Biology subjects

Azoulay, S.

Publications and source records attributed to Azoulay, S..

3 recordsLinked to original sources

bioRxiv2026

Structural and cellular insights into the inhibition of the drug efflux activity of the HEDGEHOG receptor PATCHED1

PTCH1, the receptor for the Sonic Hedgehog morphogen, mediates cholesterol transport across the plasma membrane by harnessing the proton motive force. In cancer, PTCH1 is frequently overexpressed and promotes chemoresistance by transporting drugs such as doxorubicin (dxr) out of cells. Among the inhibitors identified, PAH stands out for its ability to significantly enhance the efficacy of several chemotherapeutic drugs on melanoma and breast cancer cells. To investigate PTCH1s structure in complex with its inhibitor PAH, we overexpressed a construct spanning residues 1-619 and 720-1305 in HEK293 cells. The protein localized to the membrane, and transfected cells exhibited reduced sensitivity to dxr compared to control cells. Additionally, we observed a pH-dependent efflux of dxr, which was reversed by PAH, confirming that the PTCH1 construct used in this study functions as an active drug-efflux pump. In the structure of PTCH1 bound to PAH determined using cryo-electron microscopy, PAH occupies a hydrophobic cavity in an extracellular domain which is normally occupied by cholesterol in other PTCH1 structures, and engages in a key hydrogen bond via one of its hydroxyl groups, a feature previously established as essential for its inhibitory function. These findings not only clarify the molecular basis of PAHs action but also provide a structural roadmap for rational drug design, enabling the development of next-generation inhibitors with enhanced potency.

biochemistry↗

bioRxiv2026

A Calcium-mediated signaling pathway modulates ion homeostasis via HKT1;1 during Arabidopsis seed germination under salt stress

Soil salinization severely constrains seedling establishment by disrupting cellular Na/K homeostasis. Calcium (Ca{superscript 2}) signaling contributes to the re-establishment of ion balance during early growth, yet the mechanisms linking Ca{superscript 2} perception to ion transport regulation remain unclear. Here, we identify a Ca{superscript 2}-responsive regulatory module in Arabidopsis thaliana comprising CALMODULIN-BINDING TRANSCRIPTION ACTIVATOR 6 (CAMTA6), the TYPE 2C PROTEIN PHOSPHATASE PP2C49, and the HIGH-AFFINITY K TRANSPORTER HKT1;1, and define their coordinated roles during germination under salt stress. Spatial promoter analyses revealed that NaCl induces CAMTA6 expression at cotyledon margins, while CaCl2 stimulates HKT1;1 transcription in the radicle, consistent with CAMTA6-mediated repression of HKT1;1. In camta6 mutants, PP2C49 expression expanded beyond its normal radicle-restricted domain, indicating CAMTA6-dependent spatial control. Promoter activation assays in planta demonstrated CAMTA6-dependent transactivation of the HKT1;1 and PP2C49 promoters. Treatment with the PP2C inhibitor sanguinarine enhanced germination under salinity in the wild type, but not in hkt1 nor in the salt-tolerant camta6 and pp2c49 mutants. Sanguinarine restricted CAMTA6 promoter activity to cotyledon margins, suppressed PP2C49 expression, and enhanced HKT1;1 accumulation in the radicle, collectively supporting improved Na/K balance. Transcriptome profiling further revealed additional Ca{superscript 2}-responsive PP2C genes under CAMTA6-dependent regulation. Together, these findings establish a Ca{superscript 2}-regulated transcriptional network coordinating ion homeostasis during germination and suggest strategies to support seedling performance in saline environments. Significance statementSalinity impairs germination largely by disrupting Na/K homeostasis, yet the signaling pathways that protect seedlings at this stage remain poorly defined. We identify a calcium-responsive regulatory mechanism that spatially coordinates transcriptional control of genes involved in ion transport during early development, providing a mechanistic basis for improving seedling establishment in saline soils.

plant biology↗

bioRxiv2025

Inhibition of PTCH1 drug efflux activity enhances chemotherapy efficacy against triple negative breast cancer

Triple-negative breast cancer (TNBC) is the most aggressive breast cancer subgroup characterized by a high risk of resistance to chemotherapies and high relapse potential. High levels of mRNA from the Hedgehog receptor PTCH1 are associated with poor prognosis in TNBC. PTCH1 is overexpressed in many aggressive cancers. We previously reported that PTCH1 is a multidrug transporter that triggers resistance to chemotherapy of adrenocortical carcinoma and melanoma cells, and that inhibiting PTCH1 drug efflux strongly enhanced chemotherapy efficacy on these cell lines both in vitro and in vivo. In the present study, we found that PTCH1 inhibition also significantly inhibited doxorubicin efflux in three TNBC cell lines leading to a strong increase of the cytotoxic effect of doxorubicin and docetaxel, and an inhibition of cell migration. Altogether, our data highlight the therapeutic potential of targeting PTCH1 drug efflux activity using drug association strategies for the treatment of TNBC patients.

cancer biology↗