Sah, S. K. | bioRxiv Science

bioRxiv2026

Disturbed ATP and AMPK homeostasis in an AnkF377del mouse model for craniometaphyseal dysplasia

Craniometaphyseal dysplasia (CMD) is a rare genetic disorder characterized by hyperostosis of craniofacial bones and flared metaphyses of long bones. Mutations in ANKH (mouse orthologue ANK), a transmembrane protein mediating ATP and citrate efflux, cause the autosomal dominant form of CMD. How ANK mutations in CMD affect ATP/citrate homeostasis and downstream targets remains unknown. We determined that cellular ATP export, intracellular ATP levels, and plasma citric acid were significantly reduced in ANKF377del knock-in (AnkKI/KI) mice. Enrichment and pathway analyses of the plasma metabolome suggested the involvement of the citric acid cycle. It is known that AMPK is phosphorylated and activated when ATP is low. Phospho-AMPK was significantly upregulated in fusing AnkKI/KI osteoclasts, major contributors to CMD. AMPK inhibitor treatment only during the fusion stage of osteoclasts significantly restored dysfunctional AnkKI/KI osteoclasts, partly by modulating actin structures. Systemic administration of the AMPK inhibitor SBI-0206965 improved the positioning of cervical loops of incisors but failed to correct other skeletal abnormalities in AnkKI/KI mice. Limitations of systemic administration of SBI-0206965 include its off-target effects on other cell types and the inability to inhibit AMPK only on fusing osteoclasts. Nonetheless, this proof-of-principle study reveals an important role of the ATP-AMPK axis in CMD pathogenesis. Take-home messageSuppression of increased activation of AMPK restores the function of osteoclasts, suggesting that abnormal energy metabolism is an integral component of the disease phenotype in CMD.

molecular biology↗

bioRxiv2023

At least 10 genes on chromosome 5 of Candida albicans are downregulated in concert to control cell wall and to confer adaptation to caspofungin

Candida albicans is part of normal microbiota, however, can cause superficial and life threatening infection in immune-compromised individuals. Drugs from echinocandin (ECN) class that disrupt cell wall synthesis, are being used as a major treatment strategy against candidiasis. As the use of ECNs for the treatment of candidiasis is increasing, resistance against ECNs is also emerging. Previously, we reported involvement of 5 chromosome 2 (Ch2) genes in adaptation to ECN drugs. Here, we explored 22 candidate-genes on Ch5 that are consistently downregulated in independent mutants adapted to caspofungin (CAS), for their role in ECN adaptation. We also compared cell wall remodelling in CAS-adapted mutants and in 10 knockouts (KOs) from Ch5. Independent KO experiments as combined with broth microdilution assay, demonstrated that, as expected, 10 out of 22 Ch5 genes decrease ECN susceptibility by controlling the levels of three major components of the cell wall, glucan, mannan, and chitin. Some KOs decreased glucan or increased chitin or both. Similar cell wall remodelling, decreased glucan and increased chitin, was found in CAS-adapted mutants with no ploidy change. Some other KOs had no glucan change, but increased the level of either mannan or chitin. Our results identify the function of two uncharacterized genes, orf19.970 and orf19.4149.1, and expand the functions of DUS4, RPS25B, UAP1, URA7, RPO26, HAS1, and CKS1. The function of CHT2, as negative regulator of ECN susceptibility, has been previously established. Importantly, half of the above genes are essential indicating that essential processes are involved in cell wall remodelling for adaptation to ECNs. Also important, orf19.970 and orf19.4149.1 have no human orthologues. Finally, our work shows that multiple mechanisms are used by C. albicans cells to remodel cell wall in order to adapt to CAS. This work continues to identify common pathways that are involved in drug adaptation, as well as new genes controlling ECN susceptibility and reveals new targets for development of novel antifungal drugs.

genetics↗