Physiological basis of the low calcium response in Yersinia pestis

Fowler, Janet M.; Brubaker, Robert R.

doi:10.1128/iai.62.12.5234-5241.1994

Cited by 62 publications

(35 citation statements)

References 53 publications

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“…Under these conditions, there is high-level Yop expression and secretion accompanied by cessation of bacterial growth (referred to as growth restriction), collectively termed the low-Ca 2ϩ response (LCR) (52). Growth restriction probably does not occur in vivo (17) but has been a useful marker of Yop induction (51).…”

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confidence: 99%

YscP of Yersinia pestis Is a Secreted Component of the Yop Secretion System

Payne

Straley

1999

J Bacteriol

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The Yersinia pestis low-Ca2+ response stimulon is responsible for the environmentally regulated expression and secretion of antihost proteins (V antigen and Yops). We have previously shown that yscO encodes a secreted core component of the Yop secretion (Ysc) mechanism. In this study, we constructed and characterized in-frame deletions in the adjacent gene,yscP, in the yscN–yscU operon. The ΔP1 mutation, which removed amino acids 246 to 333 of YscP, had no effect on Yop expression or secretion, and the mutant protein, YscP1, was secreted, as was YscP in the parent. In contrast, the ΔP2 strain expressed and secreted less of each Yop than did the parent under the inductive conditions of 37°C and the absence of Ca2+, with an exception being YopE, which was only minimally affected by the mutation. The YscP2 protein, missing amino acids 57 to 324 of YscP, was expressed but not secreted by the ΔP2 mutant. The effect of the ΔP2 mutation was at the level of Yop secretion because YopM and V antigen still showed limited secretion when overproduced in trans. Excess YscP also affected secretion: overexpression of YscP in the parent, in either yscP mutant, or in an lcrGmutant effectively shut off secretion. However, co-overexpression of YscO and YscP had no effect on secretion, and YscP overexpression in anlcrE mutant had little effect on Yop secretion, suggesting that YscP acts, in conjunction with YscO, at the level of secretion control of LcrE at the bacterial surface. These findings place YscP among the growing family of mobile Ysc components that both affect secretion and themselves are secreted by the Ysc.

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confidence: 99%

YscP of Yersinia pestis Is a Secreted Component of the Yop Secretion System

Payne

Straley

1999

J Bacteriol

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“…If Ca 2ϩ is present, the yersiniae grow normally (without restriction). This growth component of the LCR likely is an in vitro phenomenon (10) and is not known to occur in vivo, but it is a useful marker for the degree of LCR induction in in vitro studies. The absence of Ca 2ϩ appears to mimic an unidentified signal that yersiniae receive when they are adherent to a eukaryotic cell, except that the resulting secretion is localized to the site of contact between the bacterium and the cell (27).…”

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The V Antigen of Yersinia pestis Regulates Yop Vectorial Targeting as Well as Yop Secretion through Effects on YopB and LcrG

1998

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Yersinia pestis expresses a set of secreted proteins called Yops and the bifunctional LcrV, which has both regulatory and antihost functions. Yops and LcrV expression and the activity of the type III mechanism for their secretion are coordinately regulated by environmental signals such as Ca2+ concentration and eukaryotic cell contact. In vitro, Yops and LcrV are secreted into the culture medium in the absence of Ca2+ as part of the low-Ca2+ response (LCR). The LCR is induced in a tissue culture model by contact with eukaryotic cells that results in Yop translocation into cells and subsequent cytotoxicity. The secretion mechanism is believed to indirectly regulate expression oflcrV and yop operons by controlling the intracellular concentration of a secreted negative regulator. LcrG, a secretion-regulatory protein, is thought to block secretion of Yops and LcrV, possibly at the inner face of the inner membrane. A recent model proposes that when the LCR is induced, the increased expression of LcrV yields an excess of LcrV relative to LcrG, and this is sufficient for LcrV to bind LcrG and unblock secretion. To test this LcrG titration model, LcrG and LcrV were expressed alone or together in a newly constructed lcrG deletion strain, a ΔlcrG2mutant, of Y. pestis that produces low levels of LcrV and constitutively expresses and secretes Yops. Overexpression of LcrG in this mutant background was able to block secretion and depress expression of Yops in the presence of Ca2+ and to dramatically decrease Yop expression and secretion in growth medium lacking Ca2+. Overexpression of both LcrG and LcrV in the ΔlcrG2 strain restored wild-type levels of Yop expression and Ca2+ control of Yop secretion. Surprisingly, when HeLa cells were infected with the ΔlcrG2 strain, no cytotoxicity was apparent and translocation of Yops was abolished. This correlated with an altered distribution of YopB as measured by accessibility to trypsin. These effects were not due to the absence of LcrG, because they were alleviated by restoration of LcrV expression and secretion alone. LcrV itself was found to enter HeLa cells in a nonpolarized manner. These studies supported the LcrG titration model of LcrV’s regulatory effect at the level of Yop secretion and revealed a further role of LcrV in the deployment of YopB, which in turn is essential for the vectorial translocation of Yops into eukaryotic cells.

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“…The LCR is believed to be manifest in vivo upon yersinial contact with a eukaryotic cell (14). It is believed that growth restriction does not occur in vivo (23) but that Yops and V antigen expression and secretion are regulated and that the absence of Ca 2ϩ in vitro mimics cell contact (14,73). The genes that are coordinately downregulated (73) by Ca 2ϩ are referred to as the LCRS (low-Ca 2ϩ response stimulon) (72).…”

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YscO of Yersinia pestis Is a Mobile Core Component of the Yop Secretion System

Payne

Straley

1998

J Bacteriol

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The Yersinia pestis low-Ca2+ response stimulon is responsible for the temperature- and Ca2+-regulated expression and secretion of plasmid pCD1-encoded antihost proteins (V antigen and Yops). We have previously shown that lcrD, yscC, yscD,yscG, and yscR encode proteins that are essential for high-level expression and secretion of V antigen and Yops at 37°C in the absence of Ca2+. In this study, we characterized yscO of the Yop secretion (ysc) operon that contains yscN through yscU by determining the localization of its gene product and the phenotype of an in-frame deletion. The yscO mutant grew and expressed the same levels of Yops as the parent at 37°C in the presence of Ca2+. In the absence of Ca2+, the mutant grew independently of Ca2+, expressed only basal levels of V antigen and Yops, and failed to secrete these. These defects could be partially complemented by providing yscO intrans in the yscO mutant. Overexpression of YopM and V antigen in the mutant failed to restore the export of either protein, showing that the mutation had a direct effect on secretion. These results indicated that the yscO gene product is required for high-level expression and secretion of V antigen and Yops. YscO was found by immunoblot analysis in the soluble and membrane fractions of bacteria growing at 37°C irrespective of the presence of Ca2+ and in the culture medium in the absence of Ca2+. YscO is the only mobile protein identified so far in the Yersinia species that is required for secretion of V antigen and Yops.

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Physiological basis of the low calcium response in Yersinia pestis

Cited by 62 publications

References 53 publications

YscP of Yersinia pestis Is a Secreted Component of the Yop Secretion System

YscP of Yersinia pestis Is a Secreted Component of the Yop Secretion System

The V Antigen of Yersinia pestis Regulates Yop Vectorial Targeting as Well as Yop Secretion through Effects on YopB and LcrG

YscO of Yersinia pestis Is a Mobile Core Component of the Yop Secretion System

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