Catalytic core function of yeast Pah1 phosphatidate phosphatase reveals structural insight into its membrane localization and activity control

The PAH1-encoded phosphatidate (PA) phosphatase is a major source of diacylglycerol for the production of the storage lipid triacylglycerol and a key regulator for the de novo phospholipid synthesis in Saccharomyces cerevisiae. The catalytic function of Pah1 depends on its membrane localization which is mediated through its phosphorylation by multiple protein kinases and dephosphorylation by the Nem1-Spo7 protein phosphatase complex. The full-length Pah1 is composed of a catalytic core (N-LIP and HAD-like domains, amphipathic helix, and the WRDPLVDID domain) and non-catalytic regulatory sequences (intrinsically disordered regions, RP domain, and acidic tail) for phosphorylation and interaction with Nem1-Spo7. How the catalytic core regulates Pah1 localization and cellular function is not clear. In this work, we analyzed a variant of Pah1 (i.e., Pah1-CC (catalytic core)) that is composed only of the catalytic core. Pah1-CC expressed on a low-copy plasmid complemented the pah1Δ mutant phenotypes (e.g., nuclear/ER membrane expansion, reduced levels of triacylglycerol, and lipid droplet formation) without requiring Nem1-Spo7. The cellular function of Pah1-CC was supported by its PA phosphatase activity mostly associated with the membrane fraction. Although functional, Pah1-CC was distinct from Pah1 in the protein and enzymological properties, which include overexpression toxicity, association with heat shock proteins, and significant reduction of the Vmax value. These findings on the Pah1 catalytic core enhance the understanding of its structural requirements for membrane localization and activity control.

The Saccharomyces cerevisiae Spo7 basic tail is required for Nem1-Spo7/Pah1 phosphatase cascade function in lipid synthesis

The Saccharomyces cerevisiae Nem1-Spo7 protein phosphatase complex dephosphorylates and thereby activates Pah1 at the nuclear/endoplasmic reticulum membrane. Pah1, a phosphatidate phosphatase catalyzing the dephosphorylation of phosphatidate to produce diacylglycerol, is one of the most highly regulated enzymes in lipid metabolism. The diacylglycerol produced in the lipid phosphatase reaction is utilized for the synthesis of triacylglycerol that is stored in lipid droplets. Disruptions of the Nem1-Spo7/Pah1 phosphatase cascade cause a plethora of physiological defects. Spo7, the regulatory subunit of the Nem1-Spo7 complex, is required for the Nem1 catalytic function and interacts with the acidic tail of Pah1. Spo7 contains three conserved homology regions (CR1-3) that are important for the interaction with Nem1, but its region for the interaction with Pah1 is unknown. Here, by deletion and site-specific mutational analyses of Spo7, we revealed that the C-terminal basic tail (residues 240-259) containing five arginine and two lysine residues is important for the Nem1-Spo7 complex-mediated dephosphorylation of Pah1 and its cellular function (triacylglycerol synthesis, lipid droplet formation, maintenance of nuclear/endoplasmic reticulum membrane morphology, and cell growth at elevated temperatures). The glutaraldehyde cross-linking analysis of synthetic peptides indicated that the Spo7 basic tail interacts with the Pah1 acidic tail. This work advances our understanding of the Spo7 function and the Nem1-Spo7/Pah1 phosphatase cascade in yeast lipid synthesis.

Phosphatidate phosphatase Pah1 contains a novel RP domain that regulates its phosphorylation and function in yeast lipid synthesis

The Saccharomyces cerevisiae PAH1-encoded phosphatidate (PA) phosphatase, which catalyzes the Mg2+-dependent dephosphorylation of PA to produce diacylglycerol, is one of the most highly regulated enzymes in lipid metabolism. The enzyme controls whether cells utilize PA to produce membrane phospholipids or the major storage lipid triacylglycerol. PA levels, which are regulated by the enzyme reaction, also control the expression of UASINO-containing phospholipid synthesis genes via the Henry (Opi1/Ino2-Ino4) regulatory circuit. Pah1 function is largely controlled by its cellular location, which is mediated by phosphorylation and dephosphorylation. Multiple phosphorylations sequester Pah1 in the cytosol and protect it from 20S proteasome-mediated degradation. The endoplasmic reticulum-associated Nem1-Spo7 phosphatase complex recruits and dephosphorylates Pah1 allowing the enzyme to associate with and dephosphorylate its membrane-bound substrate PA. Pah1 contains domains/regions that include the N-LIP and haloacid dehalogenase-like catalytic domains, N-terminal amphipathic helix for membrane binding, C-terminal acidic tail for Nem1-Spo7 interaction, and a conserved tryptophan within the WRDPLVDID domain required for enzyme function. Through bioinformatics, molecular genetics, and biochemical approaches, we identified a novel RP (regulation of phosphorylation) domain that regulates the phosphorylation state of Pah1. We showed that the ΔRP mutation results in a 57% reduction in the endogenous phosphorylation of the enzyme (primarily at Ser-511, Ser-602, and Ser-773/Ser-774), an increase in membrane association and PA phosphatase activity, but reduced cellular abundance. This work not only identifies a novel regulatory domain within Pah1 but emphasizes the importance of the phosphorylation-based regulation of Pah1 abundance, location, and function in yeast lipid synthesis.

Conserved regions of the regulatory subunit Spo7 are required for Nem1-Spo7/Pah1 phosphatase cascade function in yeast lipid synthesis

In the yeast Saccharomyces cerevisiae, the Nem1-Spo7 complex is a protein phosphatase that activates Pah1 phosphatidate (PA) phosphatase at the nuclear/endoplasmic reticulum membrane for the synthesis of triacylglycerol. The Nem1-Spo7/Pah1 phosphatase cascade largely controls whether PA is partitioned into the storage lipid triacylglycerol or into membrane phospholipids. The regulated synthesis of the lipids is crucial for diverse physiological processes during cell growth. Spo7 in the protein phosphatase complex is required as a regulatory subunit for the Nem1 catalytic subunit to dephosphorylate Pah1. The regulatory subunit contains three conserved homology regions (CR1, CR2, and CR3). Previous work showed that the hydrophobicity of LLI (residues 54-56) within CR1 is important for Spo7 function in the Nem1-Spo7/Pah1 phosphatase cascade. In this work, by deletion and site-specific mutational analyses, we revealed that CR2 and CR3 are also required for Spo7 function. Mutations in any one of the conserved regions were sufficient to disrupt the function of the Nem1-Spo7 complex. We determined that the uncharged hydrophilicity of STN (residues 141-143) within CR2 was required for Nem1-Spo7 complex formation. Additionally, the hydrophobicity of LL (residues 217 and 219) within CR3 was important for Spo7 stability, which indirectly affected complex formation. Finally, we showed the loss of Spo7 CR2 or CR3 function by the phenotypes (e.g., reduced amounts of triacylglycerol and lipid droplets, temperature sensitivity) that are attributed to defects in membrane translocation and dephosphorylation of Pah1 by the Nem1-Spo7 complex. These findings advance knowledge of the Nem1-Spo7 complex and its role in lipid synthesis regulation.

The Anticancer Drug Bleomycin Shows Potent Antifungal Activity by Altering Phospholipid Biosynthesis

Invasive fungal infections are difficult to treat with limited drug options, mainly because fungi are eukaryotes and share many cellular mechanisms with the human host. Most current antifungal drugs are either fungistatic or highly toxic. Therefore, there is a critical need to identify important fungal specific drug targets for novel antifungal development. Numerous studies have shown the fungal phosphatidylserine (PS) biosynthetic pathway to be a potential target. It is synthesized from CDP-diacylglycerol and serine, and the fungal PS synthesis route is different from that in mammalian cells, in which preexisting phospholipids are utilized to produce PS in a base-exchange reaction. In this study, we utilized a Saccharomyces cerevisiae heterologous expression system to screen for inhibitors of Cryptococcus PS synthase Cho1, a fungi-specific enzyme essential for cell viability. We identified an anticancer compound, bleomycin, as a positive candidate that showed a phospholipid-dependent antifungal effect. Its inhibition on fungal growth can be restored by ethanolamine supplementation. Further exploration of the mechanism of action showed that bleomycin treatment damaged the mitochondrial membrane in yeast cells, leading to increased generation of reactive oxygen species (ROS), whereas supplementation with ethanolamine helped to rescue bleomycin-induced damage. Our results indicate that bleomycin does not specifically inhibit the PS synthase enzyme; however, it may affect phospholipid biosynthesis through disruption of mitochondrial function, namely, the synthesis of phosphatidylethanolamine (PE) and phosphatidylcholine (PC), which helps cells maintain membrane composition and functionality. IMPORTANCE Invasive fungal pathogens cause significant morbidity and mortality, with over 1.5 million deaths annually. Because fungi are eukaryotes that share much of their cellular machinery with the host, our armamentarium of antifungal drugs is highly limited, with only three classes of antifungal drugs available. Drug toxicity and emerging resistance have limited their use. Hence, targeting fungi-specific enzymes that are important for fungal survival, growth, or virulence poses a strategy for novel antifungal development. In this study, we developed a heterologous expression system to screen for chemical compounds with activity against Cryptococcus phosphatidylserine synthase, Cho1, a fungi-specific enzyme that is essential for viability in C. neoformans. We confirmed the feasibility of this screen method and identified a previously unexplored role of the anticancer compound bleomycin in disrupting mitochondrial function and inhibiting phospholipid synthesis.

Glycogen synthase kinase homolog Rim11 regulates lipid synthesis through the phosphorylation of Pah1 phosphatidate phosphatase in yeast

Pah1 phosphatidate (PA) phosphatase plays a major role in triacylglycerol synthesis in Saccharomyces cerevisiae by producing its precursor diacylglycerol and concurrently regulates de novo phospholipid synthesis by consuming its precursor PA. The function of Pah1 requires its membrane localization, which is controlled by its phosphorylation state. Pah1 is dephosphorylated by the Nem1-Spo7 protein phosphatase, whereas its phosphorylation occurs by multiple known and unknown protein kinases. In this work, we show that Rim11, a yeast homolog of mammalian glycogen synthase kinase-3β, is a protein kinase that phosphorylates Pah1 on serine (Ser12, Ser602, and Ser818) and threonine (Thr163, Thr164, Thr522) residues. Enzymological characterization of Rim11 showed that its K_m for Pah1 (0.4 μM) is similar to those of other Pah1-phosphorylating protein kinases, but its K_m for ATP (30 μM) is significantly higher than those of these same kinases. Furthermore, we demonstrate Rim11 phosphorylation of Pah1 does not require substrate prephosphorylation but was increased ∼2-fold upon its prephosphorylation by the Pho85-Pho80 protein kinase. In addition, we show Rim11-phosphorylated Pah1 was a substrate for dephosphorylation by Nem1-Spo7. Finally, we demonstrate the Rim11 phosphorylation of Pah1 exerted an inhibitory effect on its PA phosphatase activity by reduction of its catalytic efficiency. Mutational analysis of the major phosphorylation sites (Thr163, Thr164, and Ser602) indicated that Rim11-mediated phosphorylation at these sites was required to ensure Nem1-Spo7-dependent localization of the enzyme to the membrane. Overall, these findings advance our understanding of the phosphorylation-mediated regulation of Pah1 function in lipid synthesis.

Phosphorylation-mediated regulation of the Nem1-Spo7/Pah1 phosphatase cascade in yeast lipid synthesis

The PAH1-encoded phosphatidate phosphatase, which catalyzes the dephosphorylation of phosphatidate to produce diacylglycerol, controls the divergence of phosphatidate into triacylglycerol synthesis and phospholipid synthesis. Pah1 is inactive in the cytosol as a phosphorylated form and becomes active on the nuclear/endoplasmic reticulum membrane as a dephosphorylated form by the Nem1-Spo7 protein phosphatase complex. The phosphorylation of Pah1 by protein kinases, which include casein kinases I and II, Pho85-Pho80, Cdc28-cyclin B, and protein kinases A and C, controls its cellular location, catalytic activity, and susceptibility to proteasomal degradation. Nem1 (catalytic subunit) and Spo7 (regulatory subunit), which form a protein phosphatase complex catalyzing the dephosphorylation of Pah1 for its activation, are phosphorylated by protein kinases A and C. In this review, we discuss the functions and interrelationships of the protein kinases in the control of the Nem1-Spo7/Pah1 phosphatase cascade and lipid synthesis.

Mutant phosphatidate phosphatase Pah1-W637A exhibits altered phosphorylation, membrane association, and enzyme function in yeast

The Saccharomyces cerevisiae PAH1-encoded phosphatidate (PA) phosphatase, which catalyzes the dephosphorylation of PA to produce diacylglycerol, controls the bifurcation of PA into triacylglycerol synthesis and phospholipid synthesis. Pah1 is inactive in the cytosol as a phosphorylated form and becomes active on the membrane as a dephosphorylated form by the Nem1–Spo7 protein phosphatase. We show that the conserved Trp-637 residue of Pah1, located in the intrinsically disordered region, is required for normal synthesis of membrane phospholipids, sterols, triacylglycerol, and the formation of lipid droplets. Analysis of mutant Pah1-W637A showed that the tryptophan residue is involved in the phosphorylation-mediated/dephosphorylation-mediated membrane association of the enzyme and its catalytic activity. The endogenous phosphorylation of Pah1-W637A was increased at the sites of the N-terminal region but was decreased at the sites of the C-terminal region. The altered phosphorylation correlated with an increase in its membrane association. In addition, membrane-associated PA phosphatase activity in vitro was elevated in cells expressing Pah1-W637A as a result of the increased membrane association of the mutant enzyme. However, the inherent catalytic function of Pah1 was not affected by the W637A mutation. Prediction of Pah1 structure by AlphaFold shows that Trp-637 and the catalytic residues Asp-398 and Asp-400 in the haloacid dehalogenase-like domain almost lie in the same plane, suggesting that these residues are important to properly position the enzyme for substrate recognition at the membrane surface. These findings underscore the importance of Trp-637 in Pah1 regulation by phosphorylation, membrane association of the enzyme, and its function in lipid synthesis.

Public health professionals' perceptions of the capacity of China's CDCs to address emerging and re-emerging infectious diseases

BACKGROUND

China's capacity to control and prevent emerging and re-emerging infectious diseases is critical to the nation's population health. This study aimed to explore the capacity of Centers for Disease Control and Prevention (CDCs) in China to deal with infectious diseases now and in the future.

METHODS

A survey was conducted in 2015 among 973 public health professionals at CDCs in Beijing and four provinces, to assess their capacity to deal with emerging and re-emerging infectious diseases.

RESULTS

Although most professionals were confident with the current capacity of CDCs to cope with outbreaks, nearly all indicated more funding was required to meet future challenges. Responses indicated that Yunnan Province faced more challenges than Anhui, Henan and Liaoning Provinces in being completely prepared and able to deal with outbreaks. Participants aged 20-39 years were more likely than those aged 40 and over to believe strategies such as interdisciplinary and international collaborations for disease surveillance and control, would assist capacity building.

CONCLUSION

The capacity of China's CDCs to deal with infectious diseases was excellent. However, findings suggest it is imperative to increase the number of skilled CDC staff, financial support, and strengthen county level staff training and health education programs.

[Types and treatment of easily-missed, misdiagnosed intestinal obstruction after radical radiotherapy of cervical cancer]

Objective: To investigate the types and treatment methods of easily-missed, misdiagnosed intestinal obstruction after radical radiotherapy of cervical cancer. Methods: The clinical data of 21 patients with intestinal obstruction after radical radiotherapy of cervical cancer in our hospital from May 2013 to May 2019 were collected, including the radiation dose, obstruction symptoms, surgical methods and treatment outcomes. The types and treatment methods of intestinal obstruction after radical radiotherapy of cervical cancer were further investigated. Results: The intestinal obstruction occurred in 21 patients with cervical cancer after radical radiotherapy. All patients were initially diagnosed as rectal obstruction and underwent the transverse colostomy. The obstruction symptoms were successfully resolved in 15 patients while failed in other 6 patients who then underwent the re-operation. Four patients with rectal obstruction accompanied by middle or terminal ileum obstruction underwent ileostomy, the other 2 patients with terminal ileum obstruction underwent the transverse ileal anastomosis and partial intestines exclusion surgery. All of the obstruction symptoms were alleviated. Conclusions: Rectal is the major obstruction site of the cervical cancer patients with intestinal obstruction after radical radiotherapy. However, a possibility of obstruction at the middle or end of the ileum also exists. Therefore, it is very important to avoid misdiagnosis and conduct appropriate operative treatment according to the obstruction site.

[Application of carbon nanoparticles labeled node staining in D2 radical resection of gastric cancer with neoadjuvant chemotherapy]

Objective: To explore the application value of carbon nanoparticles labeled node staining in D2 radical resection of gastric cancer with neoadjuvant chemotherapy. Methods: The retrospective cohort study was conducted. The clinicopathological data of 82 patients with gastric cancer who were admitted to Henan Tumor Hospital from April 2016 to April 2019 were collected. 38 patients who used carbon nanoparticles labeled node staining were in the observation group, while other 44 patients were in the control group. Data analysis including the operation and results of harvested of lymph nodes. Results: All patients successfully completed the operation.Thirty-eight patients successfully completed the injection of carbon nanoparticles. Surgery: observation group operating time was (150±28) min, intraoperative blood loss was (207±121) ml, group operating time was (140±23) min, intraoperative blood loss was (256±182) ml. There was no statistically significant difference between the two groups. Detection of Lymph node: A total of 1 260 lymph nodes were detected in the observation group and 981 in the control group. In the observation group, the mean lymph node sorting time was (17.2±3.3) min, the average number of harvested lymph node was 33.2±10.4, the number of the first station of lymph node was 19.8±5.3, the second station of lymph node was 13.4±6.4, the number of harvested small node(<5 mm) was 673, the positive lymph nodes was 13(range,1-31). They were all higher than those in the control group, which were (20.6±4.4)min,22.3±6.6, 12.6±4.1, 9.7±3.2,432,6 (range,1-13) , respectively. The difference between the two groups was statistically significant (P<0.05). The metastasis rate was 19.1% (241/1 260) in observation group and 16.5%(162/981) in the control group. The difference was no statistical(P>0.05). The rate of black -dyed harvested lymph node was 54.4%(686/1 260) in carbon nanoparticles group. Conclusions: The application of carbon nanoparticles labeled node staining in D2 radical resection of gastric cancer with neoadjuvant chemotherapy is feasible and safe. It can increase the number of lymph nodes detected, which is beneficial to the evaluation of chemotherapy effect and prognosis of patients.

A review of phosphatidate phosphatase assays

Phosphatidate phosphatase (PAP) catalyzes the penultimate step in the synthesis of triacylglycerol and regulates the synthesis of membrane phospholipids. There is much interest in this enzyme because it controls the cellular levels of its substrate, phosphatidate (PA), and product, DAG; defects in the metabolism of these lipid intermediates are the basis for lipid-based diseases such as obesity, lipodystrophy, and inflammation. The measurement of PAP activity is required for studies aimed at understanding its mechanisms of action, how it is regulated, and for screening its activators and/or inhibitors. Enzyme activity is determined through the use of radioactive and nonradioactive assays that measure the product, DAG, or P_i However, sensitivity and ease of use are variable across these methods. This review summarizes approaches to synthesize radioactive PA, to analyze radioactive and nonradioactive products, DAG and P_i, and discusses the advantages and disadvantages of each PAP assay.

Community stakeholder and opinion formation toward end-of-life planning in Chinese community in Australia

We examine the role of stakeholders in constructing new socio-cultural narratives of advance care planning in the Chinese community in Australia. Applying the communication theory of opinion leader(ship) and drawing on data from 41 interviews and field observation notes, we explore how stakeholders establish their authority and perform their expertise. Data analysis shows stakeholders have gained their opinion leadership status through demonstrating their ability to link the Chinese cultural values of family harmony and parental duty and the notions of self-empowerment and independence in official advance care planning promotions in Australia.

The Spo7 sequence LLI is required for Nem1-Spo7/Pah1 phosphatase cascade function in yeast lipid metabolism

The Nem1-Spo7 complex in the yeast Saccharomyces cerevisiae is a protein phosphatase that catalyzes the dephosphory-lation of Pah1 phosphatidate phosphatase, required for its translocation to the nuclear/endoplasmic reticulum membrane. The Nem1-Spo7/Pah1 phosphatase cascade plays a major role in triacylglycerol synthesis and in the regulation of phospholipid synthesis. In this work, we examined Spo7, a regulatory subunit required for Nem1 catalytic function, to identify residues that govern formation of the Nem1-Spo7 complex. By deletion analysis of Spo7, we identified a hydrophobic Leu-Leu-Ile (LLI) sequence comprising residues 54-56 as being required for the protein to complement the temperature-sensitive phenotype of an spo7Δ mutant strain. Mutational analysis of the LLI sequence with alanine and arginine substitutions showed that its overall hydrophobicity is crucial for the formation of the Nem1-Spo7 complex as well as for the Nem1 catalytic function on its substrate, Pah1, in vivo Consistent with the role of the Nem1-Spo7 complex in activating the function of Pah1, we found that the mutational effects of the Spo7 LLI sequence were on the Nem1-Spo7/Pah1 axis that controls lipid synthesis and related cellular processes (e.g. triacylglycerol/phospholipid synthesis, lipid droplet formation, nuclear/endoplasmic reticulum membrane morphology, vacuole fusion, and growth on glycerol medium). These findings advance the understanding of Nem1-Spo7 complex formation and its role in the phosphatase cascade that regulates the function of Pah1 phosphatidate phosphatase.

[Retrospective analysis of curative effect of total pelvic organ resection and anal preservation in 20 patients with recurrence of cervical cancer after radical radiotherapy]

Objective: To explore the surgical method and effect of en bloc pelvic resection and anal preservation after radical radiotherapy for cervical cancer. Methods: Clinical data of 20 cervical cancer patients with central recurrence after radical radiotherapy underwent en bloc pelvic resection in the Tumor Hospital of Zhengzhou University and Hainan Provincial People's Hospital from January 2013 to December 2017 were retrospectively analyzed. The operative time, intraoperative blood loss, length of stay, postoperative anal function and postoperative complications were evaluated. Results: The median operation time of 20 patients with anal preservation after en bloc pelvic resection was 135.2 min, the median intraoperative blood loss was 680 ml, and the median hospitalization time was 16.5 days. Among them, 18 patients had good postoperative healing, and the anal function gradually returned to normal within 6 months after surgery, defecated 1~2 times per day.One patient showed incomplete adhesion between the external colon and the anus. One patient presented with pre-sacral infection. Postoperative pathology confirmed the recurrences in 20 patients, of which 11 cases were squamous cell carcinoma, 7 cases were adenocarcinoma, 2 cases were adenosquamous cell carcinoma. Conclusions: It is safe and reliable to preserve anus after en bloc pelvic resection for cervical cancer patients with radical radiotherapy. The anus function is good enough to improve the postoperative life quality of patients significantly.

[The clinical values of neutrophil-to-lymphocyte ratio as an early predictor of anastomotic leak in postoperative rectal cancer patients]

Objective: To assess the clinical value of neutrophil-to-lymphocyte ratio (NLR) in predicting anastomotic leak of postoperative rectal cancer patients. Methods: The clinical data of 787 rectal cancer patients who underwent anterior resection from January 2014 to December 2017 in Affiliated Tumor Hospital of Zhengzhou University were collected. The postoperative numbers of white blood cell (WBS) on postoperative day (POD)1, 3 and 5 were detected, and the NLR was calculated. The relationship of NLR and the incidence of anastomotic leak was analyzed, and the area under the receiver-operating characteristic (ROC) curves was calculated. The accuracy of postoperative NLR in predicting the incidence of anastomotic leak was evaluated. Results: WBC counts of patients with leak on POD1, POD3 and POD5 were 13.2×10(9)/L, 9.1×10(9)/L and 8.9×10(9)/L, respectively, while those of patients without leak were 12.9×10(9)/L, 9.0×10(9)/L and 8.8×10(9)/L. The WBC count was not significantly different between patients with or without leak (P>0.05). The average NLR values of patients with or without leak were 13.3 and 11.6 on POD1, 10.9 and 7.6 on POD3, 9.3 and 5.3 on POD5, respectively. The NLR values of patients with leak on POD3 and POD5 were significantly higher than those of patients without leak (P<0.05). The cutoff value of NLR on POD3 was 8.6, the sensitivity and specificity of detecting the leakage was 73.2% and 75.6%, respectively, and the area under curve (AUC) was 0.744. The cutoff value of NLR on POD5 was 5.5, the sensitivity and specificity was 69.6% and 75.5%, the AUC was 0.726. The multivariate analysis result showed that NLR >8.6 was an independent factor for anastomotic leak prediction. Conclusion: Postoperative NLR on day 3 is useful in predicting anastomotic leak and can decrease the incidence of complication in rectal cancer patients who underwent anterior resection.

Phosphatidate-mediated regulation of lipid synthesis at the nuclear/endoplasmic reticulum membrane

In yeast and higher eukaryotes, phospholipids and triacylglycerol are derived from phosphatidate at the nuclear/endoplasmic reticulum membrane. In de novo biosynthetic pathways, phosphatidate is channeled into membrane phospholipids via its conversion to CDP-diacylglycerol. Its dephosphorylation to diacylglycerol is required for the synthesis of triacylglycerol as well as for the synthesis of phosphatidylcholine and phosphatidylethanolamine via the Kennedy pathway. In addition to the role of phosphatidate as a precursor, it is a regulatory molecule in the transcriptional control of phospholipid synthesis genes via the Henry regulatory circuit. Pah1 phosphatidate phosphatase and Dgk1 diacylglycerol kinase are key players that function counteractively in the control of the phosphatidate level at the nuclear/endoplasmic reticulum membrane. Loss of Pah1 phosphatidate phosphatase activity not only affects triacylglycerol synthesis but also disturbs the balance of the phosphatidate level, resulting in the alteration of lipid synthesis and related cellular defects. The pah1Δ phenotypes requiring Dgk1 diacylglycerol kinase exemplify the importance of the phosphatidate level in the misregulation of cellular processes. The catalytic function of Pah1 requires its translocation from the cytoplasm to the nuclear/endoplasmic reticulum membrane, which is regulated through its phosphorylation in the cytoplasm by multiple protein kinases as well as through its dephosphorylation by the membrane-associated Nem1-Spo7 protein phosphatase complex. This article is part of a Special Issue entitled Endoplasmic reticulum platforms for lipid dynamics edited by Shamshad Cockcroft and Christopher Stefan.

Yck1 casein kinase I regulates the activity and phosphorylation of Pah1 phosphatidate phosphatase from Saccharomyces cerevisiae

The PAH1-encoded phosphatidate phosphatase in Saccharomyces cerevisiae plays a major role in triacylglycerol synthesis and the control of phospholipid synthesis. For its catalytic function on the nuclear/endoplasmic reticulum membrane, Pah1 translocates to the membrane through its phosphorylation/dephosphorylation. Pah1 phosphorylation on multiple serine/threonine residues is complex and catalyzed by diverse protein kinases. In this work, we demonstrate that Pah1 is phosphorylated by the YCK1-encoded casein kinase I (CKI), regulating Pah1 catalytic activity and phosphorylation. Phosphoamino acid analysis coupled with phosphopeptide mapping of the CKI-phosphorylated Pah1 indicated that it is phosphorylated mainly on multiple serine residues. Using site-directed mutagenesis and phosphorylation analysis of Pah1, we identified eight serine residues (i.e. Ser-114, Ser-475, Ser-511, Ser-602, Ser-677, Ser-705, Ser-748, and Ser-774) as the target sites of CKI. Of these residues, Ser-475 and Ser-511 were specific for CKI, whereas the others were shared by casein kinase II (Ser-705), Cdc28-cyclin B (Ser-602), Pho85-Pho80 (Ser-114, Ser-602, and Ser-748), protein kinase A (Ser-667 and Ser-774), and protein kinase C (Ser-677). CKI-mediated phosphorylation of Pah1 stimulated both its phosphatidate phosphatase activity and its subsequent phosphorylation by casein kinase II. However, the CKI-mediated phosphorylation of Pah1 strongly inhibited its subsequent phosphorylation by Pho85-Pho80, protein kinase A, and protein kinase C. In a reciprocal analysis, Pah1 phosphorylation by Pho85-Pho80 inhibited subsequent phosphorylation by CKI. CKI-mediated Pah1 phosphorylation was also inhibited by a peptide containing the Pah1 residues 506-517, including the kinase-specific Ser-511 residue. These findings advance our understanding of how Pah1 catalytic activity and phosphorylation are regulated by multiple protein kinases.

Protein kinase C mediates the phosphorylation of the Nem1-Spo7 protein phosphatase complex in yeast

The Nem1-Spo7 complex in the yeast Saccharomyces cerevisiae is a protein phosphatase required for the nuclear/endoplasmic reticulum membrane localization of Pah1, a phosphatidate phosphatase that produces diacylglycerol for triacylglycerol synthesis at the expense of phospholipid synthesis. In a previous study, we showed that the protein phosphatase is subject to phosphorylation by protein kinase A (PKA). Here, we demonstrate that Nem1-Spo7 is regulated through its phosphorylation by protein kinase C (PKC), which plays multiple roles, including the regulation of lipid synthesis and cell wall integrity. Phosphorylation analyses of Nem1-Spo7 and its synthetic peptides indicate that both subunits of the complex are bona fide PKC substrates. Site-directed mutagenesis of NEM1 and SPO7, coupled with phosphopeptide mapping and immunoblotting with a phosphoserine-specific PKC substrate antibody, revealed that Ser-201 in Nem1 and Ser-22/Ser-28 in Spo7 are major PKC target sites of phosphorylation. Activity analysis of mutant Nem1-Spo7 complexes indicates that the PKC phosphorylation of Nem1 exerts a stimulatory effect, but the phosphorylation of Spo7 has no effect. Lipid-labeling analysis of cells expressing the phosphorylation-deficient alleles of NEM1 and SPO7 indicates that the stimulation of the Nem1-Spo7 activity has the effect of increasing triacylglycerol synthesis. Prephosphorylation of Nem1-Spo7 by PKC inhibits the PKA phosphorylation of Nem1, whereas prephosphorylation of the phosphatase complex by PKA inhibits the PKC phosphorylation of Spo7. Collectively, this work advances the understanding of the Nem1-Spo7 regulation by phosphorylation and its impact on lipid synthesis.

Casein kinase II-mediated phosphorylation of lipin 1β phosphatidate phosphatase at Ser-285 and Ser-287 regulates its interaction with 14-3-3β protein

The mammalian lipin 1 phosphatidate phosphatase is a key regulatory enzyme in lipid metabolism. By catalyzing phosphatidate dephosphorylation, which produces diacylglycerol, the enzyme plays a major role in the synthesis of triacylglycerol and membrane phospholipids. The importance of lipin 1 to lipid metabolism is exemplified by cellular defects and lipid-based diseases associated with its loss or overexpression. Phosphorylation of lipin 1 governs whether it is associated with the cytoplasm apart from its substrate or with the endoplasmic reticulum membrane where its enzyme reaction occurs. Lipin 1β is phosphorylated on multiple sites, but less than 10% of them are ascribed to a specific protein kinase. Here, we demonstrate that lipin 1β is a bona fide substrate for casein kinase II (CKII), a protein kinase that is essential to viability and cell cycle progression. Phosphoamino acid analysis and phosphopeptide mapping revealed that lipin 1β is phosphorylated by CKII on multiple serine and threonine residues, with the former being major sites. Mutational analysis of lipin 1β and its peptides indicated that Ser-285 and Ser-287 are both phosphorylated by CKII. Substitutions of Ser-285 and Ser-287 with nonphosphorylatable alanine attenuated the interaction of lipin 1β with 14-3-3β protein, a regulatory hub that facilitates the cytoplasmic localization of phosphorylated lipin 1. These findings advance our understanding of how phosphorylation of lipin 1β phosphatidate phosphatase regulates its interaction with 14-3-3β protein and intracellular localization and uncover a mechanism by which CKII regulates cellular physiology.

Phosphatidylserine synthesis is essential for viability of the human fungal pathogen Cryptococcus neoformans

Phospholipids are an integral part of the cellular membrane structure and can be produced by a de novo biosynthetic pathway and, alternatively, by the Kennedy pathway. Studies in several yeast species have shown that the phospholipid phosphatidylserine (PS) is synthesized from CDP-diacylglycerol and serine, a route that is different from its synthesis in mammalian cells, involving a base-exchange reaction from preexisting phospholipids. Fungal-specific PS synthesis has been shown to play an important role in fungal virulence and has been proposed as an attractive drug target. However, PS synthase, which catalyzes this reaction, has not been studied in the human fungal pathogen Cryptococcus neoformans Here, we identified and characterized the PS synthase homolog (Cn Cho1) in this fungus. Heterologous expression of Cn CHO1 in a Saccharomyces cerevisiae cho1Δ mutant rescued the mutant's growth defect in the absence of ethanolamine supplementation. Moreover, an Sc cho1Δ mutant expressing Cn CHO1 had PS synthase activity, confirming that the Cn CHO1 encodes PS synthase. We also found that PS synthase in C. neoformans is localized to the endoplasmic reticulum and that it is essential for mitochondrial function and cell viability. Of note, its deficiency could not be complemented by ethanolamine or choline supplementation for the synthesis of phosphatidylethanolamine (PE) or phosphatidylcholine (PC) via the Kennedy pathway. These findings improve our understanding of phospholipid synthesis in a pathogenic fungus and indicate that PS synthase may be a useful target for antifungal drugs.

Dengue control in the context of climate change: Views from health professionals in different geographic regions of China

BACKGROUND

Dengue is a significant climate-sensitive disease. Public health professionals play an important role in prevention and control of the disease. This study aimed to explore dengue control and prevention in the context of climate change in China.

METHODS

A cross-sectional survey was conducted among 630 public health professionals in 2015. Descriptive analysis and logistic regression were performed.

RESULTS

More than 80% of participants from southwest and central China believed climate change would affect dengue. However, participants from northeast China were less likely to believe so (65%). Sixty-nine percent of participants in Yunnan perceived that dengue had emerged/re-emerged in recent years, compared with 40.6% in Henan and 23.8% in Liaoning. Less than 60% of participants thought current prevention and control programs had been effective. Participants believed mosquitoes in high abundance, imported cases and climate change were main risk factors for dengue in China.

CONCLUSION

There were varying views of dengue in China. Professionals in areas susceptible to dengue were more likely to be concerned about climate change and dengue. Current prevention and control strategies need to be improved. Providing more information for staff in lower levels of Centers for Disease Control and Prevention may help in containing a possible increase of dengue.

Fat-regulating phosphatidic acid phosphatase: a review of its roles and regulation in lipid homeostasis

Phosphatidic acid (PA) phosphatase is an evolutionarily conserved enzyme that plays a major role in lipid homeostasis by controlling the cellular levels of its substrate, PA, and its product, diacylglycerol. These lipids are essential intermediates for the synthesis of triacylglycerol and membrane phospholipids; they also function in lipid signaling, vesicular trafficking, lipid droplet formation, and phospholipid synthesis gene expression. The importance of PA phosphatase to lipid homeostasis and cell physiology is exemplified in yeast, mice, and humans by a host of cellular defects and lipid-based diseases associated with loss or overexpression of the enzyme activity. In this review, we focus on the mode of action and regulation of PA phosphatase in the yeast Saccharomyces cerevisiae The enzyme Pah1 translocates from the cytosol to the nuclear/endoplasmic reticulum membrane through phosphorylation and dephosphorylation. Pah1 phosphorylation is mediated in the cytosol by multiple protein kinases, whereas dephosphorylation is catalyzed on the membrane surface by an integral membrane protein phosphatase. Posttranslational modifications of Pah1 also affect its catalytic activity and susceptibility to degradation by the proteasome. Additional mechanistic understanding of Pah1 regulation should be instrumental for the identification of small-molecule inhibitors or activators that can fine-tune PA phosphatase function and thereby restore lipid homeostasis.

[Surgical resection for gastric cancer patients with liver metastasis]

Objective: To explore the surgical results and clinicopathological features of gastric cancer patients with liver metastases. Methods: The clinicopathological data and post-operative survival of 37 patients who underwent resection of liver metastasis from gastric cancer at our department from Dec. 2007 to Dec. 2014 were analyzed. Results: The 1-, 3-, and 5-year overall survival rates after resection were 91.4%, 57.9%, and 22.0%, respectively, with a median survival of 37 months. Univariate analysis revealed that lymph node metastasis, multiple hepatic metastases and no preoperative chemotherapy are unfavorable prognostic factors for overall survival. Multivariate analysis identified that lymph node metastasis and number of liver metastasis are independent prognostic factors. Conclusions: Gastric cancer patients with a solitary liver metastasis may be good candidates for gastric D2 resection combined with liver R0 resection.

Impact of meteorological factors on hemorrhagic fever with renal syndrome in 19 cities in China, 2005-2014

This study aims to investigate the associations between meteorological factors and hemorrhagic fever with renal syndrome (HFRS) in 19 cities selected from HFRS high risk areas across different climate zones in three Provinces of China. De-identified daily reports of HFRS in Anhui, Heilongjiang, and Liaoning Provinces for 2005-2014 were obtained from the Chinese Center for Disease Control and Prevention. Daily weather data from each study location were obtained from the China meteorological Data Sharing Service System. Generalised estimating equation models (GEE) were used to quantify the city-specific HFRS-weather associations. Multivariate random-effects meta-regression models were used to pool the city-specific HFRS-weather effect estimates. HFRS showed an overall downward trend during the study period with a slight rebound after 2010. Meteorological factors were significantly associated with HFRS incidence. HFRS was relatively more sensitive to weather variability in subtropical regions (Anhui Province) than in temperate regions (Heilongjiang and Liaoning Provinces). The size of effect estimates and the duration of lagged effects varied by locations. Pooled results of the 19 cities showed that a 1 °C increase in maximum temperature (T_max) resulted in a 1.6% (95% CI: 1.0%-2.2%) increase in HFRS; a 1 mm increase in weekly precipitation was associated with 0.2% (95%CI: 0.1%-0.3%) increase in HFRS; a 1% increase in average relative humidity was associated with a 0.9% (95%CI: 0.5%-1.2%) increase in HFRS. The lags with the largest effects for T_max, precipitation, and relative humidity occurred in weeks 29, 22, and 16, respectively. Lagged effects of meteorological factors did not end after an epidemic season but waned gradually in the following 3-4 epidemic seasons. Weather variability plays a significant role in HFRS transmission in China. The long duration of lagged effects indicates the necessity of continuous interventions following the epidemics.

Protein kinase A phosphorylates the Nem1-Spo7 protein phosphatase complex that regulates the phosphorylation state of the phosphatidate phosphatase Pah1 in yeast

The Nem1-Spo7 protein phosphatase plays a role in lipid synthesis by controlling the membrane localization of Pah1, the diacylglycerol-producing phosphatidate (PA) phosphatase that is crucial for the synthesis of triacylglycerol in the yeast Saccharomyces cerevisiae By dephosphorylating Pah1, Nem1-Spo7 facilitates its translocation to the nuclear/endoplasmic reticulum membrane for catalytic activity. Like its substrate Pah1, Nem1-Spo7 is phosphorylated in the cell, but the specific protein kinases involved remain to be identified. In this study, we demonstrate that the Nem1-Spo7 complex is phosphorylated by protein kinase A (PKA), which is associated with active cell growth, metabolic activity, and membrane phospholipid synthesis. In vitro phosphorylation of purified Nem1-Spo7 and of their synthetic peptides revealed that both subunits of the phosphatase complex are PKA substrates. Using phosphoamino acid and phosphopeptide-mapping analyses coupled with site-directed mutagenesis, we identified Ser-140 and Ser-210 of Nem1 and Ser-28 of Spo7 as PKA-targeted phosphorylation sites. Immunodetection of the phosphatase complex from the cell with anti-PKA substrate antibody confirmed the in vivo phosphorylations of Nem1 and Spo7 on the serine residues. Lipid-labeling analysis of cells bearing phosphorylation-deficient alleles of NEM1 and SPO7 indicated that the PKA phosphorylation of the phosphatase complex stimulates phospholipid synthesis and attenuates the synthesis of triacylglycerol. This work advances the understanding of how PKA-mediated posttranslational modifications of Nem1 and Spo7 regulate lipid synthesis in yeast.

China's capacity of hospitals to deal with infectious diseases in the context of climate change

OBJECTIVES

Infectious diseases are a major cause of morbidity and mortality in China. The capacity of hospitals to deal with the challenge from emerging and re-emerging infectious diseases due to climate change is of great importance to population health. This study aimed to explore the capacity of hospitals in China to deal with such challenges.

METHODS

A cross-sectional questionnaire survey was utilized to gauge information regarding capacity of hospitals to deal with infectious diseases in the context of climate change among 611 clinical professionals whose roles pertained to infectious disease diagnosis, treatment and management in Anhui Province of China. Descriptive analysis and logistic regression analysis were performed on the data.

RESULTS

More than 90% of participants believed climate change would have an adverse influence on population health and infectious disease control in China. Most indicated that their hospitals were well prepared for emerging infectious diseases at present, and they considered that logistical support in hospitals (e.g. administrative and maintenance services) should be strengthened for future capacity building. The majority of participants suggested that effective prevention and control measures, more interdisciplinary collaborations, more funding in rural areas for health care, and improved access to facilities enabling online reporting of infectious diseases, were extremely important strategies in building capacity to curb the population health impact of emerging and re-emerging infectious diseases due to climate change in China.

CONCLUSIONS

Clinical professionals recognized that climate change will likely increase the transmission of infectious diseases. Although rural health care and hospitals' logistical support need to be improved, most professionals believed their hospitals to be capable of dealing with emerging diseases. They thought that interdisciplinary and cross-regional collaborations, together with necessary resource support (e.g. improved facilities for rural health care) would be important control strategies.

Host Pah1p phosphatidate phosphatase limits viral replication by regulating phospholipid synthesis

Replication of positive-strand RNA viruses [(+)RNA viruses] takes place in membrane-bound viral replication complexes (VRCs). Formation of VRCs requires virus-mediated manipulation of cellular lipid synthesis. Here, we report significantly enhanced brome mosaic virus (BMV) replication and much improved cell growth in yeast cells lacking PAH1 (pah1Δ), the sole yeast ortholog of human LIPIN genes. PAH1 encodes Pah1p (phosphatidic acid phosphohydrolase), which converts phosphatidate (PA) to diacylglycerol that is subsequently used for the synthesis of the storage lipid triacylglycerol. Inactivation of Pah1p leads to altered lipid composition, including high levels of PA, total phospholipids, ergosterol ester, and free fatty acids, as well as expansion of the nuclear membrane. In pah1Δ cells, BMV replication protein 1a and double-stranded RNA localized to the extended nuclear membrane, there was a significant increase in the number of VRCs formed, and BMV genomic replication increased by 2-fold compared to wild-type cells. In another yeast mutant that lacks both PAH1 and DGK1 (encodes diacylglycerol kinase converting diacylglycerol to PA), which has a normal nuclear membrane but maintains similar lipid compositional changes as in pah1Δ cells, BMV replicated as efficiently as in pah1Δ cells, suggesting that the altered lipid composition was responsible for the enhanced BMV replication. We further showed that increased levels of total phospholipids play an important role because the enhanced BMV replication required active synthesis of phosphatidylcholine, the major membrane phospholipid. Moreover, overexpression of a phosphatidylcholine synthesis gene (CHO2) promoted BMV replication. Conversely, overexpression of PAH1 or plant PAH1 orthologs inhibited BMV replication in yeast or Nicotiana benthamiana plants. Competing with its host for limited resources, BMV inhibited host growth, which was markedly alleviated in pah1Δ cells. Our work suggests that Pah1p promotes storage lipid synthesis and thus represses phospholipid synthesis, which in turn restricts both viral replication and cell growth during viral infection.

Fat storage-inducing transmembrane (FIT or FITM) proteins are related to lipid phosphatase/phosphotransferase enzymes

Fat storage-inducing transmembrane (FIT or FITM) proteins have been implicated in the partitioning of triacylglycerol to lipid droplets and the budding of lipid droplets from the ER. At the molecular level, the sole relevant interaction is that FITMs directly bind to triacyglycerol and diacylglycerol, but how they function at the molecular level is not known. Saccharomyces cerevisiae has two FITM homologues: Scs3p and Yft2p. Scs3p was initially identified because deletion leads to inositol auxotrophy, with an unusual sensitivity to addition of choline. This strongly suggests a role for Scs3p in phospholipid biosynthesis. Looking at the FITM family as widely as possible, we found that FITMs are widespread throughout eukaryotes, indicating presence in the last eukaryotic common ancestor. Protein alignments also showed that FITM sequences contain the active site of lipid phosphatase/phosphotransferase (LPT) enzymes. This large family transfers phosphate-containing headgroups either between lipids or in exchange for water. We confirmed the prediction that FITMs are related to LPTs by showing that single amino-acid substitutions in the presumptive catalytic site prevented their ability to rescue growth of the mutants on low inositol/high choline media when over-expressed. The substitutions also prevented rescue of other phenotypes associated with loss of FITM in yeast, including mistargeting of Opi1p, defective ER morphology, and aberrant lipid droplet budding. These results suggest that Scs3p, Yft2p and FITMs in general are LPT enzymes involved in an as yet unknown critical step in phospholipid metabolism.

A conserved tryptophan within the WRDPLVDID domain of yeast Pah1 phosphatidate phosphatase is required for its in vivo function in lipid metabolism

PAH1-encoded phosphatidate phosphatase, which catalyzes the dephosphorylation of phosphatidate to produce diacylglycerol at the endoplasmic reticulum membrane, plays a major role in controlling the utilization of phosphatidate for the synthesis of triacylglycerol or membrane phospholipids. The conserved N-LIP and haloacid dehalogenase-like domains of Pah1 are required for phosphatidate phosphatase activity and the in vivo function of the enzyme. Its non-conserved regions, which are located between the conserved domains and at the C terminus, contain sites for phosphorylation by multiple protein kinases. Truncation analyses of the non-conserved regions showed that they are not essential for the catalytic activity of Pah1 and its physiological functions (e.g. triacylglycerol synthesis). This analysis also revealed that the C-terminal region contains a previously unrecognized WRDPLVDID domain (residues 637-645) that is conserved in yeast, mice, and humans. The deletion of this domain had no effect on the catalytic activity of Pah1 but caused the loss of its in vivo function. Site-specific mutational analyses of the conserved residues within WRDPLVDID indicated that Trp-637 plays a crucial role in Pah1 function. This work also demonstrated that the catalytic activity of Pah1 is required but is not sufficient for its in vivo functions.

Phosphatidate phosphatase regulates membrane phospholipid synthesis via phosphatidylserine synthase

The yeast Saccharomyces cerevisiae serves as a model eukaryote to elucidate the regulation of lipid metabolism. In exponentially growing yeast, a diverse set of membrane lipids are synthesized from the precursor phosphatidate via the liponucleotide intermediate CDP-diacylglycerol. As cells exhaust nutrients and progress into the stationary phase, phosphatidate is channeled via diacylglycerol to the synthesis of triacylglycerol. The CHO1-encoded phosphatidylserine synthase, which catalyzes the committed step in membrane phospholipid synthesis via CDP-diacylglycerol, and the PAH1-encoded phosphatidate phosphatase, which catalyzes the committed step in triacylglycerol synthesis are regulated throughout cell growth by genetic and biochemical mechanisms to control the balanced synthesis of membrane phospholipids and triacylglycerol. The loss of phosphatidate phosphatase activity (e.g., pah1Δ mutation) increases the level of phosphatidate and its conversion to membrane phospholipids by inducing Cho1 expression and phosphatidylserine synthase activity. The regulation of the CHO1 expression is mediated through the inositol-sensitive upstream activation sequence (UAS_INO), a cis-acting element for the phosphatidate-controlled Henry (Ino2-Ino4/Opi1) regulatory circuit. Consequently, phosphatidate phosphatase activity regulates phospholipid synthesis through the transcriptional regulation of the phosphatidylserine synthase enzyme.

Men's weight loss stories: How personal confession, responsibility and transformation work as social control

Obesity is considered a public health concern. In Australia, there are a greater number of overweight or obese men compared with women. The media is an important source of information about body weight and weight management. We undertook a qualitative study to analyse men's weight loss stories in a popular men's magazine. Between January 2009 and December 2012, we collected 47 men's weight loss stories from the Australian edition of Men's Health magazine. We undertook thematic analysis to examine the stories. Confession, personal responsibility, appearance and transformation were key themes. The stories describe the men's self-discipline and their monitoring and tracking of their behaviours as activities which supported their weight loss. In this way, the stories promote the importance of such panoptic self-surveillance and self-discipline to the readers. We consider how such stories contribute to the wider synoptic system of media messages about body weight.

Yeast PAH1-encoded phosphatidate phosphatase controls the expression of CHO1-encoded phosphatidylserine synthase for membrane phospholipid synthesis

The PAH1-encoded phosphatidate phosphatase (PAP), which catalyzes the committed step for the synthesis of triacylglycerol in Saccharomyces cerevisiae, exerts a negative regulatory effect on the level of phosphatidate used for the de novo synthesis of membrane phospholipids. This raises the question whether PAP thereby affects the expression and activity of enzymes involved in phospholipid synthesis. Here, we examined the PAP-mediated regulation of CHO1-encoded phosphatidylserine synthase (PSS), which catalyzes the committed step for the synthesis of major phospholipids via the CDP-diacylglycerol pathway. The lack of PAP in the pah1Δ mutant highly elevated PSS activity, exhibiting a growth-dependent up-regulation from the exponential to the stationary phase of growth. Immunoblot analysis showed that the elevation of PSS activity results from an increase in the level of the enzyme encoded by CHO1 Truncation analysis and site-directed mutagenesis of the CHO1 promoter indicated that Cho1 expression in the pah1Δ mutant is induced through the inositol-sensitive upstream activation sequence (UAS_INO), a cis-acting element for the phosphatidate-controlled Henry (Ino2-Ino4/Opi1) regulatory circuit. The abrogation of Cho1 induction and PSS activity by a CHO1 UAS_INO mutation suppressed pah1Δ effects on lipid synthesis, nuclear/endoplasmic reticulum membrane morphology, and lipid droplet formation, but not on growth at elevated temperature. Loss of the DGK1-encoded diacylglycerol kinase, which converts diacylglycerol to phosphatidate, partially suppressed the pah1Δ-mediated induction of Cho1 and PSS activity. Collectively, these data showed that PAP activity controls the expression of PSS for membrane phospholipid synthesis.

Perceptions of malaria control and prevention in an era of climate change: a cross-sectional survey among CDC staff in China

BACKGROUND

Though there was the significant decrease in the incidence of malaria in central and southwest China during the 1980s and 1990s, there has been a re-emergence of malaria since 2000.

METHODS

A cross-sectional survey was conducted amongst the staff of eleven Centers for Disease Control and Prevention (CDC) in China to gauge their perceptions regarding the impacts of climate change on malaria transmission and its control and prevention. Descriptive analysis was performed to study CDC staff's knowledge, attitudes, perceptions and suggestions for malaria control in the face of climate change.

RESULTS

A majority (79.8%) of CDC staff were concerned about climate change and 79.7% believed the weather was becoming warmer. Most participants (90.3%) indicated climate change had a negative effect on population health, 92.6 and 86.8% considered that increasing temperatures and precipitation would influence the transmission of vector-borne diseases including malaria. About half (50.9%) of the surveyed staff indicated malaria had re-emerged in recent years, and some outbreaks were occurring in new geographic areas. The main reasons for such re-emergence were perceived to be: mosquitoes in high-density, numerous imported cases, climate change, poor environmental conditions, internal migrant populations, and lack of health awareness.

CONCLUSIONS

This study found most CDC staff endorsed the statement that climate change had a negative impact on infectious disease transmission. Malaria had re-emerged in some areas of China, and most of the staff believed that this can be managed. However, high densities of mosquitoes and the continuous increase in imported cases of malaria in local areas, together with environmental changes are bringing about critical challenges to malaria control in China. This study contributes to an understanding of climate change related perceptions of malaria control and prevention amongst CDC staff. It may help to formulate in-house training guidelines, community health promotion programmes and policies to improve the capacity of malaria control and prevention in the face of climate change in China.

Tips on the analysis of phosphatidic acid by the fluorometric coupled enzyme assay

The fluorometric coupled enzyme assay to measure phosphatidic acid (PA) involves the solubilization of extracted lipids in Triton X-100, deacylation, and the oxidation of PA-derived glycerol-3-phosphate to produce hydrogen peroxide for conversion of Amplex Red to resorufin. The enzyme assay is sensitive, but plagued by high background fluorescence from the peroxide-containing detergent and incomplete heat inactivation of lipoprotein lipase. These problems affecting the assay reproducibility were obviated by the use of highly pure Triton X-100 and by sufficient heat inactivation of the lipase enzyme. The enzyme assay could accurately measure the PA content from the subcellular fractions of yeast cells.

[CT typing and surgical approach for adenocarcinoma of the esophagogastric junction]

Objective: To investigate the feasibility, safety and efficacy of preoperative CT in the classification of adenocarcinoma of the esophagogastric junction. Methods: A total of 517 consecutive patients from May 2012 to June 2016 with esophagogastric junction carcinoma in the department of general surgery of Henan Cancer Hospital was retrospectively analyzed, according to the clinical pathological data of three type four layer method and statistics of various types of surgery in patients with preoperative enhanced CT. Results: 517 patients were successfully received surgery, including 152 cases of type Ⅰ(131 cases of complete abdominal surgery, 21 cases of abdominal incision diaphragm in thoracic surgery), 239 cases of type Ⅱ (177 cases of complete abdominal surgery, 62 cases of abdominal incision diaphragm in thoracic surgery), Ⅲ/Ⅳ type choice of chest abdominal surgery in 126 cases. The operation time was (102±17) min, the amount of hemorrhage was (136±18) ml, the dominant anastomotic fistula happened in 16 cases, 5 cases of pancreatic fistula, 7 cases of intestinal obstruction, anastomotic stenosis in 3 cases, thoracic and abdominal sensation in 12 cases, all the complications were cured by conservative treatment. The average value of esophageal resection margin was(5.1±0.6)cm, 2 cases with positive residual tumor margin and average length of stay was (8.9±1.6)d. Conclusion: Using preoperative enhanced CT in the adenocarcinoma of the esophagogastric junction to choose surgical approach can ensure the safety margin. What's more, unnecessary thoracotomy is reduced which is expected to be a new classification method for the operation of esophagogastric junction cancer.

[The advantage of artery approach in lymph node sorting of rectal cancer]

Objective: To explore the technical advantages of artery approach in lymph node sortingofrectal cancer. Methods: Sixty patients with rectal cancer who treated in general surgery department of Henan provincial tumor hospitalfrom July 2015 to January 2016 were enrolled. Patientswere divided into two groupsrandomly.Lymph node sorting methods of control group andobservation group were the traditional method and the artery approach method respectively. The total number of lymph nodes, the average inspection number, the patients number of lymph nodes less than 12, the number of positive lymph nodes, the metastasis rate of the patients, the number of average diameter less than 5 mm, the number of the positive lymph nodes which average diameter less than 5 mm, the sorting time of lymph nodes, the total number of every stationand other indicators were collected and compared. Results: There wasa significant difference between the observation group and the control groupin the total number(553 vs 395, P<0.05), the number of positive ones(96 vs 54, P<0.05), average inspection number(18.43±5.93 vs 13.27±1.96, P=0.000), the sorting time (min) (14.1±2.5 vs 17.4±3.2, P=0.000), the average diameter less than 5 mm number(4.73±1.31 vs 1.23±1.14, P=0.000), the number of positive ones average diameter less than 5 mm(0.97±1.03 vs 0.20±0.55, P=0.010), the first(8.17±4.58 vs 5.07±1.96, P=0.000) and second station(6.57±1.87 vs 4.90±1.69, P=0.001)inspection number.The inspection number less than 12, the positive rate of lymph node, the metastatic rate of the patient and the inspection number of third station have no significant differences (all P≥0.05). Conclusion: Theartery approach method inrectal cancer lymph node inspectionhas many advantages such as simple operation, obtaining more lymph nodes and more accurate pathological staging.

Phosphorylation of lipid metabolic enzymes by yeast protein kinase C requires phosphatidylserine and diacylglycerol

Protein kinase C in Saccharomyces cerevisiae, i.e., Pkc1, is an enzyme that plays an important role in signal transduction and the regulation of lipid metabolic enzymes. Pkc1 is structurally similar to its counterparts in higher eukaryotes, but its requirement of phosphatidylserine (PS) and diacylglycerol (DAG) for catalytic activity has been unclear. In this work, we examined the role of these lipids in Pkc1 activity with protein and peptide substrates. In agreement with previous findings, yeast Pkc1 did not require PS and DAG for its activity on the peptide substrates derived from lipid metabolic proteins such as Pah1 [phosphatidate (PA) phosphatase], Nem1 (PA phosphatase phosphatase), and Spo7 (protein phosphatase regulatory subunit). However, the lipids were required for Pkc1 activity on the protein substrates Pah1, Nem1, and Spo7. Compared with DAG, PS had a greater effect on Pkc1 activity, and its dose-dependent interaction with the protein kinase was shown by the liposome binding assay. The Pkc1-mediated degradation of Pah1 was attenuated in the cho1Δ mutant, which is deficient in PS synthase, supporting the notion that the phospholipid regulates Pkc1 activity in vivo.

Association between dengue fever incidence and meteorological factors in Guangzhou, China, 2005-2014

This study aims to (1) investigate the associations between climatic factors and dengue; and (2) identify the susceptible subgroups. De-identified daily dengue cases in Guangzhou for 2005-2014 were obtained from the Chinese Center for Disease Control and Prevention. Weather data were downloaded from the China Meteorological Data Sharing Service System. Distributed lag non-linear models (DLNM) were used to graphically demonstrate the three-dimensional temperature-dengue association. Generalised estimating equation models (GEE) with piecewise linear spline functions were used to quantify the temperature-dengue associations. Threshold values were estimated using a broken-stick model. Middle-aged and older people, people undertaking household duties, retirees, and those unemployed were at high risk of dengue. Reversed U-shaped non-linear associations were found between ambient temperature, relative humidity, extreme wind velocity, and dengue. The optimal maximum temperature (T_max) range for dengue transmission in Guangzhou was 21.6-32.9°C, and 11.2-23.7°C for minimum temperature (T_min). A 1°C increase of T_max and T_min within these ranges was associated with 11.9% and 9.9% increase in dengue at lag0, respectively. Although lag effects of temperature were observed for up to 141 days for T_max and 150 days for T_min, the maximum lag effects were observed at 32 days and 39 days respectively. Average relative humidity was negatively associated with dengue when it exceeded 78.9%. Maximum wind velocity (>10.7m/s) inhibited dengue transmission. Climatic factors had significant impacts on dengue in Guangzhou. Lag effects of temperature on dengue lasted the local whole epidemic season. To reduce the likely increasing dengue burden, more efforts are needed to strengthen the capacity building of public health systems.

Phosphorylation of Dgk1 Diacylglycerol Kinase by Casein Kinase II Regulates Phosphatidic Acid Production in Saccharomyces cerevisiae

In the yeast Saccharomyces cerevisiae, Dgk1 diacylglycerol (DAG) kinase catalyzes the CTP-dependent phosphorylation of DAG to form phosphatidic acid (PA). The enzyme in conjunction with Pah1 PA phosphatase controls the levels of PA and DAG for the synthesis of triacylglycerol and membrane phospholipids, the growth of the nuclear/endoplasmic reticulum membrane, and the formation of lipid droplets. Little is known about how DAG kinase activity is regulated by posttranslational modification. In this work, we examined the phosphorylation of Dgk1 DAG kinase by casein kinase II (CKII). When phosphate groups were globally reduced using nonspecific alkaline phosphatase, Triton X-100-solubilized membranes from DGK1-overexpressing cells showed a 7.7-fold reduction in DAG kinase activity; the reduced enzyme activity could be increased 5.5-fold by treatment with CKII. Dgk1(1-77) expressed heterologously in Escherichia coli was phosphorylated by CKII on a serine residue, and its phosphorylation was dependent on time as well as on the concentrations of CKII, ATP, and Dgk1(1-77). We used site-specific mutagenesis, coupled with phosphorylation analysis and phosphopeptide mapping, to identify Ser-45 and Ser-46 of Dgk1 as the CKII target sites, with Ser-46 being the major phosphorylation site. In vivo, the S46A and S45A/S46A mutations of Dgk1 abolished the stationary phase-dependent stimulation of DAG kinase activity. In addition, the phosphorylation-deficient mutations decreased Dgk1 function in PA production and in eliciting pah1Δ phenotypes, such as the expansion of the nuclear/endoplasmic reticulum membrane, reduced lipid droplet formation, and temperature sensitivity. This work demonstrates that the CKII-mediated phosphorylation of Dgk1 regulates its function in the production of PA.

Advanced remediation of uranium-contaminated soil

The existing decontamination method using electrokinetic equipment after acidic washing for uranium-contaminated soil requires a long decontamination time and a significant amount of electric power. However, after soil washing, with a sulfuric acid solution and an oxidant at 65 °C, the removal of the muddy solution using a 100 mesh sieve can decrease the radioactivity of the remaining coarse soil to the clearance level. Therefore, only a small amount of fine soil collected from the muddy solution requires the electrokinetic process for its decontamination. Furthermore, it is found that the selective removal of uranium from the sulfuric washing solution is not obtained using an anion exchanger but rather using a cation exchanger, unexpectedly. More than 90% of the uranium in the soil washing solutions is adsorbed on the S-950 resin, and 87% of the uranium adsorbed on S-950 is desorbed by washing with a 0.5 M Na₂CO₃ solution at 60 °C.

Redundant roles of the phosphatidate phosphatase family in triacylglycerol synthesis in human adipocytes

AIMS/HYPOTHESIS

In mammals, the evolutionary conserved family of Mg(2+)-dependent phosphatidate phosphatases (PAP1), involved in phospholipid and triacylglycerol synthesis, consists of lipin-1, lipin-2 and lipin-3. While mutations in the murine Lpin1 gene cause lipodystrophy and its knockdown in mouse 3T3-L1 cells impairs adipogenesis, deleterious mutations of human LPIN1 do not affect adipose tissue distribution. However, reduced LPIN1 and PAP1 activity has been described in participants with type 2 diabetes. We aimed to characterise the roles of all lipin family members in human adipose tissue and adipogenesis.

METHODS

The expression of the lipin family was analysed in adipose tissue in a cross-sectional study. Moreover, the effects of lipin small interfering RNA (siRNA)-mediated depletion on in vitro human adipogenesis were assessed.

RESULTS

Adipose tissue gene expression of the lipin family is altered in type 2 diabetes. Depletion of every lipin family member in a human Simpson-Golabi-Behmel syndrome (SGBS) pre-adipocyte cell line, alters expression levels of adipogenic transcription factors and lipid biosynthesis genes in early stages of differentiation. Lipin-1 knockdown alone causes a 95% depletion of PAP1 activity. Despite the reduced PAP1 activity and alterations in early adipogenesis, lipin-silenced cells differentiate and accumulate neutral lipids. Even combinatorial knockdown of lipins shows mild effects on triacylglycerol accumulation in mature adipocytes.

CONCLUSIONS/INTERPRETATION

Overall, our data support the hypothesis of alternative pathways for triacylglycerol synthesis in human adipocytes under conditions of repressed lipin expression. We propose that induction of alternative lipid phosphate phosphatases, along with the inhibition of lipid hydrolysis, contributes to the maintenance of triacylglycerol content to near normal levels.

[Treatment of advanced Siewert type Ⅱ esophagogastric junction adenocarcinoma by thoracoabdominal radical gastrectomy and D2 lymphadenectomy]

OBJECTIVE

To investigate the advantages of thoracoabdominal radical gastrectomy for advanced Siewert type Ⅱ adenocarcinoma of the esophagogastric junction.

METHODS

Clinical data of 86 patients with Siewert type Ⅱ adennocarcinoma of the esophagogastric junction who received surgical treatment at the Henan Provincial Tumor Hospital from January 2015 to January 2016 were retrospectively analyzed. Among them, 44 patients underwent abdominal operation (abdominal group), and 42 patients underwent thoracoabdominal radical gastrectomy (thoraco-abdominal group). The operation time, lymph node number, distance between the tumor and cutting edge, amount of intraoperational blood loss, postoperative pulmonary complications, and postoperative hospital stay in the two groups were compared.

RESULTS

Comparing the thoracoabdominal group with the abdominal group, the number of removed lymph nodes was 41.57±9.22 vs. 35.09±10.61 (P<0.01), the number of removed mediastinal lymph nodes was 6.38±1.50 vs. 3.52±1.42 (P<0.01), the distance between the tumor and cut edge was (5.62±0.73) cm vs. (3.30±0.85) cm (P<0.01), whereas the operation time, intraoperative blood loss, postoperative pulmonary complications, occurrence of anastomotic leakage and hospital stay were statistically not significantly different (P>0.05 for all).

CONCLUSIONS

For patients with advanced Siewert type Ⅱ adenocarcinoma of the esophagogastric junction, radical gastrectomy through thoracoabdominal approach can resect a longer segment of the esophagus, dissect more mediastinal lymph nodes, and does not increase post-operative complications and extend hospital stay, thus, exhibits obvious advantages in the surgical treatment of Siewert Ⅱ adenocarcinoma of the esophagogastric junction.

Perceptions of capacity for infectious disease control and prevention to meet the challenges of dengue fever in the face of climate change: A survey among CDC staff in Guangdong Province, China

BACKGROUND

Dengue fever is an important climate-sensitive mosquito-borne viral disease that poses a risk to half the world's population. The disease is a major public health issue in China where in 2014 a major outbreak occurred in Guangdong Province. This study aims to gauge health professionals' perceptions about the capacity of infectious disease control and prevention to meet the challenge of dengue fever in the face of climate change in Guangdong Province, China.

METHODS

A cross-sectional questionnaire survey was administered among staff in the Centers for Disease Control and Prevention (CDCs) in Guangdong Province. Data analysis was undertaken using descriptive methods and logistic regression.

RESULTS

In total, 260 questionnaires were completed. Most participants (80.7%) thought climate change would have a negative effect on population health, and 98.4% of participants reported dengue fever had emerged or re-emerged in China in recent years. Additionally, 74.9% of them indicated that the capability of the CDCs to detect infectious disease outbreak/epidemic at an early stage was excellent; 86.3% indicated laboratories could provide diagnostic support rapidly; and 83.1% believed levels of current staff would be adequate in the event of a major outbreak. Logistic regression analysis showed higher levels of CDCs were perceived to have better capacity for infectious disease control and prevention. Only 26.8% of participants thought they had a good understanding of climate change, and most (85.4%) thought they needed more information about the health impacts of climate change. Most surveyed staff suggested the following strategies to curb the public health impact of infectious diseases in relation to climate change: primary prevention measures, strengthening the monitoring of infectious diseases, the ability to actively forecast disease outbreaks by early warning systems, and more funding for public health education programs.

CONCLUSION

Vigilant disease and vector surveillance, preventive practice and health promotion programs will likely be significant in addressing the threat of dengue fever in the future. Further efforts are needed to strengthen the awareness of climate change among health professionals, and to promote relevant actions to minimize the health burden of infectious diseases in a changing climate. Results will be critical for policy makers facing the current and future challenges associated with infectious disease prevention and control in China.

Phosphorylation of Yeast Pah1 Phosphatidate Phosphatase by Casein Kinase II Regulates Its Function in Lipid Metabolism

Pah1 phosphatidate phosphatase in Saccharomyces cerevisiae catalyzes the penultimate step in the synthesis of triacylglycerol (i.e. the production of diacylglycerol by dephosphorylation of phosphatidate). The enzyme playing a major role in lipid metabolism is subject to phosphorylation (e.g. by Pho85-Pho80, Cdc28-cyclin B, and protein kinases A and C) and dephosphorylation (e.g. by Nem1-Spo7) that regulate its cellular location, catalytic activity, and stability/degradation. In this work, we show that Pah1 is a substrate for casein kinase II (CKII); its phosphorylation was time- and dose-dependent and was dependent on the concentrations of Pah1 (Km = 0.23 μm) and ATP (Km = 5.5 μm). By mass spectrometry, truncation analysis, site-directed mutagenesis, phosphopeptide mapping, and phosphoamino acid analysis, we identified that >90% of its phosphorylation occurs on Thr-170, Ser-250, Ser-313, Ser-705, Ser-814, and Ser-818. The CKII-phosphorylated Pah1 was a substrate for the Nem1-Spo7 protein phosphatase and was degraded by the 20S proteasome. The prephosphorylation of Pah1 by protein kinase A or protein kinase C reduced its subsequent phosphorylation by CKII. The prephosphorylation of Pah1 by CKII reduced its subsequent phosphorylation by protein kinase A but not by protein kinase C. The expression of Pah1 with combined mutations of S705D and 7A, which mimic its phosphorylation by CKII and lack of phosphorylation by Pho85-Pho80, caused an increase in triacylglycerol content and lipid droplet number in cells expressing the Nem1-Spo7 phosphatase complex.

The brown adipocyte protein CIDEA promotes lipid droplet fusion via a phosphatidic acid-binding amphipathic helix

Maintenance of energy homeostasis depends on the highly regulated storage and release of triacylglycerol primarily in adipose tissue, and excessive storage is a feature of common metabolic disorders. CIDEA is a lipid droplet (LD)-protein enriched in brown adipocytes promoting the enlargement of LDs, which are dynamic, ubiquitous organelles specialized for storing neutral lipids. We demonstrate an essential role in this process for an amphipathic helix in CIDEA, which facilitates embedding in the LD phospholipid monolayer and binds phosphatidic acid (PA). LD pairs are docked by CIDEA trans-complexes through contributions of the N-terminal domain and a C-terminal dimerization region. These complexes, enriched at the LD–LD contact site, interact with the cone-shaped phospholipid PA and likely increase phospholipid barrier permeability, promoting LD fusion by transference of lipids. This physiological process is essential in adipocyte differentiation as well as serving to facilitate the tight coupling of lipolysis and lipogenesis in activated brown fat.

DOI:http://dx.doi.org/10.7554/eLife.07485.001

If other energy sources become unavailable, cells fall back on stores of fatty molecules called lipids. These are held in membrane-enclosed compartments in the cell called lipid droplets, which in mammals are particularly abundant in fat cells called adipocytes. There are two main types of adipocytes: white adipocytes have a single giant lipid droplet, whereas brown adipocytes contain many smaller droplets.

Proteins embedded in the membrane that surrounds a lipid droplet help to control the droplet’s growth and when it releases lipids. For example, a protein called CIDEA, which is only found in brown adipocytes, helps lipid droplets to grow by enabling one droplet to transfer its contents to another droplet. However, little is known about how this occurs.

By combining cell biology, biophysical and computer modelling approaches, Barneda et al. investigated how normal and mutant forms of CIDEA affect the growth of lipid droplets. These experiments identified a helix in the structure of CIDEA that embeds it in the membrane, from where it can then interact with CIDEA proteins on other lipid droplets to hold the droplets together. In addition, the helix interacts with a molecule in the lipid droplet membrane called phosphatidic acid. Barneda et al. suggest that this interaction helps to transfer the contents of one droplet to another by making it easier for lipids to move through the droplets’ membranes.

The next challenge is to characterize the mechanisms that control CIDEA activity to influence the formation of the multiple lipid droplets that distinguish brown and BRITE (brown-in-white) adipocytes from white adipocytes. The lipid droplets in brown adipocytes are an important target for research to combat obesity, due to the 'burning' rather than storing of lipids that occurs in these cells.

DOI:http://dx.doi.org/10.7554/eLife.07485.002

Infectious Diseases, Urbanization and Climate Change: Challenges in Future China

China is one of the largest countries in the world with nearly 20% of the world's population. There have been significant improvements in economy, education and technology over the last three decades. Due to substantial investments from all levels of government, the public health system in China has been improved since the 2003 severe acute respiratory syndrome (SARS) outbreak. However, infectious diseases still remain a major population health issue and this may be exacerbated by rapid urbanization and unprecedented impacts of climate change. This commentary aims to explore China's current capacity to manage infectious diseases which impair population health. It discusses the existing disease surveillance system and underscores the critical importance of strengthening the system. It also explores how the growing migrant population, dramatic changes in the natural landscape following rapid urbanization, and changing climatic conditions can contribute to the emergence and re-emergence of infectious disease. Continuing research on infectious diseases, urbanization and climate change may inform the country's capacity to deal with emerging and re-emerging infectious diseases in the future.