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PubMed1983

Role for DNA homology in site-specific recombination. The isolation and characterization of a site affinity mutant of coliphage lambda.

Site-affinity (or saf) mutations change the specificity of prophage insertion. We have isolated a saf mutation of the bacteriophage lambda attachment site by inserting the phage chromosome into and then excising it from a secondary host attachment site. This causes reciprocal exchange of two seven base-pair segments (the overlap regions) that lie within the cores of the two sites. Since the two overlap regions differ from each other in nucleotide sequence, the recombinant sites are mutants. We have determined the effect of overlap region homology on recombination. We found that homology promotes integrative and excisive recombination. This suggests that the two overlap regions interact directly during recombination. The pattern of segregation of the saf mutation during site-specific recombination shows that it lies to the right of the point of genetic exchange about 95% of the time. This is a surprising result because lambda integrative recombination normally occurs by two staggered, reciprocal single-strand exchanges, one at each edge of the overlap region (Mizuuchi et al., 1981). Since saf lies within the overlap region, we might have expected that the point of genetic exchange would occur to the left of saf as often as to the right. We offer two models to account for this. (1) The mutation alters the location of one of the single-strand exchange points. (2) Efficient and strand-specific processing of mismatched base-pairs changes the expected segregation pattern.

Attachment Sites, Microbiological↗

PubMedDate not supplied

[The ultrastructural characteristics of the histopathological changes at the site of attachment to the host body of larvae of the ixodid tick Ixodes ricinus].

The attachment of ixodid tick Ixodes ricinus larvae to white mice and histopathology of host tissue in the attachment site were investigated by means of electronic microscopy. It was demonstrated the presence of cement substance around the mouthparts of tick during the first and the second days of feeding period and the absence of it at the last day of this period. The cement substance consists only of the cement cone (the external cement), situated on the surface of host epidermis. The tick mouthparts in the host dermis were surrounded by zone of modified collagene fibers. Examination of feeding site showed the intensive neutrophil migration and the formation of feeding cavity in 2 days after attachment of tick. At the same time the erythrocytes and active fibroblasts were found in the feeding cavity.

Animals↗

PubMed2001

Adhesive secretions in the Platyhelminthes.

This review is the first to draw together knowledge about bioadhesives secreted by a group of parasites. Mechanisms of mechanical attachment are well known among parasites, but some can also attach to host surfaces by chemical means using a thin layer of adhesive material secreted at the parasite-host interface. Attachment by adhesives to living surfaces has not been studied in detail previously. A significant volume of research has determined much about the chemistry and nature of bioadhesives secreted by various marine macroinvertebrates from different phyla for attachment to inert substrates. Mussels and barnacles are sessile and adhere permanently, whereas starfish display temporary but firm adhesion during locomotion, feeding and burrowing. We focus on the Platyhelminthes that comprises the largely free-living Turbellaria and the wholly parasitic Monogenea, Cestoda, Digenea and Aspidogastrea. The term tissue adhesion is introduced to describe attachment by adhesives to epithelial surfaces such as fish epidermis and the lining of the vertebrate gut. These living layers regenerate rapidly, secrete mucus, are a site for immune activity and are therefore especially hostile environments for organisms that inhabit them, presenting a significant challenge for adhesion. Not all platyhelminths adhere to living surfaces and types of adhesion to inert substrates by the free-living turbellarians are also reviewed. Tissue adhesion is particularly well exemplified by monopisthocotylean monogeneans, parasites that are especially mobile as larvae, juveniles and adults on the epidermis of the body and gill surfaces of fish. These monogeneans secrete adhesives from the anterior end when they move from site to site, but some have secondarily developed adhesives at the posterior end to supplement or replace mechanical attachment by hooks and/or by suction. The temporary but tenacious anterior adhesives of monogeneans display remarkable properties of instant attachment to and detachment from their host fish surfaces. In contrast to the mobility of turbellarians and monopisthocotylean monogeneans and the simplicity of their direct life cycles, the largely endoparasitic Cestoda and Digenea are considered to be less mobile as adults. The complex cestode and digenean life cycles, involving intermediate hosts, place different demands on their various stages. Diverse, mostly anterior, gland cells in larvae, metacestodes and adults of the true tapeworms (Eucestoda), and in larval and adult Gyrocotylidea and Amphilinidea are reviewed. Conspicuous gland cells, mostly but not exclusively at the anterior end, in miracidia, cercariae and adults of digeneans and in cotylocidia and adults of aspidogastreans are also reviewed. Unlike turbellarians and monogeneans, accounts of unequivocal adhesive secretions in the Cestoda, but especially in the Digenea and Aspidogastrea, are relatively rare. The primary purpose of many conspicuous glands in the different stages of these mostly endoparasitic flatworms is for penetration into, or escape from, different hosts in their life cycle. We provide a detailed review of current knowledge about adhesion (in the sense of a thin layer of chemical material) in the Platyhelminthes including uses among eggs, larval, juvenile and adult stages. Information on structure, morphology and ultrastructure of the various adhesive systems that have been described is reviewed. Application of the 'duo gland' model is discussed. Comparisons are made between the little that is known about the chemistry of flatworm adhesives and the significant knowledge of the chemical nature of other invertebrate bioadhesives, especially those from marine macroinvertebrates. The potential importance of adhesives in parasitism is discussed. (ABSTRACT TRUNCATED)

Animals↗

PubMed2006

Evolution of immunity and host chromosome integration site of P2-like coliphages.

The amount and distribution of variation in the genomic region containing the genes in the lytic-lysogenic genetic switch and the sequence that determines the integration site into the host chromosome were analyzed for 38 P2-like phages from Escherichia coli. The genetic switch consists of two convergent mutually exclusive promoters, Pe and Pc, and two repressors, C and Cox. The immunity repressor C blocks the early Pe promoter, leading to the establishment of lysogeny. The Cox repressor blocks expression of Pc, allowing lytic growth. Phylogenetic analyses showed that the C and Cox proteins were distributed into seven distinct classes. The phylogenetic relationship differed between the two proteins, and we showed that homologous recombination plays a major role in creating alterations in the genetic switch, leading to new immunity classes. Analyses of the host integration site for these phages resulted in the discovery of a previously unknown site, and there were at least four regular integration sites. Interestingly, we found no case where phages of the same immunity class had different host attachment sites. The evolution of immunity and integration sites is complex, since it involves interactions both between the phages themselves and between phages and hosts, and often, both regulatory proteins and target DNA must change.

Amino Acid Sequence↗

PubMed1985

Excision and reintegration of the Escherichia coli K-12 chromosomal element e14.

The genetic element e14 is a natural component of the Escherichia coli K-12 chromosome. On induction of the SOS pathways, e14 excises as a 14.4-kilobase circle. We report here on the reintegration of e14 into the chromosome of cured (e14 degrees) E. coli K-12 derivatives. Using a Tn10 insertion mutant of e14, we found that reintegration occurred specifically at the locus originally occupied by e14 and with the same orientation. The reintegration event required neither the RecA nor the RecB functions. The attachment site of the free form was located within a 950-base-pair HindIII-AvaI fragment and shared sufficient homology with the host attachment site to form detectable DNA-DNA hybrids. Even though E. coli C and B/5 did not contain e14, they did possess a HindIII restriction fragment that hybridized to the free e14 attachment fragment. E. coli C could be transformed with e14-1272::Tn10, resulting in integration at this site of homology. The Tn10 mutants were also used in mapping the point of e14 attachment. We found the following sequence: fabD purB atte14 umuC. Furthermore, analysis of a recombinant plasmid that contained both the e14 attachment site and the purB locus showed that these two loci occur within 11 kilobases of each other.

Chromosome Mapping↗

PubMed1985

Immature and mature neurofilament-immunoreactive trigeminal fibers can innervate the iris as studied by intraocular grafting of iris and trigeminal ganglia.

Using immunohistochemistry on stretch-prepared whole mounts of adult rat irides, a dense, well-organized plexus of neurofilament-positive nerves originating in the trigeminal ganglion can be visualized. Such a two-dimensional tissue preparation is well-suited for studies on sensory and autonomic nerve fiber growth. In the present study the growth capacity of such neurofilament-positive nerves has been studied immunohistochemically. In irides homologously transplanted to the anterior eye chamber of adult albino rats, the intrinsic neurofilament-positive network had almost completely disappeared 4 days postoperatively. In whole mounts of iris grafts after 15 days and 4 weeks in oculo a gradually increasing plexus of nerves was observed. After 3.5 months in oculo a dense, regular network of fluorescent fibers had formed in the iris grafts to the same magnitude as in situ. However, whereas large axon bundles constituted a prominent feature of the distribution of neurofilament-positive nerves in situ, only a few and relatively thin axon bundles were seen in the grafts. The growth capacity of the neurofilament-positive trigeminal nerves was also studied by grafting fetal trigeminal ganglia to the anterior eye chamber. As visualized in cryostat sections, trigeminal grafts contained a large number of strongly fluorescent perikarya and a high density of positive fibers after intraocular maturation. Such grafts readily innervated the host iris. In the area immediately adjacent to the grafts, thin, parallel, rather weakly fluorescent fibers radiated out from the ganglia. When mature trigeminal grafts with attached host iris were regrafted to the anterior eye chamber of adult animals for a few days, in order to remove the intrinsic host iris innervation, such irides showed outgrowing fibers, often organized in small axon bundles, at long distances from the ganglion graft. The present report shows that both mature and immature neurofilament-immunoreactive neurons are capable of innervating the iris. Furthermore, this ingrowth can occur both in the presence and absence of normal intrinsic neurofilament-positive nerve fibers.

Animals↗

PubMed1978

Effect of L-form Streptococcus pyogenes and of lipoteichoic acid on human cells in tissue culture.

These studies showed the destruction of growing primary and established human cell lines with a predilection for the group A streptococci by an L-form of Streptococcus pyogenes adapted to grow in isotonic media. Also, this L-form was detected by fluorescent antibody for longer periods of time than by viable count in infected but recovered tissue culture monolayers. Additional studies with human heart cells showed changes in their protein profile and fatty acid content (but not composition) after L-form infection. This report is the first to show that the morphological changes and death of human kidney cells by this viable L-form were mimicked by the structurally different lipoteichoic acids from this organism and its parental streptococcus. These lipoteichoic acids were also equally effective in preventing attachment of S. pyogenes to human cell monolayers, but their deacylation obviated these two activities. Finally, the attachment of the isotonic L-form, as well as the parental streptococcus, to growing human kidney cells suggested that a rigid cell wall is not a prerequisite for host attachment in vitro.

Cell Line↗

PubMed2001

In vitro culture and synchronous release of Sarcocystis neurona merozoites from host cells.

The growth of Sarcocystis neurona, isolate UCD1, in continuous culture was examined in 10 cell lines to identify growth conditions and methods for the preparation of parasites free of gross host cell contamination for molecular studies. The unpredictable, slow release of merozoites in most cell lines prompted development of a method to synchronously release the parasites from infected host cells. The calcium ionophore A23187 at a concentration of 1 microM was found to release intracellular merozoites with a 40 min treatment at 37 degrees C. The release of merozoites en masse from attached host cells allowed for the rapid collection of relatively pure parasites from the culture supernatant. This release of merozoites occurred in five different host cell lines. The ionophore-released parasites were highly infectious for host cells and appeared to be morphologically identical to naturally released merozoites, except that the treated merozoites had an increased number of micronemes when examined by electron microscopy. The ionophore did not enhance the release of sporozoites from sporocysts, but freezing in the presence of 5% DMSO released sporozoites that were infectious to bovine monocytes in in vitro culture.

Animals↗

PubMed1998

The site-specific recombination system of the Lactobacillus species bacteriophage A2 integrates in gram-positive and gram-negative bacteria.

The region of the bacteriophage A2 genome involved in site-specific recombination with the DNA of Lactobacillus spp. has been identified. Two orfs, transcribed from the same strand, have been found immediately upstream of the phage attachment site (attP). The orf adjacent to attP predicts a 385-amino-acid protein that presents significant similarity with site-specific recombinases of the integrase family. The other orf encodes a basic polypeptide of 76 amino acid residues. The junctions of the prophage with the genomes of its hosts have been determined, allowing the identification of the host attachment site (attB), which has a common 19-nucleotide core region with attP. The attB site is located at the 3' end of the transfer RNALeu gene (anticodon CAA). Nonreplicative plasmids containing the A2-specific recombination cassette integrate into different lactobacilli but also into unrelated Gram-positive bacteria such as Lactococcus lactis and even into Escherichia coli. In Lc. lactis, integration occurs in a previously unknown intergenic region, whereas in E. coli, it maps within the rrnD operon, 5' of rrsD gene. Comparison of the integration sites in the different hosts indicates that some flexibility is permitted in the attB sequence, since Lc. lactis and E. coli only share 13 and 11 nucleotides, respectively, with the 19-nucleotide core sequence of the lactobacilli.

Amino Acid Sequence↗

PubMed1985

Kronborgia pugettensis sp.nov. (Neorhabdocoela: Fecampiidae), an endoparasitic turbellarian infesting the shrimp Heptacarpus kincaidi (Rathbun), with notes on its life-history.

The morphology of Kronborgia pugettensis sp. nov., an endoparasite from the haemocoele of the caridean shrimp Heptacarpus kincaidi is described from specimens collected in the San Juan Island region of the western coast of North America. Members of this species are unisexual as are other members of the genus, but only females were found. An ootype and a type of accessory reproductive gland not known from other Kronborgia spp. are described, but they are probably present in other members of the genus. The life-history is similar to that of other Kronborgia spp. After the female reaches maturity, it emerges from the host and secretes a tubiform cocoon around itself and deposits its egg capsules within it. Embryogenesis lasts about 4 months. A free-swimming larva locates the new host, attaches to its exterior, and secretes a cyst around itself. It then penetrates through the exoskeleton to reach the haemocoele. K. pugettensis is easily distinguished from other members of the genus by the shape of the cocoon, type of host, and geographic distribution. This is the second species of fecampiid described from North America, but several undescribed species are known to exist from their cocoons.

Animals↗

PubMed1997

Chlamydia trachomatis glycosaminoglycan-dependent and independent attachment to eukaryotic cells.

Chlamydia trachomatis consists of two biovars, lymphogranuloma venereum (LGV) and trachoma, that differ in their infectivity in vivo and in vitro. Although addition of exogenous heparin or heparan sulfate in vitro effectively inhibits infectivity of both biovars and inhibits LGV biovar attachment to host cells, trachoma biovar attachment was only modestly inhibited (approximately 30%) by exogenous heparin. To dissect the relationship of heparin inhibition of attachment and infectivity, a heparan sulfate lyase (heparitinase) was used to treat organisms and evaluated for changes in attachment and infectivity. In contrast to heparitinase-treated LGV biovar organisms that lose their ability to attach and infect, treatment of trachoma biovar organisms with a concentration of heparitinase sufficient to reduce trachoma biovar infectivity by > 90%, only inhibited attachment to host cells by approximately 40%. Significantly, attachment could be fully restored for heparitinase-treated organisms of both biovars with exogenous heparan sulfate; however, the coating of the trachoma biovar organisms with heparan sulfate rendered the trachoma biovar similar to the phenotype of the LGV biovar by > 90% sensitivity to heparin inhibition of attachment. These data suggest that the LGV biovar used predominantly a heparin-inhibitable mechanism for attaching to host cells, whereas the trachoma biovar used a heparin-independent means in addition to a heparin-dependent mechanism to adhere to host cells. Once attached, the trachoma biovar, nevertheless, relied on the heparin-dependent pathway to enter host cells.

Animals↗

PubMed1988

Biology of African trypanosomes in the tsetse fly.

African trypanosomes present several features of interest to cell biologists. These include: a repressible single mitochondrion with a large mass of mitochondrial DNA, the kinetoplast; a special organelle, the glycosome, which houses the enzymes of the glycolytic chain; a surface coat of variable glycoprotein which enables the parasite to evade the mammalian host's immune response; and a unique flagellum-to-host attachment mechanism associated with novel cytoskeletal elements. Trypanosome development during the life cycle involves cyclical activation and repression of genes controlling these activities. Understanding the complexity of parasite development in the tsetse fly vector is especially challenging but may help to suggest new methods for the control of trypanosomiasis.

Animals↗

PubMed2004

Molecular characterisation of five trypsin-like peptidase transcripts from the salmon louse (Lepeophtheirus salmonis) intestine.

Four novel trypsin-like S1A peptidase transcripts (LsTryp2-5) from the marine parasitic copepod Lepeophtheirus salmonis were characterised based on analyses of 1918 expressed sequence tags from two adult female libraries. In addition, one previously described salmon louse trypsin, LsTryp1, has been further characterised. The five peptidases possessed all residues typically found in trypsins in correct sequence contexts. Interestingly, two cysteine residues, possibly involved in a disulphide bridge not previously reported in trypsins are conserved in all louse trypsin sequences. Phylogenetic analyses showed that the five louse peptidases form a monophyletic group with other crustacean trypsins (Brachyurin Ts). Quantitative PCR analyses demonstrated increased transcript levels from planktonic to early host-attached stages and from preadult to sexually mature adult stages. Furthermore, sex-specific differences in transcription regulation were found. In situ hybridisation demonstrated that all five trypsin-like peptidases are transcribed throughout the undifferentiated midgut, indicating a digestive function. The sequence characteristics, histological localisation and transcript regulation suggest that LsTryp1-4 encode typical digestive trypsins. LsTryp5, however, showed some sequence and regulatory peculiarities that rendered its function less clear. Our findings support earlier suggestions for the function of the midgut cells and suggest the existence of an additional undifferentiated cell-type.

Amino Acid Sequence↗

PubMed2000

Expansin message regulation in parasitic angiosperms: marking time in development.

Parasitic strategies are widely distributed across the angiosperms and are estimated to have evolved at least eight different times. Within the obligate hemiparasitic and holoparasitic members, elaborate strategies for host selection have emerged. Here, we demonstrate that in the parasitic Scrophulariceae Striga asiatica, for which signal-mediated host detection is critical, expansin mRNA provides a reliable and accurate downstream molecular marker for the transition to the parasitic mode. Three different expansin genes, saExp1, saExp2, and saExp3, are regulated by xenognostic quinones. saExp3 appears to function as a seedling expansin, and its mRNA is depleted within minutes after induction of the host attachment organ. saExp1 and saExp2 share less homology with the known expansins, and their transcripts accumulate linearly over a critical induction period. The regulation of these genes suggests that the resources for developmental commitment must accumulate to a defined threshold before commitment to organogenesis is terminal. When the induction signal is removed prematurely, the accumulated message decays with a time constant that correlates with the time required for additional signal exposures to reinduce parasitic development. These results suggest that sophisticated controls exist for the accumulation of the necessary components for terminal commitment to the parasitic mode. Furthermore, building on the redox dependence of the inducing signal, they suggest a model akin to a "molecular capacitor" for clocking organogenesis in S. asiatica.

Adenine↗

PubMed1993

Structural studies of the enveloped dsRNA bacteriophage phi 6 of Pseudomonas syringae by Raman spectroscopy. I. The virion and its membrane envelope.

We report and interpret the first Raman spectrum of a double-stranded RNA virus containing a membrane envelope. Spectra of the native bacteriophage phi 6 and of its isolated host-attachment (spike) protein and phospholipid-free core assembly were collected from aqueous solutions over a wide range of temperature. Comparison of the vibrational spectra by digital difference methods permits the following structural conclusions regarding molecular constituents of the fully assembled virion. (1) The double-stranded RNA, phospholipid and protein components of the phage exhibit Raman amplitudes in accordance with their biochemically determined compositions in the native virion (10, 20 and 70%, respectively). (2) alpha-Helix and irregular conformations are the dominant secondary structures in proteins of both the viral membrane and nucleocapsid. This represents a departure from previously examined icosahedral phage and plant viruses, which are dominated by beta-sheet structures. (3) The phospholipids of the viral membrane are liquid crystalline throughout the determined range of virus thermostability (0 to 40 degrees C). (4) The P3 spike protein of phi 6, which is anchored to, but not sequestered within the viral membrane, is largely alpha-helical (approximately 35%) and highly thermolabile. Denaturation of P3 at temperatures above 30 degrees C leads to appreciable loss (approximately 20%) of alpha-helix in favor of beta-strand structure, and alters significantly the environments of many aromatic side-chains. (5) The secondary structures of integral membrane proteins of phi 6 are overwhelmingly alpha-helical (approximately 70 to 80%) and also thermolabile. In contrast to P3, which exhibits aspartate and glutamate carboxyls in the ionized form (CO2-), the integral membrane proteins exhibit only protonated carboxyl groups (COOH). Treatment of phi 6 with butylated hydroxytoluene (BHT), which has been shown to remove the P3 spike protein, does not significantly perturb phospholipids and associated integral proteins of the viral membrane or structural proteins and packaged double-stranded RNA of the nucleocapsid. However, P3 subunits, which are recovered after BHT treatment, exhibit radically altered secondary and tertiary structures, including the loss of most subunit alpha-helices. Among the P3 side-chains affected by BHT treatment, we note a general trend toward greater hydrophilicity and greater solvent exposure of the aromatic residues Trp and Tyr. On the other hand, the cysteine sulfhydryl groups of the BHT-isolated P3 monomer are not solvent exposed and function as strong hydrogen-bond donors in the protein core.(ABSTRACT TRUNCATED AT 400 WORDS)

Bacteriophage phi 6↗

PubMed1998

Gross anatomy of the muscle systems of Fasciola hepatica as visualized by phalloidin-fluorescence and confocal microscopy.

Neuropeptides, biogenic amines and acetylcholine are expressed abundantly within the nervous systems of parasitic flatworms, and are particularly evident in the innervation of the musculature. Such associations have implicated the nervous system in locomotion, host attachment and reproductive co-ordination. Information on the muscle systems of parasitic flatworms is generally sparse, in particular those muscles associated with the reproductive system, intestinal tract and attachment apparatus. Also, the use of sectioned material has left description of the 3-dimensional organization of the musculature largely unrecorded. Using fluorescein isothiocyanate (FITC)-labelled phalloidin as a site-specific probe for filamentous actin, applied to whole-mount preparations of adult Fasciola hepatica and examined by confocal scanning laser microscopy, the present work reports on the organization of the major muscle systems in this trematode parasite. A highly regular array of outer circular, intermediate longitudinal and inner diagonal fibres distinguishes the body wall musculature, which is also involved in the development of both ventral and oral suckers. Circular fibres dominate the duct walls of the male and female reproductive systems, whereas the muscles of the intestinal tract have a somewhat diffuse arrangement of fibres. An understanding of the structural complexity of the muscle systems of parasitic flatworms is considered as fundamental to the interpretation of results from physiological experiments.

Actins↗

PubMed2005

A colonization factor links Vibrio cholerae environmental survival and human infection.

Many bacteria that cause diseases must be able to survive inside and outside the host. Attachment to and colonization of abiotic or biotic surfaces is a common mechanism by which various microorganisms enhance their ability to survive in diverse environments. Vibrio cholerae is a Gram-negative aquatic bacillus that is often found in the environment attached to the chitinous exoskeletons of zooplankton. It has been suggested that attachment to zooplankton enhances environmental survival of Vibrio spp., probably by providing both an abundant source of carbon and nitrogen and protection from numerous environmental challenges. On ingestion by humans, some serogroups of V. cholerae cause the diarrhoeal disease cholera. The pathophysiology of cholera is a result of the effects of cholera toxin on intestinal epithelial cells. For sufficient quantities of cholera toxin to reach the intestinal epithelium and to produce clinical symptoms, colonization of the small bowel must occur. Because most V. cholerae do not colonize humans, but all probably require strategies for survival in the environment, we considered that colonization factors selected for in the environment may be the same as those required for intestinal colonization of humans. In support of this hypothesis, here we have identified a single protein required for efficient intestinal colonization that mediates attachment to both zooplankton and human epithelial cells by binding to a sugar present on both surfaces.

Acetylglucosamine↗

PubMed2003

Effects of Helicobacter pylori CagA protein on the growth and survival of B lymphocytes, the origin of MALT lymphoma.

Helicobacter pylori (H. pylori) is a causative agent of gastrointestinal diseases such as atrophic gastritis and gastroduodenal ulcer. Infection of cagA-positive H. pylori is also associated with gastric carcinoma and gastric mucosa-associated lymphoid tissue (MALT) lymphoma. The cagA gene product CagA is directly injected into the bacteria-attached host cells via the bacterial type IV secretion system. The translocated CagA deregulates intracellular signaling pathways and thereby initiates pathogenesis. In this work, we examined the biological effects of CagA on B cells, from which MALT lymphoma arises. Ectopic expression of CagA in interleukin 3-dependent B cells inhibited cell proliferation by suppressing the JAK-STAT signaling. CagA was also capable of preventing hydroxyurea-induced B-cell apoptosis through inhibiting p53 accumulation. In contrast to the effects of CagA in gastric epithelial cells, the observed CagA activities in B cells were independent of its tyrosine phosphorylation. Our results indicate that CagA possesses both phosphorylation-dependent and -independent activities in mammalian cells and that biological impacts of CagA depend on cell-type context. As a result of B-cell growth inhibition, CagA may diminish anti-H. pylori immune responses. Furthermore, CagA may play a role in the development of MALT lymphoma by impairing p53-dependent apoptosis.

B-Lymphocytes↗