Salmonella enterica is responsible for food poisoning and typhoid fever. Part of the pathological program induced by Salmonella involves the programmed cell death of macrophages. After infecting a macrophage, Salmonella use their type III secretion system to inject the cells with a protein, SipB, which eventually causes cell death. Hernandez et al. describe in detail how SipB induces cell death. When SipB alone was expressed in cultured cells, it induced the production of multilayered membrane structures reminiscent of autophagosomes, which are seen when the endoplasmic reticulum (ER) wraps around other organelles within the cell that are destined for degradation. Consistent with this, the SipB-induced structures contained markers for both ER and mitochondria, and, in Salmonella-infected macrophages, SipB was localized within disrupted mitochondria. Thus, it seems that Salmonella induces the death of these target cells by disrupting mitochondria and promoting autophagy. -- SMH
J. Cell Biol. 163, 1123 (2003).
