Legionella phosphatase hydrolyzes phosphatidylinositol 4,5-bisphosphate and inosital triphosphate in human neutrophils
Legionella are facultative intracellular bacterial pathogens which multiply in host phagocytes. L. micdadei cells contain an acid phosphatase (ACP) that blocks superoxide anion production by human neutrophils stimulated with the formylated peptide, fMLP. The possibility that ACP acts by interefering with polyphosphoinositide metabolism and the production of the intracellular second messenger, inositol triphosphate (IP3) was explored. When neutrophil phosphoinositides were labeled with TSP, incubation of the cells with ACP caused an 85% loss of the labeled phosphatidylinositol-4,5-bisphosphate (PIP2) over 2 h. Treatment of (TH)inositol-labeled neutrophils with ACP for 30 min resulted in a 20% decrease of labeled PIP2. Following fMLP stimulation, the fractional reduction in PIP2 and the fractional increase in IP3 was the same in ACP-treated and untreated neutrophils, but the total quantity of IP3 was reduced by ACP pre-treatment. The reduction in IP3 generated following fMLP stimulation seems to be due primarily to the decreased amount of PIP2 available for hydrolysis. However, some loss of IP3 due to direct hydrolysis by ACP cannot be ruled out. The Legionella phosphatase may compromise neutrophil response to the bacteria by hydrolyzing PIP2, the prognitor of IP3, and by hydrolyzing IP3 itself.
- Research Organization:
- Univ. of Pittsburgh, PA
- OSTI ID:
- 6285227
- Report Number(s):
- CONF-870644-; TRN: 87-028708
- Journal Information:
- Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States), Vol. 46:6; Conference: 78. annual meeting of the American Society of Biological Chemists conference, Philadelphia, PA, USA, 7 Jun 1987
- Country of Publication:
- United States
- Language:
- English
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550201* - Biochemistry- Tracer Techniques