Suzanne E. Barbour، نويسنده , , Francine Marciano-Cabral، نويسنده ,

1601729

Naegleria fowleri amoebae express a membrane-associated calcium-independent phospholipase A2

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Naegleria fowleri, a free-living amoeba, is the causative agent of primary amoebic meningoencephalitis. Previous reports have demonstrated that N. fowleri expresses one or more forms of phospholipase A2 (PLA2) and that a secreted form of this enzyme is involved in pathogenesis. However, the molecular nature of these phospholipases remains largely unknown. This study was initiated to determine whether N. fowleri expresses analogs of the well-characterized PLA2s that are expressed by mammalian macrophages. Amoeba cell homogenates contain a PLA2 activity that hydrolyzes the substrate that is preferred by the 85 kDa calcium-dependent cytosolic PLA2, cPLA2. However, unlike the cPLA2 enzyme in macrophages, this activity is largely calcium-independent, is constitutively associated with membranes and shows only a modest preference for phospholipids that contain arachidonate. The amoeba PLA2 activity is sensitive to inhibitors that block the activities of cPLA2-α and the 80 kDa calcium-independent PLA2, iPLA2, that are expressed by mammalian cells. One of these compounds, methylarachidonyl fluorophosphonate, partially inhibits the constitutive release of [3H]arachidonic acid from pre-labeled amoebae. Together, these data suggest that N. fowleri expresses a constitutively active calcium-independent PLA2 that may play a role in the basal phospholipid metabolism of these cells

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phospholipase A2 , Amoeba , phospholipid , Naegleria fowleri , cPLA2 , pathogenesis

Studia Iranica

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