Transient receptor potential vanilloid type 4 (TRPV4) is a calcium-permeable nonselective cation channel, originally described in 2000 by research teams led by Schultz (Nat Cell Biol 2: 695–702, 20...

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TRPV4: Molecular conductor of a diverse orchestra

TRPC channels: Structure, function, regulation and recent advances in small molecular probes.

Background
Chemotherapy resistance has become a serious challenge in the treatment of breast cancer. Previous studies showed cells can transfer proteins, including those responsible for drug resistance to adjacent cells via exosomes.

Methods
The switches of drug resistance via exosomes transfer were assessed by CellTiter-Blue Viability assay, flow cytometry, and immunostaining analysis. Relative protein levels of Ubiquitin carboxyl terminal hydrolase-L1 (UCH-L1), P-glycoprotein (P-gp), extracellular-signal regulated protein kinase1/2 (ERK1/2), and phospho-extracellular-signal regulated protein kinase1/2 (p-ERK1/2) were measured by Western blot. Immunohistochemistry was performed on 93 breast cancer samples to assess the associations of UCH-L1 levels with immunofluorescence value of UCH-L1 in circulating exosomes.

Result
The Adriamycin-resistant human breast cancer cells (MCF7/ADM) secreted exosomes carrying UCH-L1 and P-gp proteins into the extracellular microenvironment then integrated into Adriamycin-sensitive human breast cancer cells (MCF7/WT) in a time-dependent manner, transferring the chemoresistance phenotype. Notably, in blood samples from patients with breast cancer, the level of exosomes carrying UCH-L1 before chemotherapy was significantly negatively correlated with prognosis.

Conclusion
Our study demonstrated that UCH-L1-containing exosomes can transfer chemoresistance to recipient cells and these exosomes may be useful as non-invasive diagnostic biomarkers for detection of chemoresitance in breast cancer patients, achieving more effective and individualized chemotherapy.

UCH-L1-containing exosomes mediate chemotherapeutic resistance transfer in breast cancer.

Adriamycin is a first-line chemotherapy agent against cancer, but the development of resistance has become a major problem. Although autophagy is considered to be an adaptive survival response in response to chemotherapy and may be associated with chemoresistance, its inducer and the underlying molecular mechanisms remain unclear. Here, we demonstrate that adriamycin up-regulates the both levels of TRPC5 and autophagy, and the increase in autophagy is mediated by TRPC5 in breast cancer cells. Blockade of TRPC5 or autophagy increased the sensitivity to chemotherapy in vitro and in vivo. Notably, we revealed a positive correlation between TRPC5 and the autophagy-associated protein LC3 in paired patients with or without anthracycline-taxane-based chemotherapy. Furthermore, pharmacological inhibition and gene-silencing showed that the cytoprotective autophagy mediated by TRPC5 during adriamycin treatment is dependent on the CaMKKβ/AMPKα/mTOR pathway. Moreover, adriamycin-resistant MCF-7/ADM cells maintained a high basal level of autophagy, and silencing of TRPC5 and inhibition of autophagy counteracted the resistance to adriamycin. Thus, our results revealed a novel role of TRPC5 as an inducer of autophagy, and this suggests a novel mechanism of drug resistance in chemotherapy for breast cancer.

TRPC5-induced autophagy promotes drug resistance in breast carcinoma via CaMKKβ/AMPKα/mTOR pathway.

Modulation of TRPV4 by diverse mechanisms.

Aims Vascular endothelial cells synthesize and release vasodilators such as nitric oxide (NO) and epoxyeicosatrienoic acids (EETs). NO is known to inhibit EET-induced smooth muscle hyperpolarization and relaxation. This study investigates the underlying mechanism of this inhibition.

Methods and results Through measurements of membrane potential and arterial tension, we show that 11,12-EET induced membrane hyperpolarization and vascular relaxation in endothelium-denuded porcine coronary arteries. These responses were suppressed by S -nitroso- N -acetylpenicillamine (SNAP) and 8-Br-cGMP, an NO donor and a membrane-permeant analogue of cGMP, respectively. The inhibitory actions of SNAP and 8-Br-cGMP on 11,12-EET-induced membrane hyperpolarization and vascular relaxation were reversed by hydroxocobalamin, an NO scavenger; ODQ, a guanylyl cyclase inhibitor; and KT5823, a protein kinase G (PKG) inhibitor. The inhibitory actions of SNAP and 8-bromo cyclic GMP (8-Br-cGMP) on the EET responses were also abrogated by shielding TRPC1-PKG phosphorylation sites with an excessive supply of exogenous PKG substrates, TAT-TRPC1S172 and TAT-TRPC1T313. Furthermore, a phosphorylation assay demonstrated that PKG could directly phosphorylate TRPC1 at Ser172 and Thr313. In addition, 11,12-EET failed to induce membrane hyperpolarization and vascular relaxation when TRPV4, TRPC1, or KCa1.1 was selectively inhibited. Co-immunoprecipitation studies demonstrated that TRPV4, TRPC1, and KCa1.1 physically associated with each other in smooth muscle cells.

Conclusion Our findings demonstrate a novel role of the NO-cGMP-PKG pathway in the inhibition of 11,12-EET-induced smooth muscle hyperpolarization and relaxation via PKG-mediated phosphorylation of TRPC1.

https://ihome.sbs.cuhk.edu.hk/YAOXiaoQiang/ourresearch/reference/journal/138.full.pdf

Yan Wang

Papers

Nitric oxide and protein kinase G act on TRPC1 to inhibit 11,12-EET-induced vascular relaxation

Chemotherapy enhances tumor vascularization via Notch signaling-mediated formation of tumor-derived endothelium in breast cancer.