Disease relevance of plcA

• It seems that the plcA gene and its expression (in the PI-PLC assay) have an important role as virulence determinants in pathogenic Listeria spp [1].
• Expression of the plcA gene in Escherichia coli correlates with the appearance of PI-PLC activity in the cells [2].
• This 36 kDa protein is encoded by the gene plcA, and is homologous to the Bacillus cereus, Bacillus thuringiensis and eukaryotic phosphatidylinositol-specific phospholipases C (PI-PLC) [2].
• Phosphatidylinositol-specific phospholipase C of Bacillus anthracis down-modulates the immune response [3].
• Exotoxins such as listeriolysin (LLO) and phosphatidylinositol-specific phospholipase C (PIcA) have been implicated in listerial infection and sepsis [4].

High impact information on plcA

• Listeria monocytogenes phosphatidylinositol-specific phospholipase C has evolved for virulence by greatly reduced activity on GPI anchors [5].
• Listeria monocytogenes phosphatidylinositol-specific phospholipase C (PI-PLC) plays a critical role in escape of this human pathogen from host cell vacuoles [5].
• These data support a postulated accessory role for PI-PLC with LLO in lysing the primary phagosome of a macrophage [6].
• Large unilamellar vesicles, approximately 0.1 micron in diameter, encapsulating the fluorescent probe calcein, were treated with PI-PLC or LLO at pH 6.0, and each was capable of causing dye release [6].
• Thus, the effect of PI-PLC did not depend on lipid hydrolysis [6].

Chemical compound and disease context of plcA

• Expression of listeriolysin and phosphatidylinositol-specific phospholipase C is repressed by the plant-derived molecule cellobiose in Listeria monocytogenes [7].

Biological context of plcA

• Increased plcA transcript levels, which were similar in both host cell vacuole and cytosol, were associated with increases in both prfA expression and PrfA activity. qRT-PCR assays were designed to measure expression of prfA from each of its three promoter regions [8].
• PI-PLC activity was lost and virulence decreased when the plcA gene was disrupted in the chromosome [2].
• A plcA gene from L. monocytogenes was cloned downstream of a gram-positive promoter in the plasmid pWS2-2 [9].
• Although mutations in plcA or plcB resulted in small increases in mouse 50% lethal dose (LD50), deletions in both genes resulted in a 500-fold increase in LD50 [10].
• Derivatives of L. monocytogenes containing these specific plcA mutations were found to have phenotypes similar to that of the plcA deletion strain in an assay for escape from the primary vacuole, in intracellular growth in a murine macrophage cell line, and in a plaquing assay for cell-to-cell spread [11].

Anatomical context of plcA

• The remaining hemolytic L. monocytogenes isolates lacking the plcA gene and PI-PLC assay activity were, however, non-pathogenic via mice and chick-embryo inoculation tests, in spite of having the hlyA gene [12].
• The addition of this one gene, plcA, to a species of Listeria that in the wild-type state does not replicate intracellularly apparently can now allow some of the bacteria to transiently multiply inside the phagosomes of host macrophage cells [9].
• The plcA- mutant, but not the plcB- mutant, expressed an increase in susceptibility to the anti-listerial activity of macrophages [13].
• In vivo, L. monocytogenes plcA- mutant was found to be a more effective stimulator of T cells than the wild LO 28 strain [13].
• The listerial exotoxins listeriolysin and phosphatidylinositol-specific phospholipase C synergize to elicit endothelial cell phosphoinositide metabolism [4].

Associations of plcA with chemical compounds

• Although cellobiose represses expression of hly and plcA at the level of transcript accumulation, quantitative Western blot analysis indicates that cellobiose has no effect on PrfA levels [14].
• Computer modeling using QUANTA constrained by this NOE and ring coupling constants suggests that the inositol ring is nearly parallel to the chain packing direction, leaving the phosphate ester accessible to attack by phosphatidylinositol-specific phospholipase C enzymes [15].
• Gel filtration chromatography on Sephacryl S-200 in the presence of 1 M ammonium sulfate resulted in disaggregation and complete separation of PI-PLC, which interacted with the column matrix [16].

Analytical, diagnostic and therapeutic context of plcA

• The remaining three hemolytic but non-pathogenic L. monocytogenes isolates were negative for plcA by PCR [1].
• Gel retardation assays performed with a DNA fragment carrying the PrfA binding site of the plcA promoter demonstrated that the PrfA* mutant form is much more efficient than wild-type PrfA at forming specific DNA-protein complexes [17].
• These results could be corroborated by further comparative sequence analysis of genes encoding two phospholipases - plcA and plcB [18].
• A total of 125 serum samples were tested by phosphatidylinositol-specific phospholipase C (PIPLC) based indirect ELISA of which 4.0% turned out to be seropositive [19].

References