Research on the roles of genes coding ATP-binding cassette transporters in Porphyromonas gingivalis pathogenicity

Porphyromonas gingivalis, as a major pathogen of periodontitis, could rapidly adhere to and invade host gingival epithelial cells (GECs) for the induction of infection. One ATP-binding cassette (ABC) transporter gene was found to be upregulated during this infection process, however, the molecular mechanisms remain unclear. In this study, we systemically investigated the messenger RNA level changes of all ABC transporter family genes in P. gingivalis while being internalized within GECs by real-time polymerase chain reaction. We identified that two ABC transporter genes, PG_RS04465 (PG1010) and PG_RS07320 (PG1665), were significantly increased in P. gingivalis after coculturing with GECs. Mutant strains with knockout (KO) of these two genes were generated by homogenous recombination. PG_RS04465 and PG_RS07320 KO mutants showed no change in the growth of bacteria per se. Knockdown of PG_RS07320, but not PG_RS04465, caused decreased endotoxin level in the bacteria. In contrast, both mutant strains showed decreased Arg- and Lys-gingipains activities, with significantly reduced adhesion and invasion capabilities. Secreted interleukin-1β (IL-1β) and IL-6 levels in GECs cocultured with PG_RS04465 or PG_RS07320 KO mutants were also decreased, whereas, only the cells cocultured with PG_RS07320 KO mutants showed significant decrease. In addition, virulence study using mouse revealed that both KO mutant strains infection caused less mouse death than wild-type strains, showing reduced virulence of two KO strains. These results indicated that ABC transporter genes PG_RS04465 and PG_RS07320 are positive regulators of the virulence of P. gingivalis.     

Histopathology,Molecular Identification and Antifungal Susceptibility Testing of Nannizziopsis arthrosporioides from a Captive Cuban Rock Iguana (Cyclura nubila)

Mycopathologia - Chrysosporium-related fungi, the cause of superficial and deep mycoses, are an emerging infectious disease affecting not only reptiles but also immunocompromized humans. However,...     

Amyloid precursor protein is a restriction factor that protects against Zika virus infection in mammalian brains

Zika virus (ZIKV) is a neurotropic flavivirus that causes several diseases including birth defects such as microcephaly. Intrinsic immunity is known to be a frontline defense against viruses through host anti-viral restriction factors. Limited knowledge is available on intrinsic immunity against ZIKV in brains. Amyloid precursor protein (APP) is predominantly expressed in brains and implicated in the pathogenesis of Alzheimer''s diseases. We have found that ZIKV interacts with APP, and viral infection increases APP expression via enhancing protein stability. Moreover, we identified the viral peptide, HGSQHSGMIVNDTGHETDENRAKVEITPNSPRAEATLGGFGSLGL, which is capable of en-hancing APP expression. We observed that aging brain tissues with APP had protective effects on ZIKV infection by reducing the availability of the viruses. Also, knockdown of APP expression or blocking ZIKV-APP interactions enhanced ZIKV replication in human neural progenitor/stem cells. Finally, intracranial infection of ZIKV in APP-null neonatal mice resulted in higher mortality and viral yields. Taken together, these findings suggest that APP is a restriction factor that protects against ZIKV by serving as a decoy receptor, and plays a protective role in ZIKV-mediated brain injuries.     

Association of polymorphisms in the Chr18q11.2 locus with tuberculosis in Chinese population

A GWAS study has reported that two single nucleotide polymorphisms (SNPs) were associated with predisposition to tuberculosis (TB) in African populations. These two loci represented the long-waited GWAS hits for TB susceptibility. To determine whether these two SNPs are associated with TB in Chinese population, we attempted an replication in a cohort of over one thousand Chinese TB patients and 1,280 healthy controls using melting temperature shift allele-specific genotyping analysis. We found that only SNP rs4331426 was significantly associated with TB in Chinese population (p = 0.011). However, the effect was opposite. The G allele of the SNP in Chinese population is a protective allele (OR = 0.62, 95 % CI 0.44–0.87), while it was the risk allele for African population (OR = 1.19, 95 % CI 1.12–1.26). No significance was found for SNP rs2335704. The results provided an independent support for a role in susceptibility to TB for SNP rs4331426. However, it also indicated that direct predisposition element to TB and the association effects may vary across ethnic groups.     

Ubc9 acetylation modulates distinct SUMO target modification and hypoxia response

While numerous small ubiquitin‐like modifier (SUMO) conjugated substrates have been identified, very little is known about the cellular signalling mechanisms that differentially regulate substrate sumoylation. Here, we show that acetylation of SUMO E2 conjugase Ubc9 selectively downregulates the sumoylation of substrates with negatively charged amino acid‐dependent sumoylation motif (NDSM) consisting of clustered acidic residues located downstream from the core ψ‐K‐X‐E/D consensus motif, such as CBP and Elk‐1, but not substrates with core ψ‐K‐X‐E/D motif alone or SUMO‐interacting motif. Ubc9 is acetylated at residue K65 and K65 acetylation attenuates Ubc9 binding to NDSM substrates, causing a reduction in NDSM substrate sumoylation. Furthermore, Ubc9 K65 acetylation can be downregulated by hypoxia via SIRT1, and is correlated with hypoxia‐elicited modulation of sumoylation and target gene expression of CBP and Elk‐1 and cell survival. Our data suggest that Ubc9 acetylation/deacetylation serves as a dynamic switch for NDSM substrate sumoylation and we report a previously undescribed SIRT1/Ubc9 regulatory axis in the modulation of protein sumoylation and the hypoxia response.     

Aly and THO are required for assembly of the human TREX complex and association of TREX components with the spliced mRNA

The mRNA export complex TREX (TREX) is known to contain Aly, UAP56, Tex1 and the THO complex, among which UAP56 is required for TREX assembly. Here, we systematically investigated the role of each human TREX component in TREX assembly and its association with the mRNA. We found that Tex1 is essentially a subunit of the THO complex. Aly, THO and UAP56 are all required for assembly of TREX, in which Aly directly interacts with THO subunits Thoc2 and Thoc5. Both Aly and THO function in linking UAP56 to the cap-binding protein CBP80. Interestingly, association of UAP56 with the spliced mRNA, but not with the pre-mRNA, requires Aly and THO. Unexpectedly, we found that Aly and THO require each other to associate with the spliced mRNA. Consistent with these biochemical results, similar to Aly and UAP56, THO plays critical roles in mRNA export. Together, we propose that Aly, THO and UAP56 form a highly integrated unit to associate with the spliced mRNA and function in mRNA export.     

Improved protective efficacy of a chimeric Staphylococcus aureus vaccine candidate iron‐regulated surface determinant B (N126–P361)‐target of RNAIII activating protein in mice

The pathogen Staphylococcus aureus causes a wide range of serious infections, necessitating urgent development of a vaccine against this organism. However, currently developed vaccines are relatively ineffective because of the limited antigenic component that is contained in the vaccine formulations. To develop an effective S. aureus candidate vaccine, overlapping PCR was used to add the truncated immunodominant antigen iron‐regulated surface determinant B (IsdB)_{(N126–P361)} (tIsdB) to the N‐terminal of intact antigen target of RNAIII activating protein (TRAP) and thus construct a tIsdB‐TRAP chimera. The humoral and cellular immune responses against tIsdB‐TRAP were compared with those against single or combined formulations. tIsdB‐TRAP elicited significantly stronger humoral responses in mice (P < 0.05). As to cellular immune responses in mice, the tIsdB‐TRAP group resulted in a greater IL‐4 response than did other groups (P < 0.05). Greater amounts of IL‐2 and IFN‐γ were found in the tIsdB‐TRAP group. Mouse challenge also showed that tIsdB‐TRAP provided better protection against S. aureus than did the control groups. These results suggest that this chimeric protein may be a promising pathogen target for further vaccine development.