N-terminal acetylation modulates Bax targeting to mitochondria

The role of N-acetyltransferases in cancers

Cancer is a major global health problem that disrupts the balance of normal cellular growth and behavior. Mounting evidence has shown that epigenetic modification, specifically N-terminal acetylation, play a crucial role in the regulation of cell growth and function. Acetylation is a co- or post-translational modification to regulate important cellular progresses such as cell proliferation, cell cycle progress, and energy metabolism. Recently, N-acetyltransferases (NATs), enzymes responsible for acetylation, regulate signal transduction pathway in various cancers including hepatocellular carcinoma, breast cancer, lung cancer, colorectal cancer and prostate cancer. In this review, we clarify the regulatory role of NATs in cancer progression, such as cell proliferation, metastasis, cell apoptosis, autophagy, cell cycle arrest and energy metabolism. Furthermore, the mechanism of NATs on cancer remains to be further studied, and few drugs have been developed. This provides us with a new idea that targeting acetylation, especially NAT-mediated acetylation, may be an attractive way for inhibiting cancer progression.

Shenqisherong pill ameliorates neuronal apoptosis by inhibiting the JNK/caspase-3 signaling pathway in a rat model of cervical cord compression

ETHNOPHARMACOLOGICAL RELEVANCE

The Shenqisherong (SQSR) pill is an empirical prescription of traditional Chinese medicine (TCM), which originated from the National Chinese Medical Science Master, Shi Qi. It has been widely used in the treatment of cervical spondylotic myelopathy (CSM) and promote the recovery of spinal cord function, but underlying molecular mechanism remains unclear.

AIM OF THE STUDY

The objective of this study was to confirm the neuroprotective effects of the SQSR pill.

MATERIALS AND METHODS

A rat model of chronic compression at double-level cervical cord was used in vivo. The protective role of SQSR pill on CSM rats was measured by Basso, Beattie, and Bresnahan (BBB) locomotor scale, inclined plane test, forelimb grip strength assessment, hindlimb pain threshold assessment, and gait analysis. The levels of reactive oxygen species (ROS) were examined by Dihydroethidium (DHE) staining and 2',7'-Dichlorofluorescein (DCF) assay, and apoptosis was detected by TdT-mediated dUTP nick-end labeling (TUNEL) assay. The expression of apoptosis proteins was evaluated by immunofluorescence staining and Western blot.

RESULTS

SQSR pill could facilitate locomotor function recovery in rats with chronic cervical cord compression, reduce local ROS in the spinal cord and downregulate the c-Jun-N-terminal kinase (JNK)/caspase-3 signaling pathway. In addition, the SQSR pill could protect primary rat cortical neurons from glutamate-treated toxicity in vitro by reducing the ROS and downregulating the phosphorylation of JNK and its downstream factors related to neuronal apoptosis meditated by the caspase cascade. Then, the neuroprotective effect was counteracted by a JNK activator.

CONCLUSIONS

Together, SQSR pill could ameliorate neuronal apoptosis by restraining ROS accumulation and inhibiting the JNK/caspase-3 signaling pathway, indicating that SQSR pill could be a candidate drug for CSM.

N-acetyltransferase and inflammation: Bridging an unexplored niche

Protein N-terminal (Nt) acetylation is an essential post-translational process catalysed by N-acetyltransferases or N-terminal acetyltransferases (NATs). Over the past several decades, several types of NATs (NatA- NatH) have been identified along with their substrates, explaining their significance in eukaryotes. It affects protein stability, protein degradation, protein translocation, and protein-protein interaction. NATs have recently drawn attention as they are associated with the pathogenesis of human diseases. In particular, NAT-induced epigenetic modifications play an important role in the control of mitochondrial function, which may lead to inflammatory diseases. NatC knockdown causes a marked reduction in mitochondrial membrane proteins, impairing their functions, and NatA affects mitophagy via reduced phosphorylation and transcription of the autophagy receptor. However, the NAT-mediated mitochondrial epigenetic mechanisms involved in the inflammatory process remain unexplored. The current review will impart an overview of the biological functions and aberrations of various NAT, which may provide a novel therapeutic strategy for inflammatory disorders.

Acetic acid triggers cytochrome c release in yeast heterologously expressing human Bax

Proteins of the Bcl-2 protein family, including pro-apoptotic Bax and anti-apoptotic Bcl-xL, are critical for mitochondrial-mediated apoptosis regulation. Since yeast lacks obvious orthologs of Bcl-2 family members, heterologous expression of these proteins has been used to investigate their molecular and functional aspects. Active Bax is involved in the formation of mitochondrial outer membrane pores, through which cytochrome c (cyt c) is released, triggering a cascade of downstream apoptotic events. However, when in its inactive form, Bax is largely cytosolic or weakly bound to mitochondria. Given the central role of Bax in apoptosis, studies aiming to understand its regulation are of paramount importance towards its exploitation as a therapeutic target. So far, studies taking advantage of heterologous expression of human Bax in yeast to unveil regulation of Bax activation have relied on the use of artificial mutated or mitochondrial tagged Bax for its activation, rather than the wild type Bax (Bax α). Here, we found that cell death could be triggered in yeast cells heterologoulsy expressing Bax α with concentrations of acetic acid that are not lethal to wild type cells. This was associated with Bax mitochondrial translocation and cyt c release, closely resembling the natural Bax function in the cellular context. This regulated cell death process was reverted by co-expression with Bcl-xL, but not with Bcl-xLΔC, and in the absence of Rim11p, the yeast ortholog of mammalian GSK3β. This novel system mimics human Bax α regulation by GSK3β and can therefore be used as a platform to uncover novel Bax regulators and explore its therapeutic modulation.

Knockdown of NAA25 Suppresses Breast Cancer Progression by Regulating Apoptosis and Cell Cycle

NAA25 gene variants were reported as risk factors for type 1 diabetes, rheumatoid arthritis and acute arterial stroke. But it’s unknown whether it could contribute to breast cancer. We identified rs11066150 in lncHSAT164, which contributes to breast cancer, in our earlier genome-wide long non-coding RNA association study on Han Chinese women. However, rs11066150 A/G variant is also located in NAA25 intron. Based on the public database, such as TCGA and Curtis dataset, NAA25 gene is highly expressed in breast cancer tissues and this result has also been proved in our samples and cell lines through RT-qPCR and western blot analysis. To better understand the function of NAA25 in breast cancer, we knocked down the expression of NAA25 in breast cancer cell lines, FACS was used to detect cell apoptosis and cell cycle and colony formation assay was used to detect cell proliferation. We found that NAA25-deficient cells could increase cell apoptosis, delay G2/M phase cell and decrease cell clone formation. RNA sequencing was then applied to analyze the molecular profiles of NAA25−deficient cells, and compared to the control group, NAA25 knockdown could activate apoptosis-related pathways, reduce the activation of tumor-associated signaling pathways and decrease immune response-associated pathways. Additionally, RT-qPCR was employed to validate these results. Taken together, our results revealed that NAA25 was highly expressed in breast cancer, and NAA25 knockdown might serve as a therapeutic target in breast cancer.

Stablization of ACOs by NatB mediated N-terminal acetylation is required for ethylene homeostasis

N-terminal acetylation (NTA) is a highly abundant protein modification catalyzed by N-terminal acetyltransferases (NATs) in eukaryotes. However, the plant NATs and their biological functions have been poorly explored. Here we reveal that loss of function of CKRC3 and NBC-1, the auxiliary subunit (Naa25) and catalytic subunit (Naa20) of Arabidopsis NatB, respectively, led to defects in skotomorphogenesis and triple responses of ethylene. Proteome profiling and WB test revealed that the 1-amincyclopropane-1-carboxylate oxidase (ACO, catalyzing the last step of ethylene biosynthesis pathway) activity was significantly down-regulated in natb mutants, leading to reduced endogenous ethylene content. The defective phenotypes could be fully rescued by application of exogenous ethylene, but less by its precursor ACC. The present results reveal a previously unknown regulation mechanism at the co-translational protein level for ethylene homeostasis, in which the NatB-mediated NTA of ACOs render them an intracellular stability to maintain ethylene homeostasis for normal growth and responses.

Integrated analysis of potential pathways by which aloe-emodin induces the apoptosis of colon cancer cells

Background

Colon cancer is a malignant gastrointestinal tumour with high incidence, mortality and metastasis rates worldwide. Aloe-emodin is a monomer compound derived from hydroxyanthraquinone. Aloe-emodin produces a wide range of antitumour effects and is produced by rhubarb, aloe and other herbs. However, the mechanism by which aloe-emodin influences colon cancer is still unclear. We hope these findings will lead to the development of a new therapeutic strategy for the treatment of colon cancer in the clinic.

Methods

We identified the overlapping targets of aloe-emodin and colon cancer and performed protein–protein interaction (PPI), Gene Ontology (GO), and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses. In addition, we selected apoptosis pathways for experimental verification with cell viability, cell proliferation, caspase-3 activity, DAPI staining, cell cycle and western blotting analyses to evaluate the apoptotic effect of aloe-emodin on colon cancer cells.

Results

The MTT assay and cell colony formation assay showed that aloe-emodin inhibited cell proliferation. DAPI staining confirmed that aloe-emodin induced apoptosis. Aloe-emodin upregulated the protein level of Bax and decreased the expression of Bcl-2, which activates caspase-3 and caspase-9. Furthermore, the protein expression level of cytochrome C increased in a time-dependent manner in the cytoplasm but decreased in a time-dependent manner in the mitochondria.

Conclusion

These results indicate that aloe-emodin may induce the apoptosis of human colon cancer cells through mitochondria-related pathways.

The relationship between endoplasmic reticulum stress and autophagy in apoptosis of BEAS-2B cells induced by cigarette smoke condensate

Cigarette smoke (CS) is one of the severe risk factors for the development of the pulmonary disease. However, the underlying mechanisms, especially the CS-induced the human bronchial epithelial cells (BEAS-2B) apoptosis related to endoplasmic reticulum stress (ERS) and autophagy, remains to be studied. This study aims to investigate the relationship between ERS and autophagy in apoptosis induced by CS condensate (CSC). BEAS-2B cells were stimulated with 0.02, 0.04 and 0.08 mg/ml CSC for 24 h to detect the ERS, autophagy and apoptosis. Then, ERS and autophagy of BEAS-2B cells were inhibited, respectively, by using 4-PBA and 3-MA, and followed by CSC treatment. The results showed that CSC decreased cell viability, increased cell apoptosis, elevated cleaved-caspase 3/pro-caspase 3 ratio and Bax expressions, but decreased Bcl-2 expressions. The GRP78 and CHOP expressions and LC3-II/LC3-I ratio were dose-dependently increased. The structure of the endoplasmic reticulum was abnormal and the number of autolysosomes was increased in BEAS-2B cells after CSC stimulation. The LC3-II/LC3-I ratio was decreased after ERS inhibition with 4-PBA, but GRP78 and CHOP expressions were enhanced after autophagy inhibition with 3-MA. CSC-induced apoptosis was further increased, Bax expressions and cleaved-caspase 3/pro-caspase 3 ratio were improved, but Bcl-2 expressions were decreased after 3-MA or 4-PBA treatment. In conclusion, the study indicates that ERS may repress apoptosis of BEAS-2B cells induced by CSC via activating autophagy, but autophagy relieves ERS in a negative feedback. This study provides better understanding and experimental support on the underlying mechanisms of pulmonary disease stimulated by CS.

Reconstituting the Mammalian Apoptotic Switch in Yeast

Proteins of the Bcl-2 family regulate the permeabilization of the mitochondrial outer membrane that represents a crucial irreversible step in the process of induction of apoptosis in mammalian cells. The family consists of both proapoptotic proteins that facilitate the membrane permeabilization and antiapoptotic proteins that prevent it in the absence of an apoptotic signal. The molecular mechanisms, by which these proteins interact with each other and with the mitochondrial membranes, however, remain under dispute. Although yeast do not have apparent homologues of these apoptotic regulators, yeast cells expressing mammalian members of the Bcl-2 family have proved to be a valuable model system, in which action of these proteins can be effectively studied. This review focuses on modeling the activity of proapoptotic as well as antiapoptotic proteins of the Bcl-2 family in yeast.

Potential Analysis and Preparation of Chitosan Oligosaccharides as Oral Nutritional Supplements of Cancer Adjuvant Therapy

Cancer is considered to have an adverse influence on health around the world. Chitosan, a linear polysaccharide that contains copolymers of β-1-4 linked d-glucosamine and N-acetyl-d-glucosamine units, has been widely used in the field of biomedicine, owing to its nontoxicity, biocompatibility, biodegradability, and hemocompatibility. This study was aimed at preparing the chitosan oligosaccharides (COS) and examining its ability on suppressing lung cancer in vitro and in vivo. Human non-small-cell lung cancer A549 cells model and C57BL/6 mice bearing lung cancer model were adopted. COS showed inhibition on the viability and proliferation of lung carcinoma cells (A549) in time-dependent manners, but no cytotoxicity to human liver cell (HL-7702). Moreover, COS could significantly increase Bax expression of A549 cells while decreasing Bcl-2 expression. COS supplementation significantly inhibited the growth of Lewis tissues and promoted necrosis of tumor cells in vivo. After treatment with COS, significantly elevated concentrations of Bax and reduced expression of Bcl-2 in tumor tissues, as well as elevated levels of TNF-α, IL-2, Fas and Fas-L in mice serum were observed (p < 0.05). In conclusion, COS had certain anti-tumor effects and potential application as a synergic functional food ingredient to prevent cancer.