Genetic disruption of ATAT1 causes RhoA downregulation through abnormal truncation of C/EBPß.

Microtubule acetylation has been shown to regulate actin filament dynamics by modulating signaling pathways that control actin organization, although the precise mechanisms remain unknown. In this study, we found that the downregulation of microtubule acetylation via the disruption ATAT1 (which encodes α-tubulin N-acetyltransferase 1) inhibited the expression of RhoA, a small GTPase involved in regulating the organization of actin filaments and the formation of stress fibers. Analysis of RHOA promoter and chromatin immunoprecipitation assays revealed that C/EBPß is a major regulator of RHOA expression. Interestingly, the majority of C/EBPß in ATAT1 knockout (KO) cells was found in the nucleus as a 27-kDa fragment (referred to as C/EBPßp27) lacking the N-terminus of C/EBPß. Overexpression of a gene encoding a C/EBPßp27-mimicking protein via an N-terminal deletion in C/EBPß led to competitive binding with wild-type C/EBPß at the C/EBPß binding site in the RHOA promoter, resulting in a significant decrease of RHOA expression. We also found that cathepsin L (CTSL), which is overexpressed in ATAT1 KO cells, is responsible for C/EBPßp27 formation in the nucleus. Treatment with a CTSL inhibitor led to the restoration of RHOA expression by downregulation of C/EBPßp27 and the invasive ability of ATAT1 KO MDA-MB-231 breast cancer cells. Collectively, our findings suggest that the downregulation of microtubule acetylation associated with ATAT1 deficiency suppresses RHOA expression by forming C/EBPßp27 in the nucleus through CTSL. We propose that CTSL and C/EBPßp27 may represent a novel therapeutic target for breast cancer treatment. [BMB Reports 2024; 57(6): 293-298].

Understanding the pharmacokinetic journey of Fc-fusion protein, rhIL-7-hyFc using complementary approach of two analytical methods, accelerator mass spectrometry and ELISA.

Antibody-based therapeutics (ABTs), including monoclonal/polyclonal antibodies and fragment crystallizable region (Fc)-fusion proteins, are increasingly used in disease treatment, driving the global market growth. Understanding the pharmacokinetic (PK) properties of ABTs is crucial for their clinical effectiveness. This study investigated the PK profile and tissue distribution of efineptakin alfa, a long-acting recombinant human interleukin-7 (rhIL-7-hyFc), using enzyme-linked immunosorbent assay (ELISA) and accelerator mass spectrometry (AMS). Totally, four rats were injected intramuscularly with 1 mg/kg of rhIL-7-hyFc containing 14C-rhIL-7-hyFc, which was prepared via reductive methylation. Serum total radioactivity (TRA) and serum rhIL-7-hyFc concentrations were quantified using AMS and ELISA, respectively. The TRA concentrations in organs were determined by AMS. Serum TRA peaked at 10 hours with a terminal half-life of 40 hours. The rhIL-7-hyFc exhibited a mean peak concentration at around 17 hours and a rapid elimination with a half-life of 12.3 hours. Peak concentration and area under the curve of TRA were higher than those of rhIL-7-hyFc. Tissue distribution analysis showed an elevated TRA concentrations in lymph nodes, kidneys, and spleen, indicating rhIL-7-hyFc's affinity for these organs. The study also simulated the positions of 14C labeling in rhIL-7-hyFc, identifying specific residues in the fragment of rhIL-7 portion, and provided the explanation of distinct analytes targeted by each method. Combining ELISA and AMS provided advantages by offering sensitivity and specificity for quantification as well as enabling the identification of analyte forms. The integrated use of ELISA and AMS offers valuable insights for the development and optimization of ABT.

Microtubule acetylation induced by oxidative stress regulates subcellular distribution of lysosomal vesicles for amyloid-beta secretion.

Excessive production and accumulation of amyloid-beta (Aß) in the brain are one of the hallmarks of Alzheimer's disease (AD). Although oxidative stress is known to trigger and promote the progression of AD, the molecular relationship between oxidative stress and Aß production is not yet fully understood. In this study, we demonstrate that microtubule acetylation induced by oxidative stress plays a critical role in Aß production and secretion by altering the subcellular distribution of Aß precursor protein (APP)-containing lysosomal vesicles. Under oxidative stress, both H4-APPSwe/Ind and HEK293T-APPSwe/Ind cell lines showed increased microtubule acetylation and Aß secretion. Knockdown (KD) of alpha-tubulin N-acetyltransferase 1 (ATAT1) by using a lentiviral shRNA not only inhibited the generation of intermediate APP fragments, such as ß-CTF and AICD, but also suppressed Aß secretion. Oxidative stress promoted the dispersion of LAMP1-positive vesicles to the periphery of the cell through microtubule acetylation, leading to the formation of neutralized lysosomal vesicles (NLVs), which was inhibited by ATAT1 KD. Treatment of the cells with the dynein ATPase inhibitor EHNA or downregulation of LIS1, a regulator of dynein-mediated intracellular transport, increased the peripheral localization of NLVs and promoted Aß secretion, whereas KD of ADP ribosylation factor like GTPase 8B showed the opposite result. ATAT1 KD in the hippocampal region of the 5×FAD AD mouse model also showed significant reductions in Aß plaque accumulation and memory loss. Taken together, these findings suggest that oxidative stress-induced microtubule acetylation promotes the peripheral localization of lysosomal vesicles to form NLVs, thereby enhancing Aß secretion.

Downregulation of AP1S1 causes the lysosomal degradation of EGFR in non-small cell lung cancer.

Matrix stiffness has been shown to play a critical role in cancer progression by influencing various cellular processes, including epidermal growth factor (EGF) signaling. However, the underlying molecular mechanisms are not fully understood. Here, we investigated the role of adaptor-related protein complex 1 subunit sigma 1 (AP1S1), a component of adaptor protein complex-1, in the regulation of EGF receptor (EGFR) intracellular trafficking during cancer cell progression. We found that AP1S1 expression was upregulated under stiff matrix conditions, resulting in the regulation of EGFR trafficking in non-small cell lung adenocarcinoma cells. Knockout of AP1S1 caused the lysosomal degradation of EGFR, leading to suppressed EGF-induced anaplastic lymphoma receptor tyrosine kinase phosphorylation. In addition, the downregulation of AP1S1 increased the sensitivity of H1975 cancer cells, which are resistant to tyrosine kinase inhibitors, to erlotinib. Collectively, our results suggest that AP1S1 could regulate EGFR recycling under stiff matrix conditions, and AP1S1 inhibition could be a novel strategy for treating cancer cells resistant to EGFR-targeted anticancer drugs.

Microtubule Acetylation Controls MDA-MB-231 Breast Cancer Cell Invasion through the Modulation of Endoplasmic Reticulum Stress.

During aggressive cancer progression, cancer cells adapt to unique microenvironments by withstanding various cellular stresses, including endoplasmic reticulum (ER) stress. However, the mechanism whereby cancer cells overcome the ER stress to survive remains to be elucidated. Herein, we demonstrated that microtubule acetylation in cancer cells grown on a stiff matrix promotes cancer progression by preventing excessive ER stress. Downregulation of microtubule acetylation using shRNA or CRSIPR/Cas9 techniques targeting ATAT1, which encodes α-tubulin N-acetyltransferase (αTAT1), resulted in the upregulation of ER stress markers, changes in ER morphology, and enhanced tunicamycin-induced UPR signaling in cancer cells. A set of genes involved in cancer progression, especially focal adhesion genes, were downregulated in both ATAT1-knockout and tunicamycin-treated cells, whereas ATAT1 overexpression restored the gene expression inhibited by tunicamycin. Finally, the expression of ATAT1 and ER stress marker genes were negatively correlated in various breast cancer types. Taken together, our results suggest that disruption of microtubule acetylation is a potent therapeutic tool for preventing breast cancer progression through the upregulation of ER stress. Moreover, ATAT1 and ER stress marker genes may be useful diagnostic markers in various breast cancer types.

Cyclin Y, a novel actin-binding protein, regulates spine plasticity through the cofilin-actin pathway.

While positive regulators of hippocampal long-term potentiation (LTP) have extensively been investigated, relatively little is known about the inhibitory regulators of LTP. We previously reported that Cyclin Y (CCNY), a member of cyclin family generally known to function in proliferating cells, is a novel postsynaptic protein that serves as a negative regulator of functional LTP. However, whether CCNY plays a role in structural LTP, which is mechanistically linked to functional LTP, and which mechanisms are involved in the CCNY-mediated suppression of LTP at the molecular level remain elusive. Here, we report that CCNY negatively regulates the plasticity-induced changes in spine morphology through the control of actin dynamics. We observed that CCNY directly binds to filamentous actin and interferes with LTP-induced actin polymerization as well as depolymerization by blocking the activation of cofilin, an actin-depolymerizing factor, thus resulting in less plastic spines and the impairment of structural LTP. These data suggest that CCNY acts as an inhibitory regulator for both structural and functional LTP by modulating actin dynamics through the cofilin-actin pathway. Collectively, our findings provide a mechanistic insight into the inhibitory modulation of hippocampal LTP by CCNY, highlighting a novel function of a cyclin family protein in non-proliferating neuronal cells.

Aptamer-based competitive binding assay for one-step quantitation of hepatitis B surface antigen.

An aptamer-based competitive binding assay for one-step (i.e. no requirement of pre-treatment) quantitation of target molecules of interest has been developed. This method has been successfully employed for the fast and sensitive detection of the surface antigen of the hepatitis B virus (HBsAg). The key features of our method include its low intrinsic background noise, low costs, high resolution, and high sensitivity, enabling the detection of as low as 1.25 mIU mL(-1), approximately 40-fold better than that of the most widely used Abbott Architect assay for HBsAg detection, without the tedious extraction and/or washing procedures. Moreover, this assay has better recovery and accuracy than that of conventional competitive binding assay or others for HBsAg quantitation.