Biology subjects

Kang, B. E.

Publications and source records attributed to Kang, B. E..

5 recordsLinked to original sources

bioRxiv2023

Loss-of-SIRT7 sensitizes hepatocellular carcinoma to sorafenib through the regulation of ERK Phosphorylation

The FDA-approved oral multi-kinase inhibitor, sorafenib (BAY 43-9006, Nexavar), is the first approved systemic therapy for patients with unresectable hepatocellular carcinoma (HCC). Although it has been shown to significantly improve the overall survival of patients with HCC, drug resistance limits the response rate to this therapeutic. Here, we report that acquired sorafenib resistance is associated with overexpression of the deacetylase, SIRT7, and a high level of ERK phosphorylation. Further, we identify that the hyperactivation of ERK is controlled by SIRT7-mediated deacetylation of DDX3X. The inhibition of SIRT7 combined with sorafenib resulted in a marked reduction of cell viability in vitro and of tumor growth in vivo. It seems plausible that SIRT7 is responsible for the acquired sorafenib resistance and its inhibition is most likely beneficial together in conjunction with sorafenib by suppressing ERK signaling. HighlightsO_LISorafenib resistance in HCC is associated with SIRT7 and ERK hyperactivation. C_LIO_LISuppression of SIRT7 combined with sorafenib restores sensitivity to sorafenib. C_LIO_LISIRT7 controls sorafenib resistance through ERK activation by mediating DDX3X deacetylation. C_LI

cancer biology↗

bioRxiv2021

GCN5 Maintains Muscle Integrity by Acetylating YY1 to Promote Dystrophin Expression

This work identifies a novel role for the acetyltransferase GCN5 in regulating muscle integrity through inhibition of DNA binding activity of the transcriptional repressor YY1. Here we report that in mice a muscle-specific knockout of GCN5 (Gcn5skm-/-) reduces the expression of key structural muscle proteins, including dystrophin, resulting in myopathy. Supporting our observation, a meta-analysis between the differential transcriptome of Gcn5skm-/- muscle and all available open-access data sets identified top correlations with musculoskeletal diseases in humans. GCN5 was found to acetylate YY1 at two residues (K392 and K393), which disrupts the interaction between the YY1 zinc-finger region and DNA. De/acetylation mimics for these YY1 post-translational modifications modulated muscle structural gene expression and DNA binding. Analysis of human GTEx data also found positive and negative correlations between fiber diameter and GCN5 and YY1 respectively. Collectively, our results demonstrate that GCN5 acetyltransferase activity regulates YY1 DNA binding and expression of dystrophin to modulate muscle integrity.

cell biology↗

bioRxiv2021

Epigenetic modulation in the pathogenesis and treatment of inherited aortic aneurysm conditions

Shprintzen-Goldberg syndrome (SGS) is a rare systemic connective tissue disorder characterized by craniofacial, skeletal, neurodevelopmental, cutaneous, and cardiovascular manifestations, including aortic root aneurysm. It has significant phenotypic overlap with both Marfan syndrome (MFS) and Loeys-Dietz syndrome (LDS). We previously reported that SGS is caused by heterozygous mutations in the Sloan-Kettering Institute proto-oncogene (SKI), which encodes a potent suppressor of transforming growth factor beta (TGF{beta}) target gene expression. Herein, we show that mouse lines harboring orthologous amino acid substitutions in Ski recapitulate multiple human SGS phenotypic manifestations, including skin collagen deposition, skeletal kyphosis, behavioral hypoactivity, and aortic root aneurysm. Furthermore, aortic root aneurysm in SGS mice is associated with both increased acetylation of histone H3 at lysine-27 (H3K27) and TGF{beta} target gene expression, all of which can be ameliorated by pharmacological CBP/P300 inhibition in vivo; similar findings were seen in cultured dermal fibroblast from SGS patients. Aortic root growth is also abrogated in a mouse model of MFS by selective CBP/P300 inhibition in association with blunted expression of TGF{beta} target genes. These data document excessive H3K27 acetylation and hence TGF{beta} target gene expression in the pathogenesis of inherited presentations of aortic root aneurysm and the therapeutic potential of pharmacological epigenetic modulation.

genetics↗

bioRxiv2020

Proton wires mediate the optical signal for ArcLight-type Genetically Encoded Voltage Indicators

The genetically encoded voltage indicators, ArcLight and its derivatives, mediate voltage dependent optical signals by intermolecular, electrostatic interactions between neighboring fluorescent proteins (FPs) via proton wires. A random mutagenesis event placed a negative charge on the exterior of the FP resulting in a greater than 10-fold improvement of the voltage-dependent optical signal. Repositioning this negative charge on the exterior of the FP reversed the polarity of voltage-dependent optical signals suggesting the presence of hot spots capable of interacting with the negative charge on a neighboring FP thereby changing the fluorescent output. To explore the potential effect on the chromophore state, voltage-clamp fluorometry was performed with alternating excitation at 390 nm followed by excitation at 470 nm resulting in several mutants exhibiting voltage-dependent, ratiometric optical signals of opposing polarities. However, the kinetics, voltage ranges, and optimal FP fusion sites were different depending on the wavelength of excitation. These results suggest that the FP has external, electrostatic pathways capable of quenching fluorescence that are wavelength specific. ArcLight-derived GEVIs may therefore offer a novel way to map how conditions external to the {beta}-can structure can affect the fluorescence of the chromophore and transiently manipulate those pathways via conformational changes mediated by whole cell voltage clamp. Statement of SignificanceArcLight-type GEVIs utilize proton pathways that send charge information outside of the FP to the internal chromophore enabling voltage induced conformational changes to affect fluorescence. These pathways are excitation wavelength specific suggesting that different external positions affect the protonated and deprotonated states of the chromophore.

biophysics↗

bioRxiv2020

Improving the flexibility of Genetically Encoded Voltage Indicators via intermolecular FRET

A new family of Genetically Encoded Voltage Indicators (GEVIs) has been developed based on inter-molecular Forster Resonance Energy Transfer (FRET). To test the hypothesis that the GEVI, ArcLight, functions via interactions between the fluorescent protein (FP) domain of neighboring probes, the FP of ArcLight was replaced with either a FRET donor or acceptor FP. We discovered relatively large FRET signals only when cells were co-transfected with both the FRET donor and acceptor GEVIs. Using a CFP donor and an RFP acceptor, we were able to observe a voltage dependent signal with a Stokes shift of over 200 nm. The intermolecular FRET strategy also works for rhodopsin-based probes potentially improving their flexibility as well. Separating the FRET pair into two distinct proteins has important advantages over intramolecular FRET constructs. First, the signals are larger. Apparently the voltage-induced conformational change moves the two FPs independently thereby increasing the dynamic range. Second, the expression of the FRET donor and acceptor can be restricted independently enabling greater cell type specificity as well as refined subcellular voltage reporting.

neuroscience↗