Legionella pneumophila translocated translation inhibitors are required for bacterial-induced host cell cycle arrest

Abstract

1 2 3 4 Legionella pneumophila translocated translation inhibitors are required for bacterial-5 induced host cell cycle arrest 2 3 2 Abstract 3 3The cell cycle machinery controls diverse cellular pathways and is tightly regulated. 4Misregulation of cell division plays a central role in the pathogenesis of many disease processes. 3 5 Various microbial pathogens interfere with the cell cycle machinery to promote host cell 3 6 colonization. Although cell cycle modulation is a common theme among pathogens, the role that 3 7 this interference plays in promoting diseases is unclear. Previously we demonstrated that the G 1 3 8 and G 2 /M phases of the host cell cycle are permissive for Legionella pneumophila replication, 3 9 while S phase provides a toxic environment for bacterial replication. In this study we show that 4 0 L. pneumophila avoids host S phase by blocking host DNA synthesis and preventing cell cycle 4 1 progression into S phase. Cell cycle arrest upon Legionella contact is dependent on the Icm/Dot 4 2 secretion system. In particular, we found that cell cycle arrest is dependent on the intact 4 3 enzymatic activity of translocated substrates that inhibits host translation. Moreover, we show 4 4 that early in infection, the presence of these translation inhibitors is crucial to induce the 4 5 degradation of the master regulator cyclin D1. Our results demonstrate that the bacterial effectors 4 6 that inhibit translation are associated with preventing entry of host cells into a phase associated 4 7 with restriction of L. pneumophila. Furthermore, control of cyclin D1 may be a common 4 8 strategy used by intracellular pathogens to manipulate the host cell cycle and promote bacterial 4 9

The L. pneumophila effector PieF modulates mRNA stability through association with eukaryotic CCR4-NOT

“…It has been shown that cytoplasmic localization of TOB was critical for its ability to inhibit cellular proliferation (127). L. pneumophila has been previously shown to actively arrest the host cell cycle in both mammalian, and protozoan cells through the activity of numerous effectors (47,(145)(146)(147), aiding the formation of a replication permissive compartment. During infection, it is imperative for the bacterium to block host entry into S-phase, as this cell cycle stage destabilizes the LCV and prevents bacterial replication (145).…”

“…The mechanisms that pathogens use to modulate host gene expression are diverse and pathogen-dependent (46). L. pneumophila utilizes at least eight pathogenic factors to interfere with host translation through diverse mechanisms to alter the cell cycle and influence immune signaling cascades (39, 47). The effectors Lgt1-3 can mono-glucosylate the GTPase domain of eukaryotic elongation factor eEF1A, impairing function and translational elongation (48, 49).…”

The Legionella pneumophila Dot/Icm type IV secretion system and its effectors

“…One of the consequences of this is the rapid loss of the cyclin D1, a key regulator of cell cycle transition from G1 to S phase, which arrests the cell cycle prior to entry into S phase [315]. This arrest facilitates intracellular replication, as transition would destabilize the LCV and cells in S phase are less conducive to infection [315,316]. This effect depends mainly on Lgt1 and Lgt3 and can be recapitulated by ectopic expression of the effectors.…”

“…This effect might be amplified by the increased ubiquitination and proteasomal degradation of proteins triggered by the bacteria. One of the consequences of this is the rapid loss of the cyclin D1, a key regulator of cell cycle transition from G1 to S phase, which arrests the cell cycle prior to entry into S phase [315]. This arrest facilitates intracellular replication, as transition would destabilize the LCV and cells in S phase are less conducive to infection [315,316].…”