Biology subjects

Ahn, Y.-H.

Publications and source records attributed to Ahn, Y.-H..

5 recordsLinked to original sources

bioRxiv2026

ARHGEF7 S-glutathionylation promotes cancer cell migration through Rac1 activation

Reactive oxygen species (ROS) are central signaling molecules in many biological processes by inducing oxidative modifications of protein cysteine residues, including S-glutathionylation. Increasing evidence supports that ROS contribute to cancer progression via promoting cancer cell migration, invasion, and metastasis. Nevertheless, the protein targets of S-glutathionylation that regulate cancer cell motility remain ill-defined. In this study, we report on the redox regulation of ARHGEF7, a guanine nucleotide exchange factor highly expressed in metastatic cancer cells, that plays a major role in regulating cell migration. Our data demonstrates that ARHGEF7 is selectively glutathionylated at the highly conserved C312 residue in its PH domain, which is implicated in regulating its enzymatic activity. Breast cancer cell lines showed increased cell migration and invasion upon glutathionylation of ARHGEF7 at C312 in response to both oxidative stress and epidermal growth factor (EGF). Mechanistically, upon C312 glutathionylation, ARHGEF7 exhibited significantly enhanced binding to Rac1 and increased Rac1 recruitment to the cell membrane and lamellipodia. ARHGEF7 S-glutathionylation also increased its enzymatic rate of GDP-GTP nucleotide exchange, resulting in Rac1 activation. Consequently, ARHGEF7 C312 S-glutathionylation induced Rac1-PAK1 activation and their downstream pathways, including LIMK1 and MEK1, thereby enhancing migration and invasion. Our data reveal a new redox player in cell migration, with its potential implications for ROS-induced cancer progression.

biochemistry↗

bioRxiv2025

Redox Regulation of Cell Migration via Nischarin S-glutathionylation

Reactive oxygen species (ROS) are central players in redox signaling, controlling all biological processes in human health. Many reports demonstrated that ROS play essential roles in regulating cell migration and invasion, while contributing to cancer progression and metastasis, potentially via inducing protein cysteine oxidations. Nevertheless, specific redox players involved in cell migration and invasion remain ill-defined. In this report, we found that Nischarin (NISCH), established as a tumor suppressor, is susceptible to S-glutathionylation, selectively at Cys185 located near its leucine-rich repeat (LRR) domains, which are implicated in protein-protein interactions with Rac1 and PAK1. We demonstrated that epithelial breast cancer cell lines, MCF7 and MDA-MB-231, expressing NISCH wild-type (WT), compared to its cysteine mutant (C185S), exhibit increased migration and invasion in response to oxidative stress, such as limited glucose. Mechanistically, NISCH S-glutathionylation reduced its binding to Rac1 and PAK1, without altering its binding to integrin 5. The dissociation of NISCH led to the activation of Rac1 and PAK1, resulting in the localization of Rac1 to the cell periphery, which facilitates lamellipodia formation. The activated PAK1 increased the phosphorylation of the LIMK1-cofilin axis, thereby further enhancing actin filament dynamics that promote cell migration. Based on the mechanistic analysis, we produced an engineered NISCH construct, composed of the N-terminal PX and LRR domains. We demonstrated that the engineered NISCH PX-LRR constructs, particularly one lacking the S-glutathionylation site (i.e., C185S), can suppress the migration, invasion, and colony formation of MDA-MB-231 cells, regardless of the presence of oxidative stress. Our data reports a new redox player in cell migration and invasion, while supporting the potential application of NISCH-derived protein-based therapeutics for breast cancer.

biochemistry↗

bioRxiv2025

FUNCTIONAL ANALYSIS OF BIPARTITE NRF2 ACTIVATORS THAT OVERCOME FEEDBACK REGULATION FOR AGE-RELATED CHRONIC DISEASES

Activating Nrf2 with small molecules is a promising strategy for countering aging, oxidative stress, inflammation, and various disorders, including neurodegeneration. The primary regulator of Nrf2 protein stability is Keap1, a redox sensor protein and an adapter in the Cullin III ubiquitin ligase complex, which labels Nrf2 for proteasomal degradation. The known Nrf2 activators either chemically modify sensor thiols in Keap1 or competitively displace Nrf2 from the ubiquitin ligase complex. The latter approach is considered the most suitable for continuous administration, as non-specific chemical modifiers of Keap1 thiols also modify active thiols on other proteins, thus causing side effects. However, when transitioning from homogeneous to cell-based assays, genuine displacement activators show a significant loss in potency by several orders of magnitude. As we demonstrate here, this offset is due to the presence of high micromolar concentrations of Keap1 in both the cell lines and brain tissue. A potential solution could involve targeted delivery of an alkylating agent to Keap1 to achieve the desired specificity. Transcriptomic analysis of a cell-permeable Nrf2 peptide bearing an alkylating fumarate moiety indicates selective activation of the Nrf2 genetic program, confirming the high specificity of this approach. The Nrf2-triggered genetic program has a feedback regulation mechanism through the activation of Bach1, an Nrf2 transcriptional repressor, which is elevated in age-related neurodegeneration. Thus, a benign bipartite Nrf2 activator with Bach1 inhibition properties is needed for maximal benefits. The recently developed heterocyclic carboxamide, HPPE, shows overlap with the Nrf2 pathway activated by the fumarate-linked Nrf2 peptide and with zinc and tin protoporphyrins, which are recognized inhibitors of Bach1. Therefore, HPPE presents a promising and unique combination of the two desired activities that could be further optimized to treat age-related neurodegeneration. HighlightsO_LIThe decrease in potency for reversible displacement activators of Nrf2 in biological assays is attributed to high micromolar concentrations of Keap1 and competition with endogenous Keap1 client proteins. C_LIO_LINrf2 activators specific for Keap1 should combine a displacement scaffold with a substitution that undergoes intracellular conversion into active pro-oxidant or alkylating species. C_LIO_LICell-permeable fumarate-linked Nrf2 peptide solely activates the Nrf2 antioxidant genetic program, as demonstrated by transcriptomic analysis. C_LIO_LIHPPE, a small bipartite molecule, exhibits properties of both Nrf2 activation and Bach1 inhibition, to bypass feedback regulation by targeting both Keap1 and Bach1. C_LI

biochemistry↗

bioRxiv2024

Impact of Species-Specific Plant Growth-Promoting Rhizobacteria (PGPR) on Maize (Zea mays) Phenotypic and Biochemical Diversity

Maize (Zea mays) is a vital cereal crop used as a staple diet in many countries. In contemporary farming practises, inoculation with plant-growth-promoting rhizobacteria (PGPR) can be promoted as a sustainable alternative to chemical fertilizers and pesticides in cereal crops including maize. For experimental verification of the above-mentioned hypothesis, four PGPR inoculants Pseudomonas fluorescens, P. putida, Azospirillum lipoferum and Bacillus subtilis were applied to three maize genotypes (AXE*, PMH1 and PMH10) and their effects were studied by measurement of various morphological and biochemical paramters. Substantial increase in the amount of chlorophyll a (45%), chlorophyll b (100%), total chlorophyll (95%), nitrate reductase (22%), superoxide dismutase (52%), protein content (16%), methionine content (31.8%), grain protein content (69%) were recorded over the control (non-treated or mock) plants. Morphological parameters also exhibited an increase in leaf number (53%), fresh weight (41%) and dry weight (62%) in test plants. Comparable outcome was observed for whole cob weight showing an increase of 42%, cob weight (60%), hundred-grain weight (25.9%), maize grain yield m-2 (18%) and yield ha-1 (18%) over the control. This study highlights the efficacy of the aforementioned four PGPR species as the most effective for maize crops. Bacillus subtilis and Azospirillum lipoferum may be considered species-specific PGPRs due to their superior performance compared to other strains. The considerable growth-promoting advantages observed in maize plants treated with bacterial inoculation indicated that PGPRs have the potential to be employed as sustainable solutions in maize production.

plant biology↗

bioRxiv2017

Programming of macrophages by apoptotic cancer cells inhibits cancer progression through exosomal PTEN and PPARγ ligands

Apoptotic cell clearance by phagocytes is essential in tissue homeostasis. We demonstrated that conditioned medium (CM) from macrophages exposed to apoptotic cancer cells inhibits epithelial-mesenchymal transition (EMT), migration, and invasion of cancer cells with the acquisition of cancer-stem-like traits. Apoptotic 344SQ (ApoSQ) cell-induced PPAR{gamma} activity in macrophages caused increased PTEN levels, secreted in exosomes. ApoSQ-exposed CM from PTEN knockdown cells failed to enhance PTEN in recipient 344SQ cells, restore cellular polarity, and exert anti-EMT and anti-invasive effects. The CM which deficient of PPAR{gamma} ligands could not reverse the suppression of PPAR{gamma} activity and PTEN and consequently failed to the prevent EMT process. Moreover, single injection of ApoSQ cells inhibited lung metastasis in syngeneic mice with enhanced PPAR{gamma}/PTEN signaling both in tumor-associated macrophages and tumor cells. PPAR{gamma} antagonist GW9662 reversed PTEN signaling and anti-metastatic effect. Thus, apoptotic cancer cell therapy may offer a new strategy for the prevention of metastasis.

cancer biology↗