Spatiotemporal feedforward between PKM2 tetramers and mTORC1 prompts mTORC1 activation.

Most mammalian cells couple glucose availability to anabolic processes via the mTORC1 pathway. However, the mechanism by which fluctuations in glucose availability are rapidly translated into mTORC1 signals remains elusive. Here, we show that cells rapidly respond to changes in glucose availability through the spatial coupling of mTORC1 and tetramers of the key glycolytic enzyme pyruvate kinase M2 (PKM2) on lysosomal surfaces in the late G1/S phases. The lysosomal localization of PKM2 tetramers enables rapid increases in local ATP concentrations around lysosomes to activate mTORC1, while bypassing the need to elevate global ATP levels in the entire cell. In essence, this spatial coupling establishes a feedforward loop to enable mTORC1 to rapidly sense and respond to changes in glucose availability. We further demonstrate that this mechanism ensures robust cell proliferation upon fluctuating glucose availability. Thus, we present mechanistic insights into the rapid response of the mTORC1 pathway to changes in glucose availability. The underlying mechanism may be applicable to the control of other cellular processes.

Glycolytic reprogramming in cancer cells: PKM2 dimer predominance induced by pulsatile PFK-1 activity.

The glycolytic enzyme pyruvate kinase M2 (PKM2) exists in both catalytically inactive dimeric and active tetrameric forms. In cancer cells, PKM2 dimer predominance contributes to tumor growth by triggering glycolytic reprogramming. However, the mechanism that promotes PKM2 dimer predominance over tetramer in cancer cells remains elusive. Here, we show that pulsatile phosphofructokinase (PFK-1) activity results in PKM2 dimer predominance. Mathematical simulations predict that pulsatile PFK-1 activity prevents the formation of PKM2 tetramer even under high levels of fructose-1,6-bisphosphate (FBP), a PKM2 tetramer-promoting metabolite produced by PFK-1. We experimentally confirm these predictions at the single-molecule level by providing evidence for pulsatile PFK-1 activity-induced synchronized dissociation of PKM2 tetramers and the subsequent accumulation of PKM2 dimers under high levels of FBP in HeLa cells. Moreover, we show that pulsatile PFK-1 activity-induced PKM2 dimer predominance also controls cell proliferation. Thus, our study reveals the significance of pulsatile PFK-1 activity in cancer cell metabolism.

Molecular cloning, mRNA expression and alternative splicing of a ryanodine receptor gene from the citrus whitefly, Dialeurodes citri (Ashmead).

Insect ryanodine receptors are the main targets of diamide insecticides that have highly selective insecticidal activity but are less toxic to mammals. Therefore, these insecticides are ideal for pest control. Ryanodine receptors (RyRs) play a critical role in Ca2+ signaling in muscle and non-muscle cells. In this study, we cloned the complete cDNA (DcRyR) of the RyR from the citrus whitefly, Dialeurodes citri, a serious pest of citrus orchards in China. The open reading frame of RyR is 15,378bp long and encodes a protein with 5126 amino acids with a computed molecular weight of 579.523kDa. DcRyR shows a high amino acid sequence identity to RyRs from other insects (76%-95%) and low identity to those from nematodes and mammals (44%-52%). DcRyR shares many features of insect and vertebrate RyRs, including a MIR domain, two RIH domains, three SPRY domains, four copies of RyR repeat domain, RIH-associated domain at the N-terminus, two consensus calcium-binding EF-hands and six transmembrane domains at the C-terminus. The expression of DcRyR mRNA was the highest in the nymphs and lowest in eggs; DcRyR mRNA was 1.85-fold higher in the nymphs than in the eggs. Among the tissues, DcRyR mRNA expression was 4.18- and 4.02-fold higher in the adult head and thorax than in the abdomen. DcRyR had three alternative splice sites and the splice variants showed body part-specific expression and were developmentally regulated. These results may help investigate target-based resistance to diamide insecticides in D. citri.

An increased risk of ovarian cancer associated with polymorphism in BRCC5 gene in Caucasian populations.

Several reports on the association between the BRCC5 gene polymorphism and ovarian cancer risk have been published recently, but the estimates of the risk vary widely. We thus performed a meta-analysis in an effort to determine the association. To identify the eligible studies, we searched the PubMed, Embase, and CNKI databases, and reviewed all original studies retrieved as well as their citations. The risk of ovarian cancer was estimated using odds ratio (OR) and its 95 % confidence interval (CI). Meta-analysis of seven comparisons revealed an obvious rise in the risk of ovarian cancer under the CC vs. GG contrast model (OR = 1.52, 95 % CI = 1.07-2.16, P OR = 0.020). A similar increase was also indicated in the CC vs. GC + GG model (OR = 2.10, 95 % CI = 1.51-2.93, P OR < 0.001). Our meta-analysis indicates that the BRCC5 polymorphism may be a candidate modifier of ovarian cancer risk in Caucasians.

MicroRNA-215 is a potential prognostic marker for cervical cancer.

Recently, microRNAs (miRNAs) have been shown to be involved in multiple biological pathways that can influence tumor progression and metastasis and they can serve as prognostic biomarkers in many cancers. The present study examined the prognostic significance of miR-215 in cervical cancer. The paraffin-embedded paired cervical scrape samples and tumor tissue samples from 302 patients with stage II cervical cancer were detected for the expression of miR-215 by using qRT-PCR. A miR-215-based classifier was established by using the Cox regression model. The prognostic and predictive accuracy of this classifier was determined in both the internal testing group of 138 patients, and the external independent group of 280 patients. Moreover, cervical cancer HeLa cells overexpressing miR-215 (HeLa-miR-215) were constructed and subcutaneously injected into the nude mice to examine the effect of miR-215 on tumor growth and metastasis in vivo. The results showed that the expression level of miR-215 was significantly higher in cervical cancer tissues than in paired normal tissues (P<0.0001). When patients were classified into high- and low-risk cancer progression groups according to miR-215 level, the 5-year disease-free survival in high- and low-risk groups were 43% (95% CI: 32.1-51.6) and 67% (95% CI: 48.6-77.3) (hazard ratio [HR] 2.02, 95% CI: 1.16-3.52; P=0.013) respectively. Moreover, the expression level of miR-215 was negatively associated with survival rate in patients at TNM stage T3 (HR: 3.317; 95% CI: 1.18-5.14, P=0.017) and TNM stage T4 (HR: 3.48; 95% CI: 1.49-4.45, P=0.008). Tumor volume in nude mice injected with HeLa-miR-215 cells was significantly larger than that in mice injected with control HeLa cells. It was concluded that the expression level of miR-215 is associated with cervical tumor progression and worse survival rate, suggesting that it may serve as a potential prognostic marker to identify patients at higher risk of recurrence.

[Single nucleotide polymorphisms of CTLA4 gene and their association with human cervical cancer].

OBJECTIVE: To evaluate the association between single nucleotide polymorphisms (SNPs) of cytotoxic T-lymphocyte-associated protein 4 (CTLA4) gene and susceptibility to cervical cancer. METHODS: One hundred patients and 100 healthy controls from Hubei province were genotyped for 20 polymorphic loci using Sequenom. RESULTS: The frequency of rs11571316 G allele and rs5742909 T allele, which are localized in the promoter region, and rs11571319 A allele, which is downstream of the gene, were significantly higher in patients than in controls. Luciferase assay showed that, as the previously reported rs5742909 T allele, rs11571316 G allele could significantly increase the expression of the reporter gene. CONCLUSION: SNPs in the promoter region of (CTLA4) gene might increase the susceptibility to cervical cancer by increasing (CTLA4) gene expression.

[Effects of quercetin and quercetin in combination with cisplatin on adhesion, migration and invasion of HeLa cells].

OBJECTIVE: To explore the effects of quercetin and quercetin in combination with cisplatin on adhesion, migration and invasion of HeLa cells. METHODS: Adhesion, migration and invasion of HeLa cells treated with quercetin and quercetin in combination with cisplatin were measured by adhesion assay, wound healing assay, and transwell chamber method respectively. RESULTS: The results showed that quercetin and quercetin in combination with cisplatin could inhibit adhesion, migration and invasion of HeLa cells. The adhesive ratio, migration rate and the invasiveness were negatively proportional to concentration of quercetin and quercetin in combination with cisplatin. With increasing concentration of quercetin from 20 to 80 micromol/L, the adhesive ratio decreased from (82.2 +/- 1.5)% to (48.4 +/- 1.1)%; the migration rate decreased from (7.26 +/- 0.20) microm/h to (3.78 +/- 0.64) microm/h; the invasiveness decreased from (124.3 +/- 1.5) piece to (90.7 +/- 2.1) piece (P < 0.05). In quercetin and quercetin in combination with 10 micromol/L cisplatin treatment group, with quercetin concentration increasing from 20 to 80 micromol/L, the adhesive ratio decreased from (42.6 +/- 1.2)% to (27.5 +/- 1.7)%, the migration rate decreased from (2.20 +/- 0.33) microm/h to (0.72 +/- 0.19) microm/h and the invasiveness decreased from (78.7 +/- 2.5) piece to (44.0 +/- 4.0) piece (P < 0.05). Compared with the quercetin groups, quercetin in combination with cisplatin groups had significantly higher inhibitory effects (P < 0.05). CONCLUSIONS: Quercetin and quercetin in combination with cisplatin can inhibit adhesion and migration and invasion of HeLa cells. Quercetin can enhance the inhibitory effect of cisplatin on HeLa cell adhesion, migration and invasion.

Dynamic analysis of optimality in myocardial energy metabolism under normal and ischemic conditions.

To better understand the dynamic regulation of optimality in metabolic networks under perturbed conditions, we reconstruct the energetic-metabolic network in mammalian myocardia using dynamic flux balance analysis (DFBA). Additionally, we modified the optimal objective from the maximization of ATP production to the minimal fluctuation of the profile of metabolite concentration under ischemic conditions, extending the hypothesis of original minimization of metabolic adjustment to create a composite modeling approach called M-DFBA. The simulation results are more consistent with experimental data than are those of the DFBA model, particularly the retentive predominant contribution of fatty acid to oxidative ATP synthesis, the exact mechanism of which has not been elucidated and seems to be unpredictable by the DFBA model. These results suggest that the systemic states of metabolic networks do not always remain optimal, but may become suboptimal when a transient perturbation occurs. This finding supports the relevance of our hypothesis and could contribute to the further exploration of the underlying mechanism of dynamic regulation in metabolic networks.

[In vitro effect of combined traditional Chinese medicine (Changqing capsule) on the tachyzoites of Toxoplasma gondii].

OBJECTIVE: To detect the in vitro effect of the traditional Chinese medicine on the tachyzoites of Toxoplasma gondii. METHODS: Supernatant (1.5 ml) of different doses of the traditional Chinese medicine (Changqing capsule) was collected by normal saline immersion and 2.5 x 10(4) Toxoplasma gondii tachyzoites were added in each paste well for 8 hours. Spiramycin, pyrimethamine and azithromycin in different doses were used as controls. Normal saline was used as negative control. Mice were inoculated with drug-treated tachyzoites intraperitoneally or intragastrically. The normal mice were subcultured after 8 days for 3 generations. RESULTS: The incident number of the infected mice was significantly different among groups with different drugs and doses: 2/60, 16/60, 10/60 and 10/60 in the groups of Changqing capsule, spiramycin, pyrimethamine and azithromycin respectively (P < 0.05). No mice were found incident in groups of high and medium dose Changqing capsule while 2 out of 20 found sick in the low dose group (P < 0.05). The subculture observation showed that 2 and 1 mice in the first generation of the low dose Changqing capsule group inoculated intraperitonelly and intragastrically were found infected respectively. 2 mice of the second generation in low dose spiramycin group and 1 mouse of the third generation in low dose pyrimethamine group were also found infected. CONCLUSION: The in vitro killing effect of the Changqing capsule on the tachyzoites of Toxoplasma gondii is better than the current clinical drugs and shows a positive correlation with the dosages.

Knockdown of survivin contributes to antitumor activity in cisplatin-resistant ovarian cancer cells.

Survivin (SVV) is an important member of the inhibitor of apoptosis family. It is overexpressed in a number of cancer types, including human ovarian carcinomas. SVV promotes invasion, metastasis, growth and survival of malignant cells and confers resistance to specific chemotherapeutic drugs. The present study aimed to elucidate the role and possible mechanisms of SVV in cisplatin-resistant ovarian cancer cells (A2780/CP). Using a loss-of-function approach, we investigated the effects of adenovirus-mediated knockdown of SVV by small hairpin RNA (ad5-SVV) on the expression of pro-caspase-3, cleaved caspase-3, proliferating cell nuclear antigen (PCNA) and matrix metalloproteinase-2 (MMP-2) in A2780/CP cells by real-time PCR and western blot analysis. Proliferation was measured by MTT assay, invasive potential by Transwell, and cell apoptosis by FITC-Annexin V and propidium iodide for the functional analysis of A2780/CP cells following infection with ad5-SVV. As a result, knockdown of SVV downregulated the expression of PCNA and MMP-2 and upregulated the expression of pro-caspase-3 and cleaved caspase-3. In addition, knockdown of SVV enhanced cisplatin-induced proliferative activities, induced cell apoptosis and inhibited the invasive potential in A2780/CP cells. The present findings demonstrate that knockdown of SVV contributes to antitumor activity in cisplatin-resistant ovarian cancer cells via the downregulation of PCNA and MMP-2 expression and the upregulation of caspase-3 expression and indicate that SVV is a potential target for therapeutic anticancer drugs.