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Articles by Marija Pinne in JoVE
JoVE Immunology and Infection
Immuno Assay-fluorescentie van Leptospiral Surface-blootgesteld Eiwitten
1Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, 2Research service, 151, Veterans Affairs Greater Los Angeles Healthcare System, 3Departments of Medicine, Urology at David Geffen School of Medicine and Department of Microbiology, Immunology and Molecular Gentics, University of California Los Angeles (UCLA), 4Division of Infectious Diseases, 111F, Veterans Affairs Greater Los Angeles Health Care System
Een efficiënte methode om het oppervlak-blootstelling van leptospiral eiwitten te bepalen is beschreven. De methode is speciaal ontworpen om verstoring van de kwetsbare buitenste membraan van leptospiral cellen te voorkomen. Deze techniek vergt inzet van een aantal negatieve controles te beoordelen van de integriteit van de buitenste membraan en de specificiteit van de antistof reactie.
Other articles by Marija Pinne on PubMed
Elimination of Channel-forming Activity by Insertional Inactivation of the P13 Gene in Borrelia Burgdorferi
P13 is a chromosomally encoded 13-kDa integral outer membrane protein of the Lyme disease agent, Borrelia burgdorferi. The aim of this study was to investigate the function of the P13 protein. Here, we inactivated the p13 gene by targeted mutagenesis and investigated the porin activities of outer membrane proteins by using lipid bilayer experiments. Channel-forming activity was lost in the p13 mutant compared to wild-type B. burgdorferi, indicating that P13 may function as a porin. We purified native P13 to homogeneity by fast performance liquid chromatography and demonstrated that pure P13 has channel-forming activity with a single-channel conductance in 1 M KCl of 3.5 nS, the same as the porin activity that was lost in the p13 mutant. Further characterization of the channel formed by P13 suggested that it is cation selective and voltage independent. In addition, no major physiological effects of the inactivated p13 gene could be detected under normal growth conditions. The inactivation of p13 is the first reported inactivation of a gene encoding an integral outer membrane protein in B. burgdorferi. Here, we describe both genetic and biophysical experiments indicating that P13 in B. burgdorferi is an outer membrane protein with porin activity.
Molecular Analysis of the Channel-forming Protein P13 and Its Paralogue Family 48 from Different Lyme Disease Borrelia Species
The aetiological agent of Lyme disease, Borrelia burgdorferi cycles between its tick vector and mammalian hosts, implying that it can sense different environments and consequently change the expression of genes encoding several surface-associated proteins. The genome of the type strain B. burgdorferi B31 has revealed 175 different gene families. The p13 gene, situated on the chromosome, encodes a channel-forming protein that belongs to the gene family 48 consisting of eight additional paralogous genes. The heterogeneity of the P13 protein from different Lyme disease Borrelia strains was investigated. The predicted surface-exposed domains are the most heterogeneous regions and contain probable epitopes of P13. The membrane-spanning architecture of P13 was determined and a model for the location of this protein in the outer membrane is presented. The transcription of the paralogues of gene family 48 during in vitro culturing and in a mouse infection model was also analysed. The bba01 gene is the only p13 paralogue present in all three Lyme-disease-causing genospecies; it is stable during cultivation in vitro and the BBA01 protein was expressed in all Borrelia strains investigated. Conversely, paralogues bbi31, bbq06 and bbh41 were only detected in B. burgdorferi and the corresponding plasmids harbouring bbi31 and bbh41 were lost during in vitro passage. Finally, p13 and bbi31 are the only members of gene family 48 that are transcribed in mice, suggesting their importance during mammalian infection.
Pleiotropic Effects of Inactivating a Carboxyl-terminal Protease, CtpA, in Borrelia Burgdorferi
A gene encoding a putative carboxyl-terminal protease (CtpA), an unusual type of protease, is present in the Borrelia burgdorferi B31 genome. The B. burgdorferi CtpA amino acid sequence exhibits similarities to the sequences of the CtpA enzymes of the cyanobacterium Synechocystis sp. strain PCC 6803 and higher plants and also exhibits similarities to the sequences of putative CtpA proteins in other bacterial species. Here, we studied the effect of ctpA gene inactivation on the B. burgdorferi protein expression profile. Total B. burgdorferi proteins were separated by two-dimensional gel electrophoresis, and the results revealed that six proteins of the wild type were not detected in the ctpA mutant and that nine proteins observed in the ctpA mutant were undetectable in the wild type. Immunoblot analysis showed that the integral outer membrane protein P13 was larger and had a more acidic pI in the ctpA mutant, which is consistent with the theoretical change in pI for P13 not processed at the carboxyl terminus. Matrix-assisted laser desorption ionization-time of flight data indicated that in addition to P13, the BB0323 protein may serve as a substrate for carboxyl-terminal processing by CtpA. Complementation analysis of the ctpA mutant provided strong evidence that the observed effect on proteins depended on inactivation of the ctpA gene alone. We show that CtpA in B. burgdorferi is involved in the processing of proteins such as P13 and BB0323 and that inactivation of ctpA has a pleiotropic effect on borrelial protein synthesis. To our knowledge, this is the first analysis of both a CtpA protease and different substrate proteins in a pathogenic bacterium.
The BBA01 Protein, a Member of Paralog Family 48 from Borrelia Burgdorferi, is Potentially Interchangeable with the Channel-forming Protein P13
The Borrelia burgdorferi genome exhibits redundancy, with many plasmid-carried genes belonging to paralogous gene families. It has been suggested that certain paralogs may be necessary in various environments and that they are differentially expressed in response to different conditions. The chromosomally located p13 gene which codes for a channel-forming protein belongs to paralog family 48, which consists of eight additional genes. Of the paralogous genes from family 48, the BBA01 gene has the highest homology to p13. Herein, we have inactivated the BBA01 gene in B. burgdorferi strain B31-A. This mutant shows no apparent phenotypic difference compared to the wild type. However, analysis of BBA01 in a C-terminal protease A (CtpA)-deficient background revealed that like P13, BBA01 is posttranslationally processed at its C terminus. Elevated BBA01 expression was obtained in strains with the BBA01 gene introduced on the shuttle vector compared to the wild-type strain. We could further demonstrate that BBA01 is a channel-forming protein with properties surprisingly similar to those of P13. The single-channel conductance, of about 3.5 nS, formed by BBA01 is comparable to that of P13, which together with the high degree of sequence similarity suggests that the two proteins may have similar and interchangeable functions. This is further strengthened by the up-regulation of the BBA01 protein and its possible localization in the outer membrane in a p13 knockout strain, thus suggesting that P13 can be replaced by BBA01.
Elimination of Channel-forming Activity by Insertional Inactivation of the P66 Gene in Borrelia Burgdorferi
P66 is a chromosomally encoded 66-kDa integral outer membrane protein of the Lyme disease agent Borrelia burgdorferi exhibiting channel-forming activity. Herein, we inactivated and subsequently complemented the p66 gene in the B31-A (WT) strain. The P66 protein was also inactivated in two other channel-forming protein mutant strains, P13-18 (Deltap13) and Deltabba01, and then compared with the channel-forming activities of wild-type and various p66 mutant strains. We further investigated the ion-selectivity of native, purified P66. In conclusion, we show that the porin activity of P66 is eliminated by insertional inactivation and that this activity can be rescued by gene complementation.
Leptospira Interrogans Endostatin-like Outer Membrane Proteins Bind Host Fibronectin, Laminin and Regulators of Complement
The pathogenic spirochete Leptospira interrogans disseminates throughout its hosts via the bloodstream, then invades and colonizes a variety of host tissues. Infectious leptospires are resistant to killing by their hosts' alternative pathway of complement-mediated killing, and interact with various host extracellular matrix (ECM) components. The LenA outer surface protein (formerly called LfhA and Lsa24) was previously shown to bind the host ECM component laminin and the complement regulators factor H and factor H-related protein-1. We now demonstrate that infectious L. interrogans contain five additional paralogs of lenA, which we designated lenB, lenC, lenD, lenE and lenF. All six genes encode domains predicted to bear structural and functional similarities with mammalian endostatins. Sequence analyses of genes from seven infectious L. interrogans serovars indicated development of sequence diversity through recombination and intragenic duplication. LenB was found to bind human factor H, and all of the newly-described Len proteins bound laminin. In addition, LenB, LenC, LenD, LenE and LenF all exhibited affinities for fibronectin, a distinct host extracellular matrix protein. These characteristics suggest that Len proteins together facilitate invasion and colonization of host tissues, and protect against host immune responses during mammalian infection.
A Comprehensive Approach to Identification of Surface-exposed, Outer Membrane-spanning Proteins of Leptospira Interrogans
Leptospirosis is a zoonosis with worldwide distribution caused by pathogenic spirochetes belonging to the genus Leptospira. The leptospiral life cycle involves transmission via fresh water and colonization of the renal tubules of their reservoir hosts or infection of accidental hosts, including humans. Bacterial outer membrane proteins (OMPs), particularly those with surface-exposed regions, play crucial roles in virulence mechanisms of pathogens and the adaptation to various environmental conditions, including those of the mammalian host. Little is known about the surface-exposed OMPs in Leptospira, particularly those with outer membrane-spanning domains. Herein, we describe a comprehensive strategy for identification and characterization of leptospiral transmembrane OMPs. The genomic sequence of L. interrogans serovar Copenhageni strain Fiocruz L1-130 allowed us to employ the beta-barrel prediction programs, PRED-TMBB and TMBETA-NET, to identify potential transmembrane OMPs. Several complementary methods were used to characterize four novel OMPs, designated OmpL36, OmpL37, OmpL47 and OmpL54. In addition to surface immunofluorescence and surface biotinylation, we describe surface proteolysis of intact leptospires as an improved method for determining the surface exposure of leptospiral proteins. Membrane integration was confirmed using techniques for removal of peripheral membrane proteins. We also demonstrate deficiencies in the Triton X-114 fractionation method for assessing the outer membrane localization of transmembrane OMPs. Our results establish a broadly applicable strategy for the elucidation of novel surface-exposed outer membrane-spanning proteins of Leptospira, an essential step in the discovery of potential virulence factors, diagnostic antigens and vaccine candidates.
The OmpL37 Surface-exposed Protein is Expressed by Pathogenic Leptospira During Infection and Binds Skin and Vascular Elastin
Pathogenic Leptospira spp. shed in the urine of reservoir hosts into freshwater can be transmitted to a susceptible host through skin abrasions or mucous membranes causing leptospirosis. The infection process involves the ability of leptospires to adhere to cell surface and extracellular matrix components, a crucial step for dissemination and colonization of host tissues. Therefore, the elucidation of novel mediators of host-pathogen interaction is important in the discovery of virulence factors involved in the pathogenesis of leptospirosis. In this study, we assess the functional roles of transmembrane outer membrane proteins OmpL36 (LIC13166), OmpL37 (LIC12263), and OmpL47 (LIC13050), which we recently identified on the leptospiral surface. We determine the capacity of these proteins to bind to host tissue components by enzyme-linked immunosorbent assay. OmpL37 binds elastin preferentially, exhibiting dose-dependent, saturating binding to human skin (K(d), 104±19 nM) and aortic elastin (K(d), 152±27 nM). It also binds fibrinogen (K(d), 244±15 nM), fibrinogen fragment D (K(d), 132±30 nM), plasma fibronectin (K(d), 359±68 nM), and murine laminin (K(d), 410±81 nM). The binding to human skin elastin by both recombinant OmpL37 and live Leptospira interrogans is specifically enhanced by rabbit antiserum for OmpL37, suggesting the involvement of OmpL37 in leptospiral binding to elastin and also the possibility that host-generated antibodies may promote rather than inhibit the adherence of leptospires to elastin-rich tissues. Further, we demonstrate that OmpL37 is recognized by acute and convalescent leptospirosis patient sera and also by Leptospira-infected hamster sera. Finally, OmpL37 protein is detected in pathogenic Leptospira serovars and not in saprophytic Leptospira. Thus, OmpL37 is a novel elastin-binding protein of pathogenic Leptospira that may be promoting attachment of Leptospira to host tissues.
Methylation and in Vivo Expression of the Surface-exposed Leptospira Interrogans Outer Membrane Protein OmpL32
Recent studies have revealed that bacterial protein methylation is a widespread post-translational modification that is required for virulence in selected pathogenic bacteria. In particular, altered methylation of outer membrane proteins has been shown to modulate the effectiveness of the host immune response. In this study, two-dimensional gel electrophoresis combined with matrix-assisted laser desorption/ionization-time of flight mass spectrometry identified a Leptospira interrogans serovar Copenhageni strain Fiocruz L1-130 protein, corresponding to open reading frame (ORF) LIC11848, which undergoes extensive and differential methylation of glutamic acid residues. Immunofluorescence microscopy implicated LIC11848 as a surface-exposed outer membrane protein, prompting the designation OmpL32. Indirect immunofluorescence microscopy of golden Syrian hamster liver and kidney sections revealed expression of OmpL32 during colonization of these organs. Identification of methylated surface-exposed outer membrane proteins, such as OmpL32, provides a foundation for delineating the role of this post-translational modification in leptospiral virulence.
Antibodies to a Novel Leptospiral Protein, LruC, in the Eye Fluids and Sera of Horses with Leptospira-associated Uveitis
Screening of an expression library of Leptospira interrogans with eye fluids from uveitic horses resulted in identification of a novel protein, LruC. LruC is located in the inner leaflet of leptospiral outer membrane and an lruC gene was detected in all tested pathogenic L. interrogans. LruC-specific antibody levels were significantly higher in eye fluids and sera of uveitic horses than healthy horses. These findings suggest that LruC may play a role in equine leptospiral uveitis.
