Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0023241 (Legionella)
 6,990 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To establish a vacuole that supports bacterial replication, Legionella pneumophila translocates a large number of bacterial proteins into host cells via the Dot/Icm type IV secretion system. Functions of most of these translocated proteins are unknown, but recent investigations suggest their roles in modulating diverse host processes such as vesicle trafficking, autophagy, ubiquitination, and apoptosis. Cells infected by L. pneumophila exhibited resistance to apoptotic stimuli, but the bacterial protein directly involved in this process remained elusive. We show here that SidF, one substrate of the Dot/Icm transporter, is involved in the inhibition of infected cells from undergoing apoptosis to allow maximal bacterial multiplication. Permissive macrophages harboring a replicating sidF mutant are more apoptotic and more sensitive to staurosporine-induced cell death. Furthermore, cells expressing SidF are resistant to apoptosis stimuli. SidF contributes to apoptosis resistance in L. pneumophila-infected cells by specifically interacting with and neutralizing the effects of BNIP3 and Bcl-rambo, two proapoptotic members of Bcl2 protein family. Thus, inhibiting the functions of host pro-death proteins by translocated effectors constitutes a mechanism for L. pneumophila to protect host cells from apoptosis.
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PMID:Legionella pneumophila inhibits macrophage apoptosis by targeting pro-death members of the Bcl2 protein family. 1736 Mar 63

The human pathogen Legionella pneumophila must evade host cell death signaling to enable replication in lung macrophages and to cause disease. After bacterial growth, however, L. pneumophila is thought to induce apoptosis during egress from macrophages. The bacterial effector protein, SidF, has been shown to control host cell survival and death by inhibiting pro-apoptotic BNIP3 and BCL-RAMBO signaling. Using live-cell imaging to follow the L. pneumophila-macrophage interaction, we now demonstrate that L. pneumophila evades host cell apoptosis independent of SidF. In the absence of SidF, L. pneumophila was able to replicate, cause loss of mitochondria membrane potential, kill macrophages, and establish infections in lungs of mice. Consistent with this, deletion of BNIP3 and BCL-RAMBO did not affect intracellular L. pneumophila replication, macrophage death rates, and in vivo bacterial virulence. Abrogating mitochondrial cell death by genetic deletion of the effectors of intrinsic apoptosis, BAX, and BAK, or the regulator of mitochondrial permeability transition pore formation, cyclophilin-D, did not affect bacterial growth or the initial killing of macrophages. Loss of BAX and BAK only marginally limited the ability of L. pneumophila to efficiently kill all macrophages over extended periods. L. pneumophila induced killing of macrophages was delayed in the absence of capsase-11 mediated pyroptosis. Together, our data demonstrate that L. pneumophila evades host cell death responses independently of SidF during replication and can induce pyroptosis to kill macrophages in a timely manner.
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PMID:Legionella pneumophila Strain 130b Evades Macrophage Cell Death Independent of the Effector SidF in the Absence of Flagellin. 2826 64