Ubiquitin-specific protease 22 acts as an oncoprotein to maintain glioma malignancy through deubiquitinating B cell-specific Moloney murine leukemia virus integration site 1 for stabilization.

Ubiquitin-specific protease 22 (USP22) is a member of the "death-from-cancer" signature, which plays a key role in cancer progression. Previous evidence has shown that USP22 is overexpressed and correlates with poor prognosis in glioma. The effect and mechanism of USP22 in glioma malignancy, especially cancer stemness, remain elusive. Herein, we find USP22 is more enriched in stem-like tumorspheres than differentiated glioma cells. USP22 knockdown inhibits cancer stemness in glioma cell lines. With a cell-penetrating TAT-tag protein, B cell-specific Moloney murine leukemia virus integration site 1 (BMI1), a robust glioma stem-cell marker, is found to mediate the effect of USP22 on glioma stemness. By immunofluorescence, USP22 and BMI1 are found to share similar intranuclear expression in glioma cells. By analysis with immunohistochemistry and bioinformatics, USP22 is found to positively correlate with BMI1 at the post-translational level only rather than at the transcriptional level. By immunoprecipitation and in vivo deubiquitination assay, USP22 is found to interact with and deubiquitinate BMI1 for protein stabilization. Microarray analysis shows that USP22 and BMI1 mutually regulate a series of genes involved in glioma stemness such as POSTN, HEY2, PDGFRA and ATF3. In vivo study with nude mice confirms the role of USP22 in promoting glioma tumorigenesis by regulating BMI1. All these findings indicate USP22 as a novel deubiquitinase of BMI1 in glioma. We propose a working model of the USP22-BMI1 axis, which promotes glioma stemness and tumorigenesis through oncogenic activation. Thus, targeting USP22 might be an effective strategy to treat glioma especially in those with elevated BMI1 expression.

Inhibition of PirB Activity by TAT-PEP Improves Mouse Motor Ability and Cognitive Behavior.

Paired immunoglobulin-like receptor B (PirB), a functional receptor for myelin-associated inhibitory proteins, plays an important role in axon regeneration in injured brains. However, its role in normal brain function with age has not been previously investigated. Therefore in this study, we examined the expression level of PirB in the cerebral cortex, hippocampus and cerebellum of mice at 1 month, 3 months and 18 months of age. The results showed that the expression of PirB increased with age. We further demonstrated that overexpression of PirB inhibited neurite outgrowth in PC12 cells, and this inhibitory activity of PirB could be reversed by TAT-PEP, which is a recombinant soluble PirB ectodomain fused with TAT domain for blood-brain barrier penetration. In vivo study, intraperitoneal administration of TAT-PEP was capable of enhancing motor capacity and spatial learning and memory in mice, which appeared to be mediated through regulation of brain-derived neurotrophic factor (BDNF) secretion. Our study suggests that PirB is associated with aging and TAT-PEP may be a promising therapeutic agent for modulation of age-related motor and cognitive dysfunctions.

Strong inhibition of celastrol towards UDP-glucuronosyl transferase (UGT) 1A6 and 2B7 indicating potential risk of UGT-based herb-drug interaction.

Celastrol, a quinone methide triterpene isolated from Tripterygium wilfordii Hook F., has various biochemical and pharmacological activities, and is now being developed as a promising anti-tumor agent. Inhibitory activity of compounds towards UDP-glucuronosyltransferase (UGT) is an important cause of clinical drug-drug interactions and herb-drug interactions. The aim of the present study is to investigate the inhibition of celastrol towards two important UDP-glucuronosyltransferase (UGT) isoforms UGT1A6 and UGT2B7. Recombinant UGT isoforms and non-specific substrate 4-methylumbelliferone (4-MU) were used. The results showed that celastrol strongly inhibited the UGT1A6 and 2B7-mediated 4-MU glucuronidation reaction, with 0.9 ± 0.1% and 1.8 ± 0.2% residual 4-MU glucuronidation activity at 100 µM of celastrol, respectively. Furthermore, inhibition kinetic study (Dixon plot and Lineweaver-Burk plot) demonstrated that celastrol noncompetitively inhibited the UGT1A1-mediated 4-MU glucuronidation, and competitively inhibited UGT2B7-catalyzed 4-MU glucuronidation. The inhibition kinetic parameters (Ki) were calculated to be 0.49 µM and 0.045 µM for UGT1A6 and UGT2B7, respectively. At the therapeutic concentration of celastrol for anti-tumor utilization, the possibility of celastrol-drug interaction and celastrol-containing herbs-drug interaction were strongly indicated. However, given the complicated nature of herbs, these results should be viewed with more caution.

[Expression and purification of recombinant hypodermin C in Pichia pastoris].

Hypodermin C (HC) cDNA was amplified from recombinant pGEM - T/HC, cloned in frame with the signal sequence in yeast vector pPIC9k. The plasmid was linerarized and transformed into Pichia pastoris GS115 strain by electroporation method. Recombinant strain was screened by G418 resistant, and further confirmed by PCR. The recombinant strain which contains insert was induced in the medium containing 0.5% methanol. The supernatant was collected and then purified by anion exchange chromatography. SDS-PAGE indicated that the target protein is around 28kD. Western-blot showed it can react with rabbit-anti HC serum. Gelatin substrate SDS-PAGE displayed it had enzyme activity. Provided a method to produce enough antigens for carrying out extensive immunological analyses.