Biology subjects

Ryan, A. J.

Publications and source records attributed to Ryan, A. J..

5 recordsLinked to original sources

bioRxiv2023

Acid enhances salt taste by activating the epithelial sodium channel

Salt is often used to enhance the flavor of foods and drinks, and in turn, some foods and drinks may intensify the taste of salt. For example, highly acidic carbonated beverages sometimes accompany salty snacks, and margaritas made with acidic citrus are served in salt-rimmed glasses. However, whether and how acid might enhance salt taste remain unknown. Epithelial sodium channels (ENaC) in tongue taste cells detect dietary sodium. We found that acid irreversibly increased ENaC channel activity, with half-maximal activation occurring at pH 2.6. Acid altered ENaC gating by increasing the rate of channel opening and reducing the rate of channel closing. Acidic beverages Coca-Cola(R) and Pepsi(R) (pH 2.2-2.4) also stimulated ENaC current but Diet Coke(R) (pH 3.2) did not. In humans, we found that acid reduced the sodium taste detection threshold. These findings identify a functional interplay between dietary sodium and acid--by modulating ENaC gating, acid enhances salt taste.

physiology↗

bioRxiv2023

Radiation-induced persistent DNA damage response and late toxicity in cardiac tissue

BackgroundRadiotherapy treatment is a mainstay of cancer treatments including for thoracic malignancies such as lung or breast cancer. Cardiac toxicity is a recognised long-term complication of thoracic radiotherapy which persists despite improvements in therapeutic modalities. The mechanisms and potential therapeutic targets that could provide cardiac protection in the context of radiation therapy remain incompletely understood. Here we investigated early and late cardiac toxicity following irradiation using the A/J mouse model to identify potential molecular drivers. MethodsSingle doses of irradiation of either 13 or 15 Gy were delivered to female A/J mice aged 6 - 8 weeks using a SmART-PLAN system. ECG traces and analysis were performed on anaesthetised mice. Cardiac tissue was harvested up to 32 weeks following irradiation for histological analysis and second-harmonic imaging microscopy. ResultsCardiac RT resulted in cardiac conductivity abnormalities including prolonged QTc interval. Additionally, an increase in pericardial and perivascular fibrosis was noted with a marked increase in pericardial fibrosis at 15 Gy compared to 13 Gy. Persistent DNA damage response was identified in cardiomyocytes at 7 days post irradiation and polarisation of cardiac-infiltrating macrophages towards a CD206+ M2-like phenotype at the same timepoint. ConclusionsOur data introduce the A/J mouse as a novel model for the study of physiologically relevant early and late cardiac toxicities following irradiation. Early events that could contribute to long term toxicities include persistent DNA damage response and repolarisation of macrophages, further investigation of which could identify potential future cardioprotective therapeutic strategies.

cancer biology↗

bioRxiv2021

iRhom2 regulates ERBB signalling to promote KRAS-driven oncogenesis

Dysregulation of the ERBB/EGFR signalling pathway causes multiple types of cancer (1, 2). Accordingly, ADAM17, the primary shedding enzyme that releases and activates ERBB ligands, is tightly regulated. It has recently become clear that iRhoms, inactive members of the rhomboid-like superfamily, are regulatory cofactors for ADAM17 (3, 4). Here we show that oncogenic KRAS mutants target the cytoplasmic domain of iRhom2 to induce ADAM17-dependent shedding and the release of ERBB ligands. Activation of ERK1/2 by oncogenic KRAS induces the phosphorylation of iRhom2, recruitment of the phospho-binding 14-3-3 proteins, and consequent ADAM17-dependent shedding of ERBB ligands. In addition, cancer-associated mutations in iRhom2 act as sensitisers in this pathway by further increasing KRAS-induced shedding of ERBB ligands. This mechanism is conserved in lung cancer cells, where iRhom activity is required for tumour xenograft growth. In this context, the activity of oncogenic KRAS is modulated by the iRhom2-dependent release of ERBB ligands, thus placing iRhom2 as a central component of a positive feedback loop in lung cancer cells. Overall, the cytoplasmic domain of iRhom2 is a critical component of KRAS-induced oncogenesis of lung cancer cells. Both ADAM17 and iRhom2 have also been implicated in a wide range of other cancers (5-10), so the mechanism we have revealed may also have wider oncogenic significance.

cancer biology↗

bioRxiv2020

IGF targeting perturbs global replication through ribonucleotide reductase dysfunction

IGF receptor (IGF-1R) inhibition delays repair of radiation-induced DNA double-strand breaks (DSBs), prompting us to investigate whether IGF-1R influences endogenous DNA damage. We demonstrate that IGF-1R inhibition generates endogenous DNA lesions protected by 53BP1 bodies, indicating under-replicated DNA. We detect delayed replication fork progression in IGF-inhibited or IGF-1R depleted cancer cells, with activation of ATR-CHK1 signaling and the intra-S-phase checkpoint. This phenotype reflects unanticipated regulation of global replication by IGF-1, mediated via AKT, MEK/ERK and JUN to influence expression of ribonucleotide reductase (RNR) subunit RRM2. IGF-1R inhibition or depletion downregulate RRM2, compromising RNR function and dNTP supply. The resulting delay in fork progression and hallmarks of replication stress are rescued by RRM2 overexpression, confirming RRM2 as the critical factor through which IGF-1 regulates replication. Following targeted compound screens, we identify synergy between IGF inhibition and ATM loss, with evidence that IGF inhibition compromises growth of ATM null cells and xenografts. This synthetic lethal effect reflects conversion of single-stranded lesions in IGF-inhibited cells into toxic DSBs upon ATM inhibition. These data implicate IGF-1R in alleviating replication stress, and the identified reciprocal IGF:ATM co-dependence provides an approach to exploit this effect in ATM-deficient cancers.

cancer biology↗

bioRxiv2018

Hippo Pathway Deregulation Drives Tissue Stiffness and Cancer Stem-like Cells in Lung Adenocarcinoma

Lung cancer remains the leading cause of cancer-related death due to poor treatment responses arising from tumor heterogeneity and epigenetic aberrations. Here we show that adverse prognosis associated with epigenetically silenced tumour suppressor RASSF1A is a consequence of increased extracellular matrix, tumour stiffness and metastatic dissemination in vivo and in vitro. We find that lung cancer cells with methylated RASSF1A display constitutive nuclear YAP1 and expression of prolyl4hydroxylase2 (P4HA2) into extracellular matrix that correlates with increases collagen deposition. Furthermore, we identify an epigenetic axis in tumour cells where elevated ECM impedes the intrinsic suppression of WNT signaling (via TPBG/5T4) triggering b-catenin-YAP1 activation and thus results in a cancer stem-like programming. As key drivers, we identified RASSF1A and P4HA2 mediating the ECM-dependent stemness and metastatic dissemination in vivo. Re-expression of RASSF1A or inhibition of P4HA2 activity reverse these effects and increase levels of lung differentiation markers (TTF-1, Mucin5B) in vivo and in vitro. Our study identifies an epigenetic program to cancer stemness and metastatic progression of lung adenocarcinoma and P4HA2 as potential target for uncoupling ECM signals towards cancer stemness.

cancer biology↗