Protein tyrosine kinases (RTKs) modulate a wide range of pathophysiological events in several non-malignant disorders, including diabetic complications. To find new targets driving the development of diabetic cardiomyopathy (DCM), we profiled an RTKs phosphorylation array in diabetic mouse hearts and identified increased phosphorylated fibroblast growth factor receptor 1 (p-FGFR1) levels in cardiomyocytes, indicating that FGFR1 may contribute to the pathogenesis of DCM. Using primary cardiomyocytes and H9C2 cell lines, we discovered that high-concentration glucose (HG) transactivates FGFR1 kinase domain through toll-like receptor 4 (TLR4) and c-Src, independent of FGF ligands. Knocking down the levels of either TLR4 or c-Src prevents HG-activated FGFR1 in cardiomyocytes. RNA-sequencing analysis indicates that the elevated FGFR1 activity induces pro-inflammatory responses via MAPKs–NF κ B signaling pathway in HG-challenged cardiomyocytes, which further results in fibrosis and hypertrophy. We then generated cardiomyocyte-specific FGFR1 knockout mice and showed that a lack of FGFR1 in cardiomyocytes prevents diabetes-induced cardiac inflammation and preserves cardiac function in mice. Pharmacological inhibition of FGFR1 by a selective inhibitor, AZD4547, also prevents cardiac inflammation, fibrosis, and dysfunction in both type 1 and type 2 diabetic mice. These studies have identified FGFR1 as a new player in driving DCM and support further testing of FGFR1 inhibitors for possible cardioprotective benefits.
Tamoxifen (TAM) resistance has indicated a significant challenge during endocrine therapy for hormone-sensitive breast cancer. Thus, it is significant to elucidate the molecular events endowing TAM resistance to endocrine therapy. In this study, we found that epithelial-mesenchymal transition (EMT) was an important event to confer TAM resistance, and attenuating EMT by elevating connexin (Cx) 43 expression could reverse TAM resistance. Specifically, Cx43 overexpression improved TAM sensitivity, while Cx43 depletion facilitated TAM insensitivity by modulating EMT in T47D TAM-resistant and -sensitive cells, and transplanted xenografts. Importantly, we found a novel reciprocal regulation between Cx43 and c-Src/PI3K/Akt pathway contributing to EMT and TAM resistance in breast cancer. Moreover, we identified that Cx43 deficiency was significantly correlated with poor relapse-free survival in patients undergoing TAM treatment. Therefore, Cx43 represents a prognostic marker and an attractive target for breast cancer treatments. Therapeutic strategies designed to increase or maintain Cx43 function may be beneficial to overcome TAM resistance.
A novel protein tyrosine phosphatase 1B (PTP1B) inhibitor, FYGL, extracted from Ganoderma lucidum, was first reported to have an efficient hypoglycemic effect and high safety in vivo in our previous study. However, the underlying mechanism of the anti-diabetes activity was still unclear. The dominant effective component of FYGL was demonstrated to be a neutral hyperbranched proteoglycan macromolecule. Therefore, it is necessary to first elucidate how the biomacromolecule works at the cellular level, in order to understand its possible functional mechanism in vivo. Herein, we focused on demonstrating the cell internalization and endocytosis mechanism of FYGL in HepG2 cells. A series of cellular uptake pathways was explored, including clathrin-mediated endocytosis, caveolae/lipid-mediated endocytosis, and macropinocytosis. Confocal laser scanning microscopy and flow cytometry were used to demonstrate the absorption of FYGL by HepG2 cells. Furthermore, pharmacologically selective inhibitors and Western blot methods were used to demonstrate that macropinocytosis mediated by c-Src/PI3K cascades was the preferred route for the uptake of FYGL in cells. Our study provided the basis of uptake of FYGL for an efficient hypoglycemic effect. The functional mechanism of the signaling pathway in vivo will be reported in the future.
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