Search tips
Search criteria

Results 1-5 (5)

Clipboard (0)

Select a Filter Below

more »
Year of Publication
Document Types
1.  Matrix Metalloproteinase 9 Plays a Key Role in Lyme Arthritis but Not in Dissemination of Borrelia burgdorferi▿  
Infection and Immunity  2009;77(7):2643-2649.
Borrelia burgdorferi, the causative agent of Lyme arthritis, does not produce any exported proteases capable of degrading extracellular matrix despite the fact that it is able to disseminate from a skin insertion site to infect multiple organs. Prior studies have shown that B. burgdorferi induces the host protease, matrix metalloproteinase 9 (MMP-9), and suggested that the induction of MMP-9 may allow the organism to disseminate and produce local tissue destruction. We examined the role of MMP-9 in dissemination of B. burgdorferi and pathogenesis of Lyme arthritis. In a MMP-9−/− mouse model, MMP-9 was not required for the dissemination of the spirochete to distant sites. However, MMP-9−/− exhibited significantly decreased arthritis compared to wild-type mice. The decrease in arthritis was not due to an inability to control infection since the spirochete numbers in the joints were identical. Levels of inflammatory chemokines and cytokines were also similar in MMP-9−/− and wild-type mice. We examined whether decreased inflammation in MMP-9−/− mice may be the result of decreased production of neoattractants by MMP-9-dependent cleavage of collagen. MMP-9 cleavage of type I collagen results in increased monocyte chemoattraction. MMP-9 plays an important role in regulating inflammation in Lyme arthritis, potentially through the cleavage of type I collagen.
PMCID: PMC2708580  PMID: 19364840
2.  pIIICTX, a Predicted CTXφ Minor Coat Protein, Can Expand the Host Range of Coliphage fd To Include Vibrio cholerae 
Journal of Bacteriology  2003;185(3):1037-1044.
CTXφ is a filamentous bacteriophage that encodes cholera toxin. CTXφ infection of its host bacterium, Vibrio cholerae, requires the toxin-coregulated pilus (TCP) and the products of the V. cholerae tolQRA genes. Here, we have explored the role of OrfU, a predicted CTXφ minor coat protein, in CTXφ infection. Prior to the discovery that it was part of a prophage, orfU was initially described as an open reading frame of unknown function that lacked similarity to known protein sequences. Based on its size and position in the CTXφ genome, we hypothesized that OrfU may function in a manner similar to that of the coliphage fd protein pIII and mediate CTXφ infection as well as playing a role in CTXφ assembly and release. Deletion of orfU from CTXφ dramatically reduced the number of CTXφ virions detected in supernatants from CTXφ-bearing cells. This defect was complemented by expression of orfU in trans, thereby confirming a role for this gene in CTXφ assembly and/or release. To evaluate the requirement for OrfU in CTXφ infection, we introduced fragments of orfU into gIII in an fd derivative to create OrfU-pIII fusions. While fd is ordinarily unable to infect V. cholerae, an fd phage displaying the N-terminal 274 amino acids of OrfU could infect V. cholerae in a TCP- and TolA-dependent fashion. Since our findings indicate that OrfU functions as the CTXφ pIII, we propose to rename OrfU as pIIICTX. Our data also provide new evidence for a conserved pathway for filamentous phage infection.
PMCID: PMC142820  PMID: 12533480
3.  Molecular Analyses of a Putative CTXφ Precursor and Evidence for Independent Acquisition of Distinct CTXφs by Toxigenic Vibrio cholerae 
Journal of Bacteriology  2000;182(19):5530-5538.
The genes encoding cholera toxin (ctxA and ctxB) are encoded in the genome of CTXφ, a filamentous phage that infects Vibrio cholerae. To study the evolutionary history of CTXφ, we examined genome diversity in CTXφs derived from a variety of epidemic and nonepidemic Vibrio sp. natural isolates. Among these were three V. cholerae strains that contained CTX prophage sequences but not the ctxA and ctxB genes. These prophages each gave rise to a plasmid form whose genomic organization was very similar to that of the CTXφ replicative form, with the exception of missing ctxAB. Sequence analysis of these three plasmids revealed that they lacked the upstream control region normally found 5′ of ctxA, as well as the ctxAB promoter region and coding sequences. These findings are consistent with the hypothesis that a CTXφ precursor that lacked ctxAB simultaneously acquired the toxin genes and their regulatory sequences. To assess the evolutionary relationships among additional CTXφs, two CTXφ-encoded genes, orfU and zot, were sequenced from 13 V. cholerae and 4 V. mimicus isolates. Comparative nucleotide sequence analyses revealed that the CTXφs derived from classical and El Tor V. cholerae isolates comprise two distinct lineages within otherwise nearly identical chromosomal backgrounds (based on mdh sequences). These findings suggest that nontoxigenic precursors of the two V. cholerae O1 biotypes independently acquired distinct CTXφs.
PMCID: PMC110998  PMID: 10986258
4.  The Carboxyl Terminus of v-Abl Protein Can Augment SH2 Domain Function 
Journal of Virology  2000;74(10):4495-4504.
Abelson murine leukemia virus (Ab-MLV) transforms NIH 3T3 and pre-B cells via expression of the v-Abl tyrosine kinase. Although the enzymatic activity of this molecule is absolutely required for transformation, other regions of the protein are also important for this response. Among these are the SH2 domain, involved in phosphotyrosine-dependent protein-protein interactions, and the long carboxyl terminus, which plays an important role in transformation of hematopoietic cells. Important signals are sent from each of these regions, and transformation is most likely orchestrated by the concerted action of these different parts of the protein. To explore this idea, we compared the ability of the v-Src SH2 domain to substitute for that of v-Abl in the full-length P120 v-Abl protein and in P70 v-Abl, a protein that lacks the carboxyl terminus characteristic of Abl family members. Ab-MLV strains expressing P70/S2 failed to transform NIH 3T3 cells and demonstrated a greatly reduced capacity to mediate signaling events associated with the Ras-dependent mitogen-activated protein (MAP) kinase pathway. In contrast, Ab-MLV strains expressing P120/S2 were indistinguishable from P120 with respect to these features. Analyses of additional mutants demonstrated that the last 162 amino acids of the carboxyl terminus were sufficient to restore transformation. These data demonstrate that an SH2 domain with v-Abl substrate specificity is required for NIH 3T3 transformation in the absence of the carboxyl terminus and suggest that cooperativity between the extreme carboxyl terminus and the SH2 domain facilitates the transmission of transforming signals via the MAP kinase pathway.
PMCID: PMC111963  PMID: 10775585
5.  CTXφ Infection of Vibrio cholerae Requires the tolQRA Gene Products 
Journal of Bacteriology  2000;182(6):1739-1747.
CTXφ is a lysogenic filamentous bacteriophage that encodes cholera toxin. Filamentous phages that infect Escherichia coli require both a pilus and the products of tolQRA in order to enter host cells. We have previously shown that toxin-coregulated pilus (TCP), a type IV pilus that is an essential Vibrio cholerae intestinal colonization factor, serves as a receptor for CTXφ. To test whether CTXφ also depends upon tol gene products to infect V. cholerae, we identified and inactivated the V. cholerae tolQRAB orthologues. The predicted amino acid sequences of V. cholerae TolQ, TolR, TolA, and TolB showed significant similarity to the corresponding E. coli sequences. V. cholerae strains with insertion mutations in tolQ, tolR, or tolA were reduced in their efficiency of CTXφ uptake by 4 orders of magnitude, whereas a strain with an insertion mutation in tolB showed no reduction in CTXφ entry. We could detect CTXφ infection of TCP− V. cholerae, albeit at very low frequencies. However, strains with mutations in both tcpA and either tolQ, tolR, or tolA were completely resistant to CTXφ infection. Thus, CTXφ, like the E. coli filamentous phages, uses both a pilus and TolQRA to enter its host. This suggests that the pathway for filamentous phage entry into cells is conserved between host bacterial species.
PMCID: PMC94473  PMID: 10692381

Results 1-5 (5)