The role of the Parkinson's disease gene PARK9 in essential cellular pathways and the manganese homeostasis network in yeast

YPK9 (Yeast PARK9; also known as YOR291W) is a non-essential yeast gene predicted by sequence to encode a transmembrane P-type transport ATPase. However, its substrate specificity is unknown. Mutations in the human homolog of YPK9, ATP13A2/PARK9, have been linked to genetic forms of early onset parkinsonism. We previously described a strong genetic interaction between Ypk9 and another Parkinson's disease (PD) protein α-synuclein in multiple model systems, and a role for Ypk9 in manganese detoxification in yeast. In humans, environmental exposure to toxic levels of manganese causes a syndrome similar to PD and is thus an environmental risk factor for the disease. How manganese contributes to neurodegeneration is poorly understood. Here we describe multiple genome-wide screens in yeast aimed at defining the cellular function of Ypk9 and the mechanisms by which it protects cells from manganese toxicity. In physiological conditions, we found that Ypk9 genetically interacts with essential genes involved in cellular trafficking and the cell cycle. Deletion of Ypk9 sensitizes yeast cells to exposure to excess manganese. Using a library of non-essential gene deletions, we screened for additional genes involved in tolerance to excess manganese exposure, discovering several novel pathways involved in manganese homeostasis. We defined the dependence of the deletion strain phenotypes in the presence of manganese on Ypk9, and found that Ypk9 deletion modifies the manganese tolerance of only a subset of strains. These results confirm a role for Ypk9 in manganese homeostasis and illuminates cellular pathways and biological processes in which Ypk9 likely functions.     

Reliability and validity of simplified Chinese version of Roland-Morris questionnaire in evaluating rural and urban patients with low back pain

Objective

The causes of low back pain in China and Western countries are extremely different. We attempted to analyze the risk factors of low back pain in urban and rural patients under the dual economy with the simplified Chinese version of Roland-Morris disability questionnaire (SC-RMDQ) to demonstrate that SC-RMDQ could evaluate patients with low back pain arising from different causes.

Methods

Roland-Morris disability questionnaire was translated into SCRMDQ according to international guidelines for questionnaire adaptation. In this study, causes of low back pain of 187 outpatients and inpatients (99 urban patients and 88 rural patients) were analyzed. All patients underwent simplified Chinese version of Roland-Morris disability questionnaire (SC-RMDQ), simplified Chinese Oswestry disability index (SCODI) and visual analogue scale (VAS). Reliability was tested using reproducibility (intraclass coefficient of correlation – ICC) and internal consistency (Cronbach''s alpha). Validity was tested using Pearson correlation analysis.

Results

The leading causes for low back pain were sedentariness (38.4%) and vibration (18.1%) in urban patients and waist bending (48.9%) and spraining (25%) in rural patients. Although causes of low back pain in the two groups of population were completely different, SCRMDQ had high internal consistency (Cronbach''s α value of 0.874 in urban patients and 0.883 in rural patients) and good reproducibility (ICC value of .952 in urban patients and 0.949 in rural patients, P<0.01). SCRMDQ also showed significant correlation with Simplified Chinese version of Oswestry disability index (SCODI) and visual analogue scale (VAS) in rural areas (SCRMDQ-SCODI r = 0.841; SCRMDQ -VAS: r = 0.685, P<0.01) and in urban areas (SCRMDQ-SCODI: r = 0.818, P<0.01; SCRMDQ –VAS: r = 0.666, P<0.01).

Conclusions

Although causes of low back pain are completely different in rural and urban patients, SCRMDQ has a good reliability and validity, which is a reliable clinical method to evaluate disability of rural and urban patients.     

Mycobacterium tuberculosis Rv3586 (DacA) is a diadenylate cyclase that converts ATP or ADP into c-di-AMP

Cyclic diguanosine monophosphate (c-di-GMP) and cyclic diadenosine monophosphate (c-di-AMP) are recently identified signaling molecules. c-di-GMP has been shown to play important roles in bacterial pathogenesis, whereas information about c-di-AMP remains very limited. Mycobacterium tuberculosis Rv3586 (DacA), which is an ortholog of Bacillus subtilis DisA, is a putative diadenylate cyclase. In this study, we determined the enzymatic activity of DacA in vitro using high-performance liquid chromatography (HPLC), mass spectrometry (MS) and thin layer chromatography (TLC). Our results showed that DacA was mainly a diadenylate cyclase, which resembles DisA. In addition, DacA also exhibited residual ATPase and ADPase in vitro. Among the potential substrates tested, DacA was able to utilize both ATP and ADP, but not AMP, pApA, c-di-AMP or GTP. By using gel filtration and analytical ultracentrifugation, we further demonstrated that DacA existed as an octamer, with the N-terminal domain contributing to tetramerization and the C-terminal domain providing additional dimerization. Both the N-terminal and the C-terminal domains were essential for the DacA's enzymatically active conformation. The diadenylate cyclase activity of DacA was dependent on divalent metal ions such as Mg(2+), Mn(2+) or Co(2+). DacA was more active at a basic pH rather than at an acidic pH. The conserved RHR motif in DacA was essential for interacting with ATP, and mutation of this motif to AAA completely abolished DacA's diadenylate cyclase activity. These results provide the molecular basis for designating DacA as a diadenylate cyclase. Our future studies will explore the biological function of this enzyme in M. tuberculosis.     

Comparative geno-plasticity analysis of Mycoplasma bovis HB0801 (Chinese isolate)

Mycoplasma bovis pneumonia in cattle has been epidemic in China since 2008. To investigate M. bovis pathogenesis, we completed genome sequencing of strain HB0801 isolated from a lesioned bovine lung from Hubei, China. The genomic plasticity was determined by comparing HB0801 with M. bovis strain ATCC? 25523?/PG45 from cow mastitis milk, Chinese strain Hubei-1 from lesioned lung tissue, and 16 other Mycoplasmas species. Compared to PG45, the genome size of HB0801 was reduced by 11.7 kb. Furthermore, a large chromosome inversion (580 kb) was confirmed in all Chinese isolates including HB0801, HB1007, a strain from cow mastitis milk, and Hubei-1. In addition, the variable surface lipoproteins (vsp) gene cluster existed in HB0801, but contained less than half of the genes, and had poor identity to that in PG45, but they had conserved structures. Further inter-strain comparisons revealed other mechanisms of gene acquisition and loss in HB0801 that primarily involved insertion sequence (IS) elements, integrative conjugative element, restriction and modification systems, and some lipoproteins and transmembrane proteins. Subsequently, PG45 and HB0801 virulence in cattle was compared. Results indicated that both strains were pathogenic to cattle. The scores of gross pathological assessment for the control group, and the PG45- and HB0801-infected groups were 3, 13 and 9, respectively. Meanwhile the scores of lung lesion for these three groups were 36, 70, and 69, respectively. In addition, immunohistochemistry detection demonstrated that both strains were similarly distributed in lungs and lymph nodes. Although PG45 showed slightly higher virulence in calves than HB0801, there was no statistical difference between the strains (P>0.05). Compared to Hubei-1, a total of 122 SNP loci were disclosed in HB0801. In conclusion, although genomic plasticity was thought to be an evolutionary advantage, it did not apparently affect virulence of M. bovis strains in cattle.     

Lysosome-membrane fusion mediated superoxide production in hyperglycaemia-induced endothelial dysfunction

Lysosomal exocytosis and fusion to cellular membrane is critical in the oxidative stress formation of endothelium under apoptotic stimulus. We investigated the role therein of it in hyperglycaemia-induced endothelial dysfunction. The lysosome-membrane fusion was shown by the expression of lamp1, the lysosomal membrane marker, on cellular membrane and the transportation of lysosomal symbolic enzymes into cultural medium. We also examined the ceramide production, lipid rafts (LRs) clustering, colocalization of gp91^phox, a NADPH oxidase subunit (NOX) to LRs clusters, superoxide (O₂ ^{. -}) formation and nitric oxide (NO) content in human umbilical vein endothelial cells (HUVEC) and the endothelium-dependent NO-mediated vasodilation in isolated rat aorta. As compared to normal glucose (5.6 mmol/l, Ctrl) incubation, high glucose (22 mmol/l, HG) exposure facilitated the lysosome-membrane fusion in HUVEC shown by significantly increased quantity of lamp1 protein on cellular membrane and enhanced activity of lysosomal symbolized enzymes in cultural medium. HG incubation also elicited ceramide generation, LRs clustering and gp91^phox colocalization to LRs clusters which were proved to mediate the HG induced O₂ ^{. -} formation and NO depletion in HUVEC. Functionally, the endothelium-dependent NO-mediated vasodilation in aorta was blunted substantially after HG incubation. Moreover, the HG-induced effect including ceramide production, LRs clustering, gp91^phox colocalization to LRs clusters, O₂ ^{. -} formation and endothelial dysfunction could be blocked significantly by the inhibition of lysosome-membrane fusion. We propose that hyperglycaemia-induced endothelial impairment is closely related to the lysosome-membrane fusion and the following LRs clustering, LRs-NOX platforms formation and O₂ ^{. -} production.     

The complete mitochondrial genomes of largemouth bass of the northern subspecies (Micropterus salmoides salmoides) and Florida subspecies (Micropterus salmoides floridanus) and their applications in the identification of largemouth bass species

The largemouth bass belongs to the family Centrarchidae, which includes two subspecies: the northern subspecies, Micropterus salmoides salmoides, and the Florida subspecies, Micropterus salmoides floridanus. In this study, the complete mitochondrial genomes of the two subspecies were sequenced, and their genetic differences were identified. The mitogenomes of M. s. salmoides and M. s. floridanus are 16,486 and 16,479?bp in length, respectively. The two subspecies consisted of 37 genes (13 protein-coding genes, 2 ribosomal RNA, and 22 transfer RNA), which are typical for vertebrate mtDNA. Phylogenetic analysis provided statistical support for the monophyly of the family Centrarchidae. Comparison of the two subspecies' mitogenomes revealed a relatively high number (450) of single nucleotide polymorphisms (SNPs) in protein-coding genes. We characterized SNPs in the partial cytochrome c oxidase subunit 1 gene of different individuals from three cultured populations, one wild northern subspecies population, and one wild Florida subspecies population. Twenty-eight SNPs were fixed with alternative nucleotides in the two subspecies, which could be used for differentiating them. Based on this gene, phylogenetic tree and genetic distance analyses supported that cultured largemouth bass in China belongs to the northern subspecies.     

A novel immobilization method for nuclease P1 on macroporous absorbent resin with glutaraldehyde cross-linking and determination of its properties

Microbial nuclease P₁ from Penicllium citrinum was immobilized on macroporous absorbent resins: strong polar poly (styrene-co-DVB) resin (SPPSD), polymethacrylic ester resin and poly (styrene-co-DVB)-Br resin. The results showed that SPPSD was the best carrier. Three methods of glutaraldehyde cross-linking were used and simultaneous immobilization and cross-linking (CIS) was demonstrated to be the best method. The functional properties of immobilized nuclease P₁ were studied and compared to those of the free enzyme. The highest enzyme activities of free and immobilized nuclease P₁ were obtained in 0.2 M acetate buffer at pH 4.5 and a temperature of 70 °C. An increase in K_m (from 3.165 to 18.125 mg mL^?1) and a decrease in V_max (from 1667.18 to 443.95 U min^?1 mL^?1) were recorded after immobilization. SPPSD-glutaraldehyde-nuclease P₁ exhibited better thermal stability than the free enzyme. The apparent activation energy (E_a) of the free and immobilized nuclease P₁ was 137.04 kJ mol^?1 and 98.43 kJ mol^?1, respectively, implying that the catalytic efficiency of the immobilized enzyme was restricted by mass-transfer rather than kinetic limit.