Signaling events leading to fungal growth and septation depend on key cytoskeletal proteins, including actin, microtubules, and septin GTPases, that assemble into oligomeric structures and filaments and associate with cellular membranes. We previously demonstrated that deleting calcineurin, a calmodulin-dependent protein phosphatase in Aspergillus fumigatus, results in stunted hyphal growth, hyperbranching, and aberrant septation. Supporting this, we found that calcineurin colocalizes with actin during early septation, and its localization and activity at mature septa are essential for regular septation, hyphal extension, and growth. However, calcineurin's interactions and functions at the septa remain unknown. In this study, using GFP-Trap® chromatography and mass spectrometry, we show that calcineurin interacts with actin, tubulin, and septins. To better understand the significance of calcineurin-septin interactions for hyphal extension and septation, we used fluorescence microscopy to visualize septins (AspA∼E) in the A. fumigatus calcineurin double deletion mutant (ΔcnaA ΔcnaB). Strikingly, all septins exhibited aberrant localization patterns in the calcineurin mutant. Specifically, AspA mislocalized from punctate structures in the cytoplasm, AspB localized to longer rod-like structures, AspC mislocalized from the septa, AspD mislocalized from tubular and ring-like structures, and AspE mislocalized from long filaments to punctate structures resembling microtubule-organizing centers (MTOCs). Treatment with the calcineurin-specific inhibitor FK506 also caused AspE to mislocalize from filaments to MTOCs, a pattern mimicking the treatment with microtubule inhibitor nocodazole. These results highlight the unique importance of calcineurin for complete septin organization, which is crucial for proper septation and ultimately hyphal growth.
This study investigates the potential bidirectional communication between non-skeletal organs and bone in disease states such as liver fibrosis and atherosclerosis. Transcriptomic analysis of mouse models of liver fibrosis and atherosclerosis identified 782 and 878 differentially expressed potential secreted factors, respectively. Mendelian randomization analysis revealed causal associations between multiple secreted factors (e.g., Sfrp1, Il18bp, Adam11) and bone mineral density, with shared bone-influencing factors across both disease models. Integration with population-based proteome-phenome databases further indicated that these factors predominantly correlate with osteoporosis risk, primarily as risk factors. Concurrently, proteomic analysis of bone tissue from disease model mice revealed that liver fibrosis significantly impacts pathways related to bone development and cartilage formation, while atherosclerosis primarily disrupts bone remodeling and resorption processes. Furthermore, simultaneous detection of proteins in bone tissue and bone marrow supernatant revealed significant alterations in osteokines (e.g., CD5L, SERPING1) in disease conditions, which suggested genetic or epidemiological associations with multiple systemic diseases. Collectively, by integrating multi-omics data from murine models and human populations, this study screens candidate proteins for liver-bone and artery-bone crosstalk, suggesting that the liver and arteries may remotely regulate bone metabolism via secreted factors in pathological states, and that bone may influence systemic processes through endocrine feedback, thereby laying a theoretical foundation for future functional validation of these bidirectional regulatory mechanisms.
