The nature of the phagosomal membrane: endoplasmic reticulum versus plasmalemma

Abstract: For decades, the vacuole that sur-rounds particles engulfed by phagocytosis was be-lieved to originate from the plasma membrane. Conversion of the nascent phagosome into a micro-bicidal organelle was thought to result from the subsequent, orderly fusion of early endosomes, late endosomes, and ultimately, lysosomes with the original plasma membrane-derived vacuole. This conventional model has been challenged, if not superseded, by a revolutionary model that regards phagosome formation as resulting from the particle sliding into the endoplasmic reticulum via an open-ing at the base of the phagocytic cup. The merits and implications of these two hypotheses are sum-marized here and analyzed in light of recen