
Open Biol. 2026 Jun 17. pii: 250351. [Epub ahead of print]16(6):

Structural basis of Drosophila insulin receptor activation by DILP2 hormone.

Talha Shafi, Olga V Moroz, Huw T Jenkins, Maria Chechik, Michail N Iusupov, Marta Lubos, Jiří Jiráček, Pierre De Meyts, Andrzej Marek Brzozowski.

  Insulin-related hormones regulate key life processes in the animal kingdom, from metabolism to growth, lifespan and ageing, through an evolutionarily conserved insulin and insulin-like hormones signalling axis (IIS). In humans, the IIS axis is controlled by insulin, two insulin-like growth factors, two isoforms of the insulin receptor (hIR-A and -B), and its homologous IGF-1R. In Drosophila, this signalling engages seven insulin-like hormones (DILP1-7) and a single receptor (dmIR) that follows the blueprint of hIR/hIGF-1R. This report describes two cryo-EM structures of the dmIR ectodomain (dmIR-ECD) in complex with DILP2, revealing their relationship to other known DILP5/2/1 complexes. A high excess of DILP2 yielded two dmIR-ECD complexes in asymmetric conformations, similar to that observed in some complexes of hIR and in the dmIR-ECD:DILP5 complex. This stoichiometric and structural heterogeneity was not observed in DILP5:dmIR-ECD and DILP2 full-length dmIR assemblies. Also, in contrast to DILP5, the resistance of DILP2 to form more dmIR-ECD-saturated complexes, despite very high 40 : 1 excess of this hormone, suggests some structural bases for DILP1-7 specificities. This work expands understanding of the dmIR conformational flexibility, indicating that insect dmIR follows a more hIR:IGF-1R receptor hybrid mode of structural signal transduction pattern induced by various two-chains DILPs.

Keywords:   Drosophila melanogaster ; DILP; DILP2; DILP5; IGF-1; IGF-1R; insulin; insulin receptor; insulin signalling axis

DOI:  https://doi.org/10.1098/rsob.250351
Dent Mater J. 2026 Jun 13.

Spheroid construction using iPS cell-derived mesenchymal stem and endothelial cells.

Junyi Wang, Yufan Wu, Kengo Iwasaki, Yoshiya Hashimoto.

  Induced pluripotent stem cells (iPSCs) are a promising source for regenerative medicine due to their multilineage differentiation ability. We established a feeder-free xeno-reduced workflow to merge iPSC-derived mesenchymal stem cells (MSCs) and endothelial cells (ECs) into uniform hybrid spheroids for bone repair. iPSCs were differentiated into MSCs (CD73+/CD90+/CD105+; osteogenic, adipogenic, and chondrogenic) and ECs using a defined kit with brief fetal bovine serum exposure, yielding CD31+ cells that formed tube-like networks on the Matrigel. MSCs and ECs (5:1) were seeded in low-adhesion MicoCell® microwells, self-assembled within 4 h into hundreds of compact size-controlled spheroids, and maintained for 72 h under serum-free conditions. After clear unobstructed brain/body imaging cocktails and computational analysis (CUBIC) clearing and confocal immunofluorescence, CD90 and CD31 signals showed a distinct spatial organization within the three-dimensional structures, indicating the coexistence of both lineages. Notably, lumen formation was not observed at this stage. Overall, our feeder-free single-source system provides a reproducible platform for subsequent vascular maturation studies.

Keywords:  Co-culture; Spheroids; Tissue engineering; iPSC-derived MSCs and ECs

DOI:  https://doi.org/10.4012/dmj.2025-268
Cell Death Discov. 2026 Jun 17.

Fibroblast adipogenesis restricts hemangioma growth through a PPARγ/Hippo-YAP/TAZ axis that promotes endothelial apoptosis and cell cycle arrest.

Sheng-Ming Qu, Bing Wang.

Infantile hemangioma (HEM) is the most common benign vascular tumor in infancy and is characterized by a unique progression pattern involving rapid proliferation followed by spontaneous involution. Increasing evidence suggests that the tumor microenvironment plays a critical role in regulating endothelial cell behavior during HEM development. In this study, we investigated how fibroblast (FB) phenotypic remodeling influences hemangioma endothelial cell (HemEC) function. Through single-cell RNA sequencing analysis, we identified extensive communication between FBs and ECs within HEM tissues. Functional experiments revealed that adipogenically differentiated FBs markedly suppressed HemEC proliferation, migration, invasion, and tube formation while promoting apoptosis. Transcriptomic analysis further demonstrated that this inhibitory effect was mediated by activation of the Hippo-YAP/TAZ signaling pathway in ECs. Mechanistically, adipogenic differentiation significantly upregulated PPARG expression in FBs, which in turn triggered Hippo pathway activation in ECs, leading to YAP/TAZ phosphorylation and nuclear exclusion. Importantly, PPARG silencing in FBs or pharmacological inhibition of the Hippo pathway reversed these effects. Collectively, our findings reveal a previously unrecognized microenvironmental regulatory mechanism in which PPARγ-driven fibroblast adipogenesis suppresses HEM progression through activation of the Hippo-YAP/TAZ pathway in endothelial cells. This study provides new insights into stromal-endothelial communication in HEM and suggests that the PPARγ-Hippo signaling axis may represent a potential therapeutic target.Proposed molecular mechanism by which PPARγ-mediated FB adipogenic differentiation regulates Hippo-YAP/TAZ signaling activity in HemECs. Note: Created in Biorender.

DOI: https://doi.org/10.1038/s41420-026-03176-x
Autophagy. 2026 Jun 18. 1-3

Optineurin, an autophagy adaptor, stabilizes Rictor to maintain Akt/mTOR signaling and antigen presentation.

Rashmi Kadam, Deepak Shukla.

  Optineurin (OPTN) is widely recognized as a multifunctional selective autophagy receptor involved in cargo turnover. However, our recent findings uncover an unexpected function of OPTN that challenges the conventional view of autophagy adaptors. In dendritic cells (DCs), OPTN binds to and stabilizes Rictor, a key component of the mTORC2 complex. Loss of OPTN leads to depletion of Rictor, reduced Akt2 activity, and activation of the mTORC1/p70S6K1 pathway, culminating in enhanced phosphorylation of STAT3 at Ser727. Activated STAT3 transcriptionally induces the E3 ubiquitin ligase MARCH1, which promotes MHC II internalization, resulting in a striking inverse relationship between MARCH1 and MHC II expression in Optn-deficient cells. Together, these findings identify an unexpected signaling function of OPTN, independent of its canonical autophagy activities. By stabilizing Rictor and maintaining mTORC2-Akt2 signaling, OPTN links a classical autophagy adaptor to the regulation of antigen presentation and adaptive immunity. More broadly, our findings raise the possibility that selective autophagy receptors preserve cellular homeostasis not only through cargo clearance but also through context-dependent, non-degradative regulation of protein stability and signaling networks.Abbreviation: OPTN: Optineurin; mTORC1: mammalian target of rapamycin complex 1; mTORC2: mammalian target of rapamycin complex 1; Rictor: Rapamycin-Insensitive Companion of mTOR.

Keywords:  Antigen presentation; MHC II; mTOR signaling; optineurin; protein stabilization

DOI:  https://doi.org/10.1080/15548627.2026.2689040
Nat Commun. 2026 Jun 19.

Single-cell RNA sequencing profiles drug activity within spatially engineered 3D cultures.

Jessica J King, Alireza Mowla, Jessica A Kretzmann, Nishka Bhalla, Giselle Sugianto, Marck Norret, Ulrich D Kadolsky, Munir Iqbal, Alka Saxena, Sebastian E Amos, Yu Suk Choi, Brendan F Kennedy, K Swaminathan Iyer, Nicole M Smith, Cameron W Evans.

Spatial transcriptomic techniques provide a wealth of information useful in guiding drug development, while three-dimensional (3D) cell cultures have demonstrated power in accelerating drug approvals. However, techniques for robust spatial analysis of 3D cultures are limited. Here, we present a transfection-based method for constructing cellular spheroids through a layer-by-layer approach, in which DNA barcodes encode the spatial positioning of cells. Our technique facilitates multiplex single-cell RNA sequencing, providing spatial maps of gene expression and drug response, while correlative imaging reveals the locations of barcoded cell populations and quantifies local tissue elasticity. We show that model HeLa 3D spheroids display heterogeneous responses to drugs, which may arise through diffusion gradients of the drug, or from differences in metabolism, nutrient supply, and cellular stressors. The ability to create spatially encoded cellular assemblies may help to reveal spatial variation in gene expression within 3D culture models.

DOI: https://doi.org/10.1038/s41467-026-74587-8
Cell Rep. 2026 Jun 18. pii: S2211-1247(26)00654-6. [Epub ahead of print]45(7): 117576

VEGFR2 inhibition potentiates STING-mediated antitumor immunity.

Fangping Han, Pengbo Sun, Yuanyuan Wei, Jing Han, Yi Wang, Rui Kuai, Conggang Zhang.

  STING bridges innate and adaptive immunity to exert potent antitumor effects, and its agonists play emerging roles in combination therapies with tyrosine kinase inhibitors (TKIs). However, the interaction between STING and receptor tyrosine kinases (RTKs) remains incompletely understood. Here, we identify VEGFR2 as a negative regulator of cGAMP-STING signaling. Upon cGAMP stimulation, both STING and VEGFR2 are activated. Activated VEGFR2 recruits and activates AKT1 to attenuate STING activation. Conversely, STING suppresses VEGFR2 phosphorylation, establishing a reciprocal inhibitory feedback loop. A cell-based screen reveals that the VEGFR2 inhibitor Ki8751 not only relieves VEGFR2-AKT1-mediated suppression but also activates MyD88-dependent NF-κB signaling to further amplify STING responses. Additionally, we show that Ki8751 synergizes with cGAMP to elicit robust, STING-dependent antitumor immunity in vivo. Our findings identify the VEGFR2-STING regulatory axis and provide a mechanistic rationale for co-targeting VEGFR2 and STING to improve cancer immunotherapy.

Keywords:  CP: cancer; CP: immunology; NF-κB signaling; VEGFR2; antitumor immunity; cGAS-STING signaling pathway; cancer immunotherapy; innate immunity; type I IFN responses

DOI:  https://doi.org/10.1016/j.celrep.2026.117576