Decreased NMIIA heavy chain phosphorylation at S1943 promotes mitoxantrone resistance by upregulating BCRP and N-cadherin expression in breast cancer cells

Mitoxantrone (MX) is an effective treatment for breast cancer; however, high efflux of MX that is accomplished by breast cancer resistance protein (BCRP) leads to acquired multidrug resistance (MDR), reducing MX's therapeutic efficacy in breast cancer. Non-muscle myosin IIA (NMIIA) and its heavy phosphorylation at S1943 have been revealed to play key roles in tumor metastasis and progression, including in breast cancer; however, their molecular function in BCRP-mediated MDR in breast cancer remains unknown. In this study, we revealed that the expression of NMIIA heavy chain phosphorylation at S1943 was downregulated in BCRP-overexpressing breast cancer MCF-7/MX cells, and stable expression of NMIIA-S1943A mutant increased BCRP expression and promoted the resistance of MCF-7/MX cells to MX. Meanwhile, NMIIA S1943 phosphorylation induced by epidermal growth factor (EGF) was accompanied by the downregulation of BCRP in MCF-7/MX cells. Furthermore, stable expression of NMIIA-S1943A in MCF-7/MX cells resulted in upregulation of N-cadherin and the accumulation of β-catenin on the cell surface, which inhibited the nucleus translocation of β-catenin and Wnt/β-catenin-based proliferative signaling. EGF stimulation of MCF-7/MX cells showed the downregulation of N-cadherin and β-catenin. Our results suggest that decreased NMIIA heavy phosphorylation at S1943 increases BCRP expression and promotes MX resistance in breast cancer cells via upregulating N-cadherin expression.

Vitamin C supplementation attenuates oxidative stress and improves erythrocyte deformability in cardiac surgery with cardiopulmonary bypass

Cardiopulmonary bypass (CPB) depletes endogenous Vitamin C and generates oxidative stress in cardiac surgery. This study aimed to clarify whether Vitamin C supplementation reduces oxidant production and improves erythrocyte deformability in cardiac surgery with CPB. In a randomized and controlled design, 30 eligible patients undergoing cardiac surgery with hypothermic CPB were equally assigned to the Vitamin C group and control group. Subjects of the Vitamin C group and control group received an intravenous infusion of Vitamin C 20 mg·kg^-1 and a placebo during rewarming period of CPB, respectively. We measured the plasma level of reactive oxygen species (ROS) and phosphorylation levels of non-muscle myosin IIA (NMIIA) in erythrocyte membrane, as an index of erythrocyte deformability, before and after CPB. Vitamin C supplementation attenuated the surge in plasma ROS after CPB, mean 1.661 ± standard deviation 0.801 folds in the Vitamin C group and 2.743 ± 1.802 in the control group. The tyrosine phosphorylation level of NMIIA after CPB was upregulated in the Vitamin C group compared to the control group, 2.159 ± 0.887 folds and 1.384 ± 0.445 (P = 0.0237). In addition, the phosphorylation of vasodilator-stimulated phosphoprotein (VASP) and focal adhesion kinase (FAK) in erythrocytes was concurrently enhanced in the Vitamin C group after CPB. The phosphorylation level of endothelial nitric oxide synthase in erythrocytes was significantly increased in the Vitamin C group (1.734 ± 0.371 folds) compared to control group (1.102 ± 0.249; P = 0.0061). Patients receiving Vitamin C had lower intraoperative blood loss and higher systemic vascular resistance after CPB compared to controls. Vitamin C supplementation attenuates oxidative stress and improves erythrocyte deformability via VASP/FAK signaling pathway in erythrocytes during CPB.

MRIP Regulates the Myosin IIA Activity and DDR1 Function to Enable Collagen Tractional Remodeling

DDR1 is a collagen adhesion-mechanoreceptor expressed in fibrotic lesions. DDR1 mediates non-muscle myosin IIA (NMIIA)-dependent collagen remodeling. We discovered that the myosin phosphatase Rho-interacting protein (MRIP), is enriched in DDR1-NMIIA adhesions on collagen. MRIP regulates RhoA- and myosin phosphatase-dependent myosin activity. We hypothesized that MRIP regulates DDR1-NMIIA interactions to enable cell migration and collagen tractional remodeling. After deletion of MRIP in β1-integrin null cells expressing DDR1, in vitro wound closure, collagen realignment, and contraction were reduced. Cells expressing DDR1 and MRIP formed larger and more abundant DDR1 clusters on collagen than cells cultured on fibronectin or cells expressing DDR1 but null for MRIP or cells expressing a non-activating DDR1 mutant. Deletion of MRIP reduced DDR1 autophosphorylation and blocked myosin light chain-dependent contraction. Deletion of MRIP did not disrupt the association of DDR1 with NMIIA. We conclude that MRIP regulates NMIIA-dependent DDR1 cluster growth and activation. Accordingly, MRIP may provide a novel drug target for dysfunctional DDR1-related collagen tractional remodeling in fibrosis.

High-dose nitroglycerin administered during rewarming preserves erythrocyte deformability in cardiac surgery with cardiopulmonary bypass

OBJECTIVE

We aimed to determine whether high-dose nitroglycerin, a nitric oxide donor, preserves erythrocyte deformability during cardiopulmonary bypass and examines the signaling pathway of nitric oxide in erythrocytes.

METHODS

In a randomized and controlled fashion, forty-two patients undergoing cardiac surgery with hypothermic cardiopulmonary bypass were allocated to high-dose (N = 21) and low-dose groups (N = 21). During rewarming period, patients were given intravenous nitroglycerin with an infusion rate 5 and 1 µg·kg^-1 ·min^-1 in high-dose and low-dose groups, respectively. Tyrosine phosphorylation level of non-muscle myosin IIA in erythrocyte membrane was used as an index of erythrocyte deformability and analyzed using immunoblotting.

RESULTS

Tyrosine phosphorylation of non-muscle myosin IIA was significantly enhanced after bypass in high-dose group (3.729 ± 1.700 folds, P = .011) but not low-dose group (1.545 ± 0.595 folds, P = .076). Phosphorylation of aquaporin 1, vasodilator-stimulated phosphoprotein, and focal adhesion kinase in erythrocyte membrane was also upregulated in high-dose group after bypass. Besides, plasma nitric oxide level was highly correlated with fold change of non-muscle myosin IIA phosphorylation (Pearson's correlation coefficient .871).

CONCLUSIONS

High-dose nitroglycerin administered during cardiopulmonary bypass improves erythrocyte deformability through activating phosphorylation of aquaporin 1, vasodilator-stimulated phosphoprotein, and focal adhesion kinase in erythrocytes.

The tumor suppressor capability of p53 is dependent on non-muscle myosin IIA function in head and neck cancer

Over 300,000 patients develop squamous cell carcinoma of the head and neck (HNSCC) worldwide with 25-30% of patients ultimately dying from their disease. Currently, molecular biomarkers are not used in HNSCC but several genes have been identified including mutant TP53 (mutp53) Our recent work has identified an approach to stratify patients with tumors harboring high or low risk TP53 mutations. Non-muscle Myosin IIA (NMIIA) was recently identified as a tumor suppressor in HNSCC. We now demonstrate that low MYH9 expression is associated with decreased survival in patients with head and neck cancer harboring low-risk mutp53 but not high-risk mutp53. Furthermore, inhibition of NMIIA leads to increased invasion in cells harboring wildtype p53 (wtp53), which was not observed in high-risk mutp53 cells. This increased invasiveness of wtp53 following NMIIA inhibition was associated with reduced p53 target gene expression and was absent in cells expressing mutp53. This reduced expression may be due, in part, to a decrease in nuclear localization of wtp53. These findings suggest that the tumor suppressor capability of wtp53 is dependent upon functional NMIIA and that the invasive phenotype of high-risk mutp53 is independent of NMIIA.

DT-13 Ameliorates TNF-α-Induced Vascular Endothelial Hyperpermeability via Non-Muscle Myosin IIA and the Src/PI3K/Akt Signaling Pathway

DT-13(25(R,S)-ruscogenin-1-O-[β-d-glucopyranosyl-(1→2)][β-d-xylopyranosyl-(1→3)]-β-d-fucopyranoside) has been identified as an important factor in TNF-α-induced vascular inflammation. However, the effect of DT-13 on TNF-α-induced endothelial permeability and the potential molecular mechanisms remain unclear. Hence, this study was undertaken to elucidate the protective effect of DT-13 on TNF-α-induced endothelial permeability and the underlying mechanisms in vivo and in vitro. The in vivo results showed that DT-13 could ameliorate endothelial permeability in mustard oil-induced plasma leakage in the skin and modulate ZO-1 organization. In addition, the in vitro results showed that pretreatment with DT-13 could increase the transendothelial electrical resistance value and decrease the sodium fluorescein permeability coefficient. Moreover, DT-13 altered the mRNA and protein levels of ZO-1 as determined by real-time PCR, Western blotting, and immunofluorescence analyses. DT-13 treatment decreased the phosphorylations of Src, PI3K, and Akt in TNF-α-treated human umbilical vein endothelial cells (HUVECs). Further analyses with PP2 (10 µM, inhibitor of Src) indicated that DT-13 modulated endothelial permeability in TNF-α-induced HUVECs in an Src-dependent manner. LY294002 (10 µM, PI3K inhibitor) also had the same effect on DT-13 but did not affect phosphorylation of Src. Following decreased expression of non-muscle myosin IIA (NMIIA), the effect of DT-13 on the phosphorylations of Src, PI3K, and Akt was abolished. This study provides pharmacological evidence showing that DT-13 significantly ameliorated the TNF-α-induced vascular endothelial hyperpermeability through modulation of the Src/PI3K/Akt pathway and NMIIA, which play an important role in this process.

A non-enzymatic function of Golgi glycosyltransferases: mediation of Golgi fragmentation by interaction with non-muscle myosin IIA

The Golgi apparatus undergoes morphological changes under stress or malignant transformation, but the precise mechanisms are not known. We recently showed that non-muscle myosin IIA (NMIIA) binds to the cytoplasmic tail of Core 2 N-acetylglucosaminyltransferase mucus-type (C2GnT-M) and transports it to the endoplasmic reticulum for recycling. Here, we report that Golgi fragmentation induced by brefeldin A (BFA) or coatomer protein (β-COP) knockdown (KD) in Panc1-bC2GnT-M (c-Myc) cells is accompanied by the increased association of NMIIA with C2GnT-M and its degradation by proteasomes. Golgi fragmentation is prevented by inhibition or KD of NMIIA. Using multiple approaches, we have shown that the speed of BFA-induced Golgi fragmentation is positively correlated with the levels of this enzyme in the Golgi. The observation is reproduced in LNCaP cells which express high levels of two endogenous glycosyltransferases--C2GnT-L and β-galactoside α2,3 sialyltransferase 1. NMIIA is found to form complexes with these two enzymes but not Golgi matrix proteins. The KD of both enzymes or the prevention of Golgi glycosyltransferases from exiting endoplasmic reticulum reduced Golgi-associated NMIIA and decreased the BFA-induced fragmentation. Interestingly, the fragmented Golgi detected in colon cancer HT-29 cells can be restored to a compact morphology after inhibition or KD of NMIIA. The Golgi disorganization induced by the microtubule or actin destructive agent is NMIIA-independent and does not affect the levels of glycosyltransferases. We conclude that NMIIA interacts with Golgi residential but not matrix proteins, and this interaction is responsible for Golgi fragmentation induced by β-COP KD or BFA treatment. This is a novel non-enzymatic function of Golgi glycosyltransferases.