Biology subjects

Du, P.

Publications and source records attributed to Du, P..

3 recordsLinked to original sources

bioRxiv2018

Sublethal β-lactam antibiotics induce PhpP phosphatase expression and StkP kinase phosphorylation in PBP-independent β-lactam antibiotic resistance of Streptococcus pneumoniae

StkP and PhpP of Streptococcus pneumoniae have been confirmed to compose a signaling couple, in which the former is a serine/threonine (Ser/Thr) kinase while the latter was annotated as a phosphotase. StkP has been reported to be involved in penicillin-binding protein (PBP)-independent penicillin resistance of S. pneumoniae. However, the enzymatic characterization of PhpP and the role of PhpP in StkP-PhpP couple remain poorly understood. Here we showed that 1/4 minimal inhibitory concentration (MIC) of penicillin (PCN) or cefotaxime (CTX), the representatives of {beta}-lactam antibiotics, could induce the expression of stkP and phpP genes and phosphorylation of StkP in PCN/CTX-sensitive strain ATCC6306 and three isolates of S. pneumoniae (MICs: 0.02-0.5 g/ml). The product of phpP gene hydrolyzed PP2C type Ser/Thr phosphotase-specific RRA(pT)VA phosphopeptide substrate with the Km and Kcat values of 277.35 mol/L and 0.71 S-1, and the hydrolytic activity was blocked by sodium fluoride, a PP2C type Ser/Thr phosphatase inhibitor. The phosphorylation levels of StkP in the four phpP gene-knockout ({Delta}phpP) mutants were significantly higher than that in the wild-type strains. In particular, the MICs of PCN and CTX against the {Delta}phpP mutants were significantly elevated as 4-16 g/ml. Therefore, our findings confirmed that sublethal PCN and CTX act as environmental inducers to cause the increase of phpP and stkP gene expression and StkP phosphorylation. PhpP is a PP2C type Ser/Thr protein phosphatase responsible for dephosphorylation of StkP. Knockout of the phpP gene results in a high level of StkP phosphorylation and PBP-independent PCN/CTX resistance of S. pneumoniae.\n\nImportanceStreptococcus pneumoniae is a common pathogen in human populations in many countries and areas due to the prevalence of {beta}-lactam antibiotic-resistant pneumococcal strains. Production of {beta}-lactamases and mutation of penicillin-binding proteins (PBP) have been considered as the major {beta}-lactam antibiotic-resistant mechanisms in bacteria, but S. pneumoniae has not been confirmed to produce any {beta}-lactamases and many pneumococcal strains present PBP mutation-independent {beta}-lactam antibiotic resistance. StkP is a Ser/Thr kinase of S. pneumoniae to compose a signal-couple with PhpP protein. The present study demonstrated that the PhpP is a PP2C-type phosphotase for dephosphorylation of StkP and the sublethal penicillin (PCN) or cefotaxime (CTX) acted as environmental signal molecules to induce the expression of PhpP. The knockout of PhpP-encoding gene caused the PCN/CTX resistance generation of PCN/CTX-sensitive pneumococcal strains. All the data indicate that StkP-PhpP couple of S. pneumoniae is involved in PBP mutation-independent {beta}-lactam antibiotic resistance by phosphorylation of StkP.

microbiology↗

bioRxiv2018

Corilagin controls post-parasiticide schistosome egg-induced liver fibrosis by inhibiting Stat6 signalling pathway

This study aims to explore the effect of Corilagin (Cor) on post-parasiticide schistosome egg-induced hepatic fibrosis through the Stat6 signalling pathway in vitro and in vivo. Cellular and animal models were established and treated by Corilagin. The inhibitory effect of Corilagin was also confirmed in RAW264.7 cells in which Stat6 was overexpressed based on the GV367-Stat6-EGFP lentiviral vector system and in which Stat6 was knock-downed by gene specific siRNAs. As a result, Corilagin prevented increases in the protein level of Phospho-Stat6 (P-Stat6). Both the mRNA and protein levels of the downstream mediators SOCS1, KLF4, and PPAR{gamma}/{delta} were markedly suppressed after Corilagin treatment. Expression of ARG1 and FIZZ1/Retnla, Ym1, TGF-{beta} and PDGF in serum were also inhibited by Corilagin. The pathological changes, area of granulomas of liver sections, and degree of hepatic fibrosis were significantly alleviated in the Corilagin group. The areas of CD68- and CD206-positive cells stained by immunofluorescence were significantly decreased by Corilagin. In conclusion, Corilagin can suppress post-parasiticide schistosome egg-induced hepatic fibrosis by inhibiting the Stat6 signalling pathway and provide a new therapeutic strategy for schistosomiasis liver fibrosis.

pharmacology and toxicology↗

bioRxiv2018

Disrupted structure and aberrant function of CHIP mediates the loss of motor and cognitive function in preclinical models of cerebellar CHIPopathy

CHIP (carboxyl terminus of heat shock 70-interacting protein) has long been recognized as an active member of the cellular protein quality control system given the ability of CHIP to function as both a co-chaperone and ubiquitin ligase. Mutations in CHIP are the driver of spinocerebellar autosomal recessive 16 (SCAR16), or cerebellar CHIPopathy, as we initially discovered this disease was caused by a loss of CHIP ubiquitin ligase function. The initial mutation describing SCAR16 was a missense mutation in the ubiquitin ligase domain of CHIP (p.T246M). Using multiple biophysical and cellular approaches, we demonstrate that T246M mutation results in structural disorganization and misfolding of the CHIP U-box domain, promoting oligomerization, and increased proteasome-dependent turnover. CHIP-T246M has no ligase activity, but maintains interactions with chaperones and alters the co-chaperone function of CHIP. To establish preclinical models of SCAR16, we engineered T246M at the endogenous locus in both mice and rats. Animals homozygous for T246M had both cognitive and motor cerebellar dysfunction distinct from those observed in the CHIP null animal model, as well as deficits in learning and memory, reflective of the cognitive deficits reported in SCAR16 patients. We conclude that the T246M mutation is not equivalent to the total loss of CHIP, supporting the concept that disease-causing CHIP mutations have different biophysical and functional repercussions on CHIP function that may directly correlate to the spectrum of clinical phenotypes observed in SCAR16 patients. Our findings both further expand our basic understanding of CHIP biology and provide meaningful mechanistic insight underlying the molecular drivers of SCAR16 disease pathology, which may be used to inform the development of novel therapeutics for this devastating disease.

animal behavior and cognition↗