bims-raghud Biomed News
on RagGTPases in human diseases
Issue of 2025–12–21
five papers selected by
Irene Sambri, TIGEM



  1. bioRxiv. 2025 Nov 26. pii: 2025.11.24.690233. [Epub ahead of print]
      Cyclic adenosine monophosphate (cAMP) signaling is a major stimulus for lipid and glucose catabolism, yet catabolic processes like these can also coordinate with lysosome-dependent degradation. However, the impact of cAMP signaling on lysosomal dynamics remains unclear. Transcription factor EB (TFEB), a master regulator of lysosomal biogenesis, is regulated by stimulus-dependent nuclear-cytoplasmic shuttling through a variety of phosphorylation events. Here, we find that elevating intracellular cAMP with forskolin and IBMX induces rapid nuclear import of TFEB-GFP within 30 minutes and coincides with a transient upregulation of TFEB target lysosome genes. By 8 hours, TFEB returns to the cytoplasm, accompanied by transcriptional downregulation. Inhibition of cAMP-dependent protein kinase A (PKA) using H89 did not block nuclear import but unexpectedly caused sustained nuclear accumulation, indicating that PKA promotes TFEB nuclear export. Consistent with this, phosphoproteomic profiling revealed increased phosphorylation of a PKA-consensus motif (RRx S) during the export phase. These findings suggest that cAMP-PKA signaling plays a novel role in temporally "tuning" lysosomal gene expression by regulating TFEB nuclear-cytoplasmic shuttling.
    Summary: This study reveals that cAMP signaling dynamically regulates TFEB subcellular localization, promoting transient, calcium-dependent nuclear import as well as downstream, PKA-dependent export and phosphorylation at serines 466/467. These findings uncover a novel mechanism by which cAMP stimulation fine-tunes lysosomal gene expression by regulating TFEB nuclear import and export.
    DOI:  https://doi.org/10.1101/2025.11.24.690233
  2. Circulation. 2025 Dec 18.
       BACKGROUND: Doxorubicin (DOX), an effective chemotherapeutic drug for various cancers, has been demonstrated to induce cardiovascular toxicity in cancer survivors. Endothelial cell (EC) dysfunction is recognized to play a critical role in the onset and severity of cardiotoxicity associated with DOX. TFEB (transcription factor EB), a master regulator of autophagy and lysosome biogenesis, regulates cardiovascular homeostasis. In the present study, we aimed to test whether endothelial TFEB protects against EC damage and alleviates cardiac dysfunction induced by DOX treatment.
    METHODS: EC-specific TFEB transgenic mice, EC-specific TFEB knockout mice, and their corresponding littermate controls were administered DOX intravenously. Survival curves were generated, and cardiac functions were measured in mice. The effects of TFEB on mitochondrial reactive oxygen species production, autophagic flux, and apoptosis were evaluated in human and mouse cardiac microvascular ECs treated with DOX. RNA sequencing, single-cell RNA sequencing, and chromatin immunoprecipitation with quantitative polymerase chain reaction was performed to dissect molecular mechanisms in DOX-treated ECs in vitro and in vivo. Mice with endothelium-specific deficiency of DAB adaptor protein 2 (Dab2) were subjected to measurement of cardiac function and fibrosarcoma growth under DOX treatment.
    RESULTS: EC-specific TFEB transgenic mice showed significantly reduced mortality and improved cardiac function, together with attenuation of perivascular fibrosis after DOX treatment. By contrast, EC-specific TFEB knockout exacerbated DOX-induced cardiac dysfunction in mice. Furthermore, we observed that TFEB enhanced autophagy and reduced oxidative stress in cardiac microvascular ECs treated with DOX. In addition, TFEB preserved EC barrier integrity, alleviated proinflammatory cytokine release from cardiac microvascular ECs, and maintained the EC-cardiomyocyte communication, contributing to the protective effects of EC TFEB on cardiomyocyte function. Mechanistically, DAB2, a clathrin- and cargo-binding endocytic adaptor protein, was identified as a TFEB target gene in ECs. Accordingly, DAB2 knockdown attenuated the inhibitory effects of TFEB on apoptosis and the secretion of proinflammatory cytokines from cardiac microvascular ECs. In vivo, EC-specific Dab2 deficiency abolished the protective effect of EC TFEB on DOX-induced cardiac dysfunction.
    CONCLUSIONS: Taken together, endothelial TFEB protects against EC damage and cardiac dysfunction, constituting a potential target for treating cardiotoxicity induced by DOX. Our study provides new mechanistic insights into cardiotoxicity associated with chemotherapy.
    Keywords:  DAB2; cardiotoxicity; chemotherapy; endothelial toxicity; transcription factor EB
    DOI:  https://doi.org/10.1161/CIRCULATIONAHA.124.071774
  3. Stem Cell Res Ther. 2025 Dec 18.
       BACKGROUND: Kidney fibrosis is one of the pathological hallmarks of chronic kidney disease, likely contributing to the loss of kidney function. The mechanisms leading to kidney fibrosis and its reversibility is only partially understood, which hampers the development of therapeutic targets. Therefore, it is crucial to establish a robust human in vitro model that can be used to study kidney fibrosis and potential regeneration.
    METHODS: Human induced pluripotent stem cells (iPSC) were differentiated into kidney organoids. Fibrotic injury was induced by mimicking hypoxia (1% O2 48 h), inflammation (interleukin-1 beta (IL-1β) 96 h) or a combination (hypoxia and IL-1β). Organoids were harvested at injury onset and up to 2 weeks post-injury. Fibrosis was assessed by mRNA and protein expression of fibronectin (FN1) and collagen type I, regeneration was evaluated through the presence of CD133+ and CD24+ progenitor cells and markers for differentiated kidney cell types.
    RESULTS: The combination of hypoxia and IL-1β induced the strongest fibrotic response with significant upregulation of FN1 and collagen type I, and loss of tubular and glomerular markers. Over time, FN1 levels realigned with the control group, whereas collagen type I remained elevated. Tubular markers (Villin and ECAD) recovered to near-control levels, coinciding with increased CD133+ and CD24+ cell population and Ki67 expression. In contrast, PODXL+ glomerular structures showed limited recovery.
    CONCLUSIONS: We present a reproducible human kidney organoid model that captures both fibrotic remodeling and tubular regeneration following clinically relevant injury. This platform offers a valuable tool for studying kidney-specific fibrosis dynamics and testing anti-fibrotic or pro-regenerative strategies.
    Keywords:  Hypoxia; Inflammation; Ischemia reperfusion injury; Kidney fibrosis; Kidney organoid; Kidney regeneration
    DOI:  https://doi.org/10.1186/s13287-025-04866-6
  4. Cardiol Rev. 2025 Dec 15.
      Initially developed as antihyperglycemic agents, sodium-glucose cotransporter 2 (SGLT2) inhibitors have demonstrated therapeutic efficacy at every level of the cardiovascular disease spectrum. Multiple cardiovascular outcome trials have shown that SGLT2 inhibitors significantly reduce hospitalizations for heart failure as well as major adverse events. SGLT2 inhibitors have demonstrated remarkable advantages in lowering the risk of heart failure, even in individuals without diabetes, including those with heart failure. The exact mechanisms by which SGLT2 inhibitors provide cardiovascular protection are still unknown despite their widespread usage, indicating the need for more research. SGLT2 inhibitors have transformed the treatment of cardiovascular disease, providing substantial therapeutic promise for a wide range of patients. They are anticipated to become more and more important in the prevention and management of cardiovascular disease.
    Keywords:  diabetes mellitus; heart failure; sodium-glucose transporter 2 inhibitors
    DOI:  https://doi.org/10.1097/CRD.0000000000001154
  5. Sci Adv. 2025 Dec 19. 11(51): eaed8002
      When two genes linked to increased Parkinson's risk converge on a lysosome, LRRK2 mutation enhances lysosomal release of soluble GPNMB potentially contributing to synuclein pathology.
    DOI:  https://doi.org/10.1126/sciadv.aed8002