Activation of Esterase D by FPD5 Inhibits Growth of A549 Lung Cancer Cells via JAB1/p53 Pathway.

Esterase D (ESD) is widely distributed in mammals, and it plays an important role in drug metabolism, detoxification, and biomarkers and is closely related to the development of tumors. In our previous work, we found that a chemical small-molecule fluorescent pyrazoline derivative, FPD5, an ESD activator, could inhibit tumor growth by activating ESD, but its molecular mechanism is still unclear. Here, by using RNA interference (RNAi), andco-immunoprecipitation techniques, we found that ESD suppressed the nucleus exportation of p53 through reducing the interaction between p53 and JAB1. The protein level of p53 in the nucleus was upregulated and the downstream targets of p53 were found by Human Gene Expression Array. p53 inhibited the expression of CDCA8 and CDC20. Lastly, the cell cycle of A549 cells was arrested at the G0/G1 phase. Together, our data suggest that ESD inhibited the cancer cell growth by arresting the cell cycle of A549 cells via the JAB1/p53 signaling pathway. Our findings provide a new insight into how to inhibit the growth of lung cancer with the activation of ESD by FPD5.

Esterase D stabilizes FKBP25 to suppress mTORC1.

BACKGROUND: Esterase D (ESD) is a nonspecific esterase that detoxifies formaldehyde. Many reports have stated that ESD activity is associated with a variety of physiological and pathological processes. However, the detailed signaling pathway of ESD remains poorly understood. METHODS: Considering the advantages of the small chemical molecule, our recent work demonstrated that 4-chloro-2-(5-phenyl-1-(pyridin-2-yl)-4,5-dihydro-1H-pyrazol-3-yl) phenol (FPD5) activates ESD, and will be a good tool for studying ESD further. Firstly, we determined the interaction between ESD and FK506 binding protein 25 (FKBP25) by yeast two-hybrid assay and co-immunoprecipitation (CO-IP) and analyzed the phosphorylation levels of mTORC1, P70S6K and 4EBP1 by western blot. Furthermore, we used the sulforhodamine B (SRB) and chick chorioallantoic membrane (CAM) assay to analyze cell viability in vitro and in vivo after treatment with ESD activator FPD5. RESULTS: We screened FKBP25 as a candidate protein to interact with ESD by yeast two-hybrid assay. Then we verified the interaction between ESD and endogenous FKBP25 or ectopically expressed GFP-FKBP25 by CO-IP. Moreover, the N-terminus (1-90 aa) domain of FKBP25 served as the crucial element for their interaction. More importantly, ESD reduced the K48-linked poly-ubiquitin chains of FKBP25 and thus stabilized cytoplasmic FKBP25. ESD also promoted FKBP25 to bind more mTORC1, suppressing the activity of mTORC1. In addition, ESD suppressed tumor cell growth in vitro and in vivo through autophagy. CONCLUSIONS: These findings provide novel evidence for elucidating the molecular mechanism of ESD and ubiquitination of FKBP25 to regulate autophagy and cancer cell growth. The ESD/FKBP25/mTORC1 signaling pathway is involved in inhibiting tumor cell growth via regulating autophagy.

Cytoprotection against Oxidative Stress by Methylnissolin-3-O-ß-d-glucopyranoside from Astragalus membranaceus Mainly via the Activation of the Nrf2/HO-1 Pathway.

Astragalus membranaceus is a famous herb found among medicinal and food plants in East and Southeastern Asia. The Nrf2-ARE assay-guided separation of an extract from Jing liqueur led to the identification of a nontoxic Nrf2 activator, methylnissolin-3-O-ß-d-glucopyranoside (MNG, a component of A. membranaceus). Nrf2 activation by MNG has not been reported before. Using Western Blot, RT-qPCR and imaging, we investigated the cytoprotective effect of MNG against hydrogen peroxide-induced oxidative stress. MNG induced the expression of Nrf2, HO-1 and NQO1, accelerated the translocation of Nrf2 into nuclei, and enhanced the phosphorylation of AKT. The MNG-induced expression of Nrf2, HO-1, and NQO1 were abolished by Nrf2 siRNA, while the MNG-induced expression of Nrf2 and HO-1 was abated and the AKT phosphorylation was blocked by LY294002 (a PI3K inhibitor). MNG reduced intracellular ROS generation. However, the protection of MNG against the H2O2 insult was reversed by Nrf2 siRNA with decreased cell viability. The enhancement of Nrf2 and HO-1 by MNG upon H2O2 injury was reduced by LY294002. These data showed that MNG protected EA.hy926 cells against oxidative damage through the Nrf2/HO-1 and at least partially the PI3K/Akt pathways.

Solution structure and functional characterization of jingzhaotoxin-XI: a novel gating modifier of both potassium and sodium channels.

JZTX-XI is a peptide toxin isolated from the venom of the Chinese spider Chilobrachys jingzhao. It contains 34 residues including six cysteine residues with disulfide bridges linked in the pattern of I-IV, II-V, and III-VI. Using 3'- and 5'-RACE methods, the full-length cDNA was identified as encoding an 86-residue precursor of JZTX-XI. In the electrophysiological assay, JZTX-XI shows activity toward the Kv2.1 channel in a way similar to hanatoxin1 and SGTx1 that both the activation and the deactivation processes are affected, which is in accordance with the high sequence homology among them (over 60% identity). On the other hand, JZTX-XI also exhibits specific interaction against the Nav channels of rat cardiac myocytes with a significant reduction in the peak current and slowing of channel inactivation. The solution structure of native JZTX-XI was determined by 1H NMR methods to identify the structural basis of these specific activities. Structural comparison of JZTX-XI with other gating modifier toxins shows that they all adopt a similar surface profile, a hydrophobic patch surrounded by charged residues such as Arg or Lys, which might be a common structural factor responsible for toxin-channel interaction. JZTX-XI might be an ideal tool to further investigate how spider toxins recognize various ion channels as their targets.

Jingzhaotoxin-III, a novel spider toxin inhibiting activation of voltage-gated sodium channel in rat cardiac myocytes.

We have isolated a cardiotoxin, denoted jingzhaotoxin-III (JZTX-III), from the venom of the Chinese spider Chilobrachys jingzhao. The toxin contains 36 residues stabilized by three intracellular disulfide bridges (I-IV, II-V, and III-VI), assigned by a chemical strategy of partial reduction and sequence analysis. Cloned and sequenced using 3'-rapid amplification of cDNA ends and 5'-rapid amplification of cDNA ends, the full-length cDNA encoded a 63-residue precursor of JZTX-III. Different from other spider peptides, it contains an uncommon endoproteolytic site (-X-Ser-) anterior to mature protein and the intervening regions of 5 residues, which is the smallest in spider toxin cDNAs identified to date. Under whole cell recording, JZTX-III showed no effects on voltage-gated sodium channels (VGSCs) or calcium channels in dorsal root ganglion neurons, whereas it significantly inhibited tetrodotoxin-resistant VGSCs with an IC(50) value of 0.38 microm in rat cardiac myocytes. Different from scorpion beta-toxins, it caused a 10-mV depolarizing shift in the channel activation threshold. The binding site for JZTX-III on VGSCs is further suggested to be site 4 with a simple competitive assay, which at 10 microm eliminated the slowing currents induced by Buthus martensi Karsch I (BMK-I, scorpion alpha-like toxin) completely. JZTX-III shows higher selectivity for VGSC isoforms than other spider toxins affecting VGSCs, and the toxin hopefully represents an important ligand for discriminating cardiac VGSC subtype.