CD14-dependent internalization and metabolism of extracellular phosphatidylinositol by monocytes

Abstract

We report that membrane CD14 (mCD14), a cell surface receptor found principally on leukocytes, can mediate the uptake and metabolism of extracellular phosphatidylinositol (PtdIns). mCD14 facilitates PtdIns internalization, targeting it to intracellular sites where, following stimulation with a calcium ionophore, it can be acted upon by cytosolic phospholipase A2. The [14C]arachidonate released from mCD14-acquired [14C]arachidonyl-PtdIns is either esterified to triacylglycerol and retained in the cell or secreted as free arachidonate or leukotrienes. Although less than 10% of the arachidonate-derived lipids secreted from endogenous cellular stores are 5-lipoxygenase metabolites, over one-half of the secreted 14C-lipids derived from mCD14-acquired PtdIns are hydroxyeicosatetraenoic acids or leukotriene B4. mCD14 may allow these highly active blood cells to acquire and use extracellular PtdIns as a source of arachidonate for leukotriene synthesis.