Dataset Information

Mechanoactivation of NOX2-generated ROS elicits persistent TRPM8 Ca2+ signals that are inhibited by oncogenic KRas.

ABSTRACT: Changes in the mechanical microenvironment and mechanical signals are observed during tumor progression, malignant transformation, and metastasis. In this context, understanding the molecular details of mechanotransduction signaling may provide unique therapeutic targets. Here, we report that normal breast epithelial cells are mechanically sensitive, responding to transient mechanical stimuli through a two-part calcium signaling mechanism. We observed an immediate, robust rise in intracellular calcium (within seconds) followed by a persistent extracellular calcium influx (up to 30 min). This persistent calcium was sustained via microtubule-dependent mechanoactivation of NADPH oxidase 2 (NOX2)-generated reactive oxygen species (ROS), which acted on transient receptor potential cation channel subfamily M member 8 (TRPM8) channels to prolong calcium signaling. In contrast, the introduction of a constitutively active oncogenic KRas mutation inhibited the magnitude of initial calcium signaling and severely blunted persistent calcium influx. The identification that oncogenic KRas suppresses mechanically-induced calcium at the level of ROS provides a mechanism for how KRas could alter cell responses to tumor microenvironment mechanics and may reveal chemotherapeutic targets for cancer. Moreover, we find that expression changes in both NOX2 and TRPM8 mRNA predict poor clinical outcome in estrogen receptor (ER)-negative breast cancer patients, a population with limited available treatment options. The clinical and mechanistic data demonstrating disruption of this mechanically-activated calcium pathway in breast cancer patients and by KRas activation reveal signaling alterations that could influence cancer cell responses to the tumor mechanical microenvironment and impact patient survival.

SUBMITTER: Pratt SJP

PROVIDER: S-EPMC7584994 | biostudies-literature | 2020 Oct

REPOSITORIES: biostudies-literature

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Mechanoactivation of NOX2-generated ROS elicits persistent TRPM8 Ca<sup>2+</sup> signals that are inhibited by oncogenic KRas.

Pratt Stephen J P SJP Lee Rachel M RM Chang Katarina T KT Hernández-Ochoa Erick O EO Annis David A DA Ory Eleanor C EC Thompson Keyata N KN Bailey Patrick C PC Mathias Trevor J TJ Ju Julia A JA Vitolo Michele I MI Schneider Martin F MF Stains Joseph P JP Ward Christopher W CW Martin Stuart S SS

Proceedings of the National Academy of Sciences of the United States of America 20201005 42

Changes in the mechanical microenvironment and mechanical signals are observed during tumor progression, malignant transformation, and metastasis. In this context, understanding the molecular details of mechanotransduction signaling may provide unique therapeutic targets. Here, we report that normal breast epithelial cells are mechanically sensitive, responding to transient mechanical stimuli through a two-part calcium signaling mechanism. We observed an immediate, robust rise in intracellular c ...[more]

PMID: 33020304

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Project description:Excessive mitochondrial reactive oxygen species (ROS) emission is a critical component in the etiology of ischemic injury. Complex I and complex III of the electron transport chain are considered the primary sources of ROS emission during cardiac ischemia and reperfusion (IR) injury. Several factors modulate ischemic ROS emission, such as an increase in extra-matrix Ca(2+), a decrease in extra-matrix pH, and a change in substrate utilization. Here we examined the combined effects of these factors on ROS emission from respiratory complexes I and III under conditions of simulated IR injury. Guinea pig heart mitochondria were suspended in experimental buffer at a given pH and incubated with or without CaCl2. Mitochondria were then treated with either pyruvate, a complex I substrate, followed by rotenone, a complex I inhibitor, or succinate, a complex II substrate, followed by antimycin A, a complex III inhibitor. H2O2 release rate and matrix volume were compared with and without adding CaCl2 and at pH 7.15, 6.9, or 6.5 with pyruvate + rotenone or succinate + antimycin A to simulate conditions that may occur during in vivo cardiac IR injury. We found a large increase in H2O2 release with high [CaCl2] and pyruvate + rotenone at pH 6.9, but not at pHs 7.15 or 6.5. Large increases in H2O2 release rate also occurred at each pH with high [CaCl2] and succinate + antimycin A, with the highest levels observed at pH 7.15. The increases in H2O2 release were associated with significant mitochondrial swelling, and both H2O2 release and swelling were abolished by cyclosporine A, a desensitizer of the mitochondrial permeability transition pore (mPTP). These results indicate that ROS production by complex I and by complex III is differently affected by buffer pH and Ca(2+) loading with mPTP opening. The study suggests that changes in the levels of cytosolic Ca(2+) and pH during IR alter the relative amounts of ROS produced at mitochondrial respiratory complex I and complex III.

Project description:Reactive oxygen species (ROS) produced by the inducible NADPH oxidase type 2 (NOX2) complex are essential for clearing certain infectious organisms but may also have a role in regulating inflammation and immune response. For example, ROS is involved in myeloid derived suppressor cell (MDSC)- and regulatory T cell (T(reg)) mediated T- and NK-cell suppression. However, abundant ROS produced within the tumor microenvironment, or by the tumor itself may also yield oxidative stress, which can blunt anti-tumor immune responses as well as eventually leading to tumor toxicity. In this study we aimed to decipher the role of NOX2-derived ROS in a chemically (by methylcholanthrene (MCA)) induced sarcoma model. Superoxide production by NOX2 requires the p47(phox) (NCF1) subunit to organize the formation of the NOX2 complex on the cell membrane. Homozygous mutant mice (NCF1*/*) have a functional loss of their super oxide burst while heterozygous mice (NCF1*/+) retain this key function. Mice harboring either a homo- or a heterozygous mutation were injected intramuscularly with MCA to induce sarcoma formation. We found that NOX2 functionality does not determine tumor incidence in the tested MCA model. Comprehensive immune monitoring in tumor bearing mice showed that infiltrating immune cells experienced an increase in their oxidative state regardless of the NOX2 functionality. While MCA-induced sarcomas where characterized by a T(reg) and MDSC accumulation, no significant differences could be found between NCF1*/* and NCF1*/+ mice. Furthermore, infiltrating T cells showed an increase in effector-memory cell phenotype markers in both NCF1*/* and NCF1*/+ mice. Tumors established from both NCF1*/* and NCF1*/+ mice were tested for their in vitro proliferative capacity as well as their resistance to cisplatin and radiation therapy, with no differences being recorded. Overall our findings indicate that NOX2 activity does not play a key role in tumor development or immune cell infiltration in the chemically induced MCA sarcoma model.

Dataset Information

Mechanoactivation of NOX2-generated ROS elicits persistent TRPM8 Ca2+ signals that are inhibited by oncogenic KRas.

Publications

Mechanoactivation of NOX2-generated ROS elicits persistent TRPM8 Ca<sup>2+</sup> signals that are inhibited by oncogenic KRas.

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