Proteomic Characterization of the Whole Secretome of Legionella pneumophila and Functional Analysis of Outer Membrane Vesicles

Abstract

Secretion of effector molecules is one of the major mechanisms by which the intracellular human pathogen

Life Stage-specific Proteomes of Legionella pneumophila Reveal a Highly Differential Abundance of Virulence-associated Dot/Icm effectors

“…Seventy percent of our quantified extracellular proteome (54 of 77 proteins) is covered by the secretome data of Galka et al, which is a reasonable overlap and therefore, presence of nonclassically secreted proteins may at least in part be explained by budded outer membrane vesicles. Indeed, eight of the extr in our study which were predicted as periplasmic or membranebound were previously identified in outer membrane vesicles (28). Moreover, six of the predicted 14 cytoplasmic, seven of the 11 predicted membrane, and 14 of the 21 predicted periplasmic proteins in our study were previously identified as L. pneumophila extracellular proteins (28).…”

“…Nevertheless, the here presented extracellular proteome contained a subset of proteins which, based on predictions, were unlikely candidates for classic secretion. However, L. pneumophila is known to shed outer membrane vesicles from intact membranes during intra-and extracellular growth (28). The study by Galka et al analyzed proteins found in outer membrane vesicles expelled by L. pneumophila and culture supernatants devoid of them (28).…”

“…However, L. pneumophila is known to shed outer membrane vesicles from intact membranes during intra-and extracellular growth (28). The study by Galka et al analyzed proteins found in outer membrane vesicles expelled by L. pneumophila and culture supernatants devoid of them (28). Seventy percent of our quantified extracellular proteome (54 of 77 proteins) is covered by the secretome data of Galka et al, which is a reasonable overlap and therefore, presence of nonclassically secreted proteins may at least in part be explained by budded outer membrane vesicles.…”

“…Previous proteomics studies gave an insight into the variety of L. pneumophila proteins present in the culture supernatant and on their dependence on type II secretion, Tat secretion, or export via outer membrane vesicles. In those studies, 2DE/MS analysis was used and identified at least 20 type II-secreted proteins, 20 proteins with differential abundance in wild type and a Tat mutant as well as 181 culture supernatant proteins of which 33 specifically were associated with outer membrane vesicles (20,(25)(26)(27)(28). Furthermore, in a recent study by Hoffmann et al, the proteome of intracellular L. pneumophila 1h post infection was analyzed by means of 1D gel electrophoresis and subsequent liquid chromatography-MS/MS (29).…”

The novel Legionella pneumophila type II secretion substrate NttC contributes to infection of amoebae Hartmannella vermiformis and Willaertia magna

“…T2S substrates move across the inner membrane via the Sec or Tat pathway and then a pseudopilus acts to push the proteins through an outer membrane pore (Korotkov et al, 2012). Based upon examination of the virulent strain 130b, L. pneumophila T2S exports ¢25 proteins, including 18 confirmed enzymes (Cianciotto, 2009;DebRoy et al, 2006a, b;Galka et al, 2008;Herrmann et al, 2011;Pearce & Cianciotto, 2009;Tyson et al, 2013). L. pneumophila mutants lacking the T2S apparatus are greatly impaired for infection of Acanthamoeba castellanii, Hartmannella vermiformis and Naegleria lovaniensis (Hales & Shuman, 1999;Liles et al, 1999;Polesky et al, 2001;Rossier & Cianciotto, 2001, 2005Rossier et al, 2004Rossier et al, , 2008Tyson et al, 2013).…”