Fibroblast growth factor homologous factors are potential ion channel modifiers associated with cardiac arrhythmias

Increased expression of FGF14 and SCN2A/SCN11A is associated with better survival of HCC patients

BACKGROUND

The clinical significance of fibroblast growth factor receptors (FGFRs) and their ligands in hepatocellular carcinoma (HCC) is extensively studied. Recently, regulation of voltage-gated sodium channels by FGFs in cancer has been reported.

MATERIALS AND METHODS

We investigated the relationship between FGF family genes and voltage-gated sodium channel genes (SCN) using three independent microarray and RNA-seq cohorts HCC patients. In vitro validation of 100 tissues of HCC patients with 50 control samples was performed. Statistical validation included the Wilcoxon test, Mann-Whitney U-test, correlation, Kaplan-Meier survival, and univariate and multivariate Cox regression survival analyses.

RESULT

The initial analysis of intracrine FGF (iFGF) ligands showed dysregulation of iFGF genes in HCC with strong association with each other in all datasets. According to in vitro analysis, overexpression of FGF14 was also observed in HCC patients suggesting potential role of FGF14 in HCC.Furthermore, network analysis showed that FGF14 was strongly interacting with SCN genes. Interestingly, SCN genes were also found in HCC samples with a positive correlation with FGF14 expression. The clinical analysis showed that FGF14, SCN2A and SCN11A are significantly associated with better disease-free survival, whereas multivariate regression analysis showed SCN11A as an independent predictor of disease-free survival in HCC patients.

CONCLUSION

The dysregulation of FGF14 and SCN family genes suggests a new molecular mechanism in the regulation of HCC. Furthermore, SCN11A was identified as a possible predictor for disease-free survival in HCC. Investigating these gene families using clinical studies may lead to new therapeutic approaches for HCC treatment.

Inducible Fgf13 ablation alleviates cardiac fibrosis via regulation of microtubule stability

Fibroblast growth factor (FGF) isoform 13, a distinct type of FGF, boasts significant potential for therapeutic intervention in cardiovascular dysfunctions. However, its impact on regulating fibrosis remains unexplored. This study aims to elucidate the role and mechanism of FGF13 on cardiac fibrosis. Here, we show that following transverse aortic constriction (TAC) surgery, interstitial fibrosis and collagen content increase in mice, along with reduced ejection fraction and fractional shortening, augmented heart mass. However, following Fgf13 deletion, interstitial fibrosis is decreased, ejection fraction and fractional shortening are increased, and heart mass is decreased, compared with those in the TAC group. Mechanistically, incubation of cardiac fibroblasts with transforming growth factor β (TGFβ) increases the expressions of types I and III collagen proteins, as well as α-smooth muscle actin (α-SMA) proteins, and enhances fibroblast proliferation and migration. In the absence of Fgf13, the expressions of these proteins are decreased, and fibroblast proliferation and migration are suppressed, compared with those in the TGFβ-stimulated group. Overexpression of FGF13, but not FGF13 mutants defective in microtubule binding and stabilization, rescues the decrease in collagen and α-SMA protein and weakens the proliferation and migration function of the Fgf13 knockdown group. Furthermore, Fgf13 knockdown decreases ROCK protein expression via microtubule disruption. Collectively, cardiac Fgf13 knockdown protects the heart from fibrosis in response to haemodynamic stress by modulating microtubule stabilization and ROCK signaling pathway.

The intracellular interplay between galectin-1 and FGF12 in the assembly of ribosome biogenesis complex

Galectins constitute a class of lectins that specifically interact with β-galactoside sugars in glycoconjugates and are implicated in diverse cellular processes, including transport, autophagy or signaling. Since most of the activity of galectins depends on their ability to bind sugar chains, galectins exert their functions mainly in the extracellular space or at the cell surface, which are microenvironments highly enriched in glycoconjugates. Galectins are also abundant inside cells, but their specific intracellular functions are largely unknown. Here we report that galectin-1, -3, -7 and -8 directly interact with the proteinaceous core of fibroblast growth factor 12 (FGF12) in the cytosol and in nucleus. We demonstrate that binding of galectin-1 to FGF12 in the cytosol blocks FGF12 secretion. Furthermore, we show that intracellular galectin-1 affects the assembly of FGF12-containing nuclear/nucleolar ribosome biogenesis complexes consisting of NOLC1 and TCOF1. Our data provide a new link between galectins and FGF proteins, revealing an unexpected glycosylation-independent intracellular interplay between these groups of proteins.

FGF13A interacts with NPM1 and UBF and inhibits the invasion of bladder cancer cells

Bladder cancer (BC) invasion is a critical factor that impacts the prognosis and quality of life of patients. However, the underlying mechanisms of BC invasion is far from clear. Fibroblast growth factor 13 (FGF13), a non-secretory FGF, has been found to be ectopically expressed in various tumors and implicated in tumor development, but its potential association to BC has not been investigated. Here, we reported that the expression of FGF13A, one nucleolar isoform of FGF13, was downregulated in BC patients and negatively associated with tumor invasion. Additionally, we demonstrated that overexpression of FGF13A could inhibit the migration and invasion of BC 5637 and T24 cells. We also confirmed the localization of FGF13A in the nucleolus and its interaction with nucleoproteins NPM1 and UBP. Subsequently, we identified that the N-terminal region of FGF13A was essential for its nucleolus location and interaction with NPM1. Furthermore, we found that FGF13A inhibited the generation of nascent ribosomal RNA and suppressed the migration and invasion of BC cells through its N-terminal region. Our research establishes, for the first time, a correlation between the expression of FGF13A and the onset and progression of BC. This provides novel insights into the role of FGF13A in the development of BC.

N-glycosylation acts as a switch for FGFR1 trafficking between the plasma membrane and nuclear envelope

Fibroblast growth factor receptor 1 (FGFR1) is a heavily N-glycosylated cell surface receptor tyrosine kinase that transmits signals across the plasma membrane, in response to fibroblast growth factors (FGFs). Balanced FGF/FGFR1 signaling is crucial for the development and homeostasis of the human body, and aberrant FGFR1 is frequently observed in various cancers. In addition to its predominant localization to the plasma membrane, FGFR1 has also been detected inside cells, mainly in the nuclear lumen, where it modulates gene expression. However, the exact mechanism of FGFR1 nuclear transport is still unknown. In this study, we generated a glycosylation-free mutant of FGFR1, FGFR1.GF, and demonstrated that it is localized primarily to the nuclear envelope. We show that reintroducing N-glycans into the D3 domain cannot redirect FGFR1 to the plasma membrane or exclude the receptor from the nuclear envelope. Reestablishment of D2 domain N-glycans largely inhibits FGFR1 accumulation in the nuclear envelope, but the receptor continues to accumulate inside the cell, mainly in the ER. Only the simultaneous presence of N-glycans of the D2 and D3 domains of FGFR1 promotes efficient transport of FGFR1 to the plasma membrane. We demonstrate that while disturbed FGFR1 folding results in partial FGFR1 accumulation in the ER, impaired FGFR1 secretion drives FGFR1 trafficking to the nuclear envelope. Intracellular FGFR1.GF displays a high level of autoactivation, suggesting the presence of nuclear FGFR1 signaling, which is independent of FGF. Using mass spectrometry and proximity ligation assay, we identified novel binding partners of the nuclear envelope-localized FGFR1, providing insights into its cellular functions. Collectively, our data define N-glycosylation of FGFR1 as an important regulator of FGFR1 kinase activity and, most importantly, as a switchable signal for FGFR1 trafficking between the nuclear envelope and plasma membrane, which, due to spatial restrictions, shapes FGFR1 interactome and cellular function. Video Abstract.

Fibroblast growth factor receptor signalling dysregulation and targeting in breast cancer

Fibroblast Growth Factor Receptor (FGFR) signalling plays a critical role in breast embryonal development, tissue homeostasis, tumorigenesis and metastasis. FGFR, its numerous FGF ligands and signalling partners are often dysregulated in breast cancer progression and are one of the causes of resistance to treatment in breast cancer. Furthermore, FGFR signalling on epithelial cells is affected by signals from the breast microenvironment, therefore increasing the possibility of breast developmental abnormalities or cancer progression. Increasing our understanding of the multi-layered roles of the complex family of FGFRs, their ligands FGFs and their regulatory partners may offer novel treatment strategies for breast cancer patients, as a single agent or rational co-target, which will be explored in depth in this review.

Effects of Na+ channel isoforms and cellular environment on temperature tolerance of cardiac Na+ current in zebrafish (Danio rerio) and rainbow trout (Oncorhynchus mykiss)

Heat tolerance of heart rate in fish is suggested to be limited by impaired electrical excitation of the ventricle due to the antagonistic effects of high temperature on Na+ (INa) and K+ (IK1) ion currents (INa is depressed at high temperatures while IK1 is resistant to them). To examine the role of Na+ channel proteins in heat tolerance of INa, we compared temperature dependencies of zebrafish (Danio rerio, warm-dwelling subtropical species) and rainbow trout (Oncorhynchus mykiss, cold-active temperate species) ventricular INa, and INa generated by the cloned zebrafish and rainbow trout NaV1.4 and NaV1.5 Na+ channels in human embryonic kidney (HEK) cells. Whole-cell patch-clamp recordings showed that zebrafish ventricular INa has better heat tolerance and slower inactivation kinetics than rainbow trout ventricular INa. In contrast, heat tolerance and inactivation kinetics of zebrafish and rainbow trout NaV1.4 channels are similar when expressed in the identical cellular environment of HEK cells. The same applies to NaV1.5 channels. These findings indicate that thermal adaptation of ventricular INa is largely achieved by differential expression of Na+ channel alpha subunits: zebrafish that tolerate higher temperatures mainly express the slower NaV1.5 isoform, while rainbow trout that prefer cold waters mainly express the faster NaV1.4 isoform. Differences in elasticity (stiffness) of the lipid bilayer and/or accessory protein subunits of the channel assembly may also be involved in thermal adaptation of INa. The results are consistent with the hypothesis that slow Na+ channel kinetics are associated with increased heat tolerance of cardiac excitation.

Possible inhibition mechanism of dobutamine hydrochloride as potent inhibitor for human glucose-6-phosphate dehydrogenase enzyme

Glucose-6-phosphate dehydrogenase (G6PD) is the first rate-limiting enzyme in the pentose phosphate pathway. One of the enzyme's most important functions is the production of a reducing agent that is essential for preserving the level of reduced glutathione (GSH). However, some chemicals, such as industrial waste and the active ingredients of several drugs, can cause reduction or blockage in this enzyme's activity. This case causes the occurrence of anemia by damaging erythrocytes. In this study, the G6PD enzyme was purified 21,981 fold with affinity chromatography and the effects of the active ingredients of some antiarrhythmic drugs on enzyme activity were investigated with in vitro and in silico methods. We found that dobutamine hydrochloride significantly decreased enzyme activity and its inhibitory constant (K_i) value was calculated as 19.02 ± 4.83 mM. The in vitro study results also show that dobutamine hydrochloride is a potent inhibitor of enzyme activity. We also found that dobutamine hydrochloride inhibits the hG6PD enzyme's activity by causing structural alterations in substrate and coenzyme binding sites.Communicated by Ramaswamy H. Sarma.