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Modulation of symbiont lipid A signaling by host alkaline phosphatases in the squid-vibrio symbiosis.

Rader BA, Kremer N, Apicella MA, Goldman WE, McFall-Ngai MJ - MBio (2012)

Bottom Line: With constant presentation of MAMPs by the normal microbiota, mechanisms to tolerate their effects have developed.The results of this contribution provide evidence that host alkaline phosphatases (APs) dephosphorylate and inactivate the symbiont MAMP lipid A.Not only may these activities serve to "tame" the MAMPs, but also the resulting products may themselves be important signals in persistent mutualisms.

View Article: PubMed Central - PubMed

Affiliation: Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, Wisconsin, USA.

ABSTRACT

Unlabelled: The synergistic activity of Vibrio fischeri lipid A and the peptidoglycan monomer (tracheal cytotoxin [TCT]) induces apoptosis in the superficial cells of the juvenile Euprymna scolopes light organ during the onset of the squid-vibrio symbiosis. Once the association is established in the epithelium-lined crypts of the light organ, the host degrades the symbiont's constitutively produced TCT by the amidase activity of a peptidoglycan recognition protein (E. scolopes peptidoglycan recognition protein 2 [EsPGRP2]). In the present study, we explored the role of alkaline phosphatases in transforming the lipid A of the symbiont into a form that changes its signaling properties to host tissues. We obtained full-length open reading frames for two E. scolopes alkaline phosphatase (EsAP) mRNAs (esap1 and esap2); transcript levels suggested that the dominant light organ isoform is EsAP1. Levels of total EsAP activity increased with symbiosis, but only after the lipid A-dependent morphogenetic induction at 12 h, and were regulated over the day-night cycle. Inhibition of total EsAP activity impaired normal colonization and persistence by the symbiont. EsAP activity localized to the internal regions of the symbiotic juvenile light organ, including the lumina of the crypt spaces where the symbiont resides. These data provide evidence that EsAPs work in concert with EsPGRPs to change the signaling properties of bacterial products and thereby promote persistent colonization by the mutualistic symbiont.

Importance: The potential for microbe-associated molecular patterns (MAMPs) to compromise host-tissue health is reflected in the often-used nomenclature for these molecules: lipopolysaccharide (LPS) is also called "endotoxin" and the peptidoglycan monomer is also called "tracheal cytotoxin" (TCT). With constant presentation of MAMPs by the normal microbiota, mechanisms to tolerate their effects have developed. The results of this contribution provide evidence that host alkaline phosphatases (APs) dephosphorylate and inactivate the symbiont MAMP lipid A. As such, APs work in synergy with a peptidoglycan recognition protein, which inactivates symbiont-exported TCT, to alter the symbiont MAMPs and promote persistence of the partnership. Not only may these activities serve to "tame" the MAMPs, but also the resulting products may themselves be important signals in persistent mutualisms. The finding of lipid A modification by APs in an invertebrate mutualism provides evidence that this specific strategy for dealing with symbiotic partners is conserved across the animal kingdom.

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Related in: MedlinePlus

pH optima of the light organ EsAPs. The values represent phosphate activity in the central core extracts relative to buffer pH. ◊, reactions in sodium acetate buffer (pKa, 4.76); ●, reactions in Tris-HCl buffer (pKa, 8.06); □, reactions in sodium carbonate buffer (pKa, 10.35). Bars indicate that standard errors are present, although some are too small to be distinguished from the data point; n = 5 technical replicates.
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fig5: pH optima of the light organ EsAPs. The values represent phosphate activity in the central core extracts relative to buffer pH. ◊, reactions in sodium acetate buffer (pKa, 4.76); ●, reactions in Tris-HCl buffer (pKa, 8.06); □, reactions in sodium carbonate buffer (pKa, 10.35). Bars indicate that standard errors are present, although some are too small to be distinguished from the data point; n = 5 technical replicates.

Mentions: We sought to determine the pH optimum of the putative AP activity in the light organ for two reasons: (i) to confirm that the observed activity is due to alkaline and not acid phosphatases and (ii) because diel fluctuations in crypt pH have been implicated in the control of the symbiosis (11). We pooled the extracted total soluble proteins from the light organ central cores of four adult animals and measured activity across a range from pH 3 to 11. A peak of activity occurred at pH 8.0, with activity decreasing with increasing acidity or alkalinity (Fig. 5). No activity peak at the lower pHs was detected, suggesting that the central core of the light organ has low or no acid phosphatase activity.


Modulation of symbiont lipid A signaling by host alkaline phosphatases in the squid-vibrio symbiosis.

Rader BA, Kremer N, Apicella MA, Goldman WE, McFall-Ngai MJ - MBio (2012)

pH optima of the light organ EsAPs. The values represent phosphate activity in the central core extracts relative to buffer pH. ◊, reactions in sodium acetate buffer (pKa, 4.76); ●, reactions in Tris-HCl buffer (pKa, 8.06); □, reactions in sodium carbonate buffer (pKa, 10.35). Bars indicate that standard errors are present, although some are too small to be distinguished from the data point; n = 5 technical replicates.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3569863&req=5

fig5: pH optima of the light organ EsAPs. The values represent phosphate activity in the central core extracts relative to buffer pH. ◊, reactions in sodium acetate buffer (pKa, 4.76); ●, reactions in Tris-HCl buffer (pKa, 8.06); □, reactions in sodium carbonate buffer (pKa, 10.35). Bars indicate that standard errors are present, although some are too small to be distinguished from the data point; n = 5 technical replicates.
Mentions: We sought to determine the pH optimum of the putative AP activity in the light organ for two reasons: (i) to confirm that the observed activity is due to alkaline and not acid phosphatases and (ii) because diel fluctuations in crypt pH have been implicated in the control of the symbiosis (11). We pooled the extracted total soluble proteins from the light organ central cores of four adult animals and measured activity across a range from pH 3 to 11. A peak of activity occurred at pH 8.0, with activity decreasing with increasing acidity or alkalinity (Fig. 5). No activity peak at the lower pHs was detected, suggesting that the central core of the light organ has low or no acid phosphatase activity.

Bottom Line: With constant presentation of MAMPs by the normal microbiota, mechanisms to tolerate their effects have developed.The results of this contribution provide evidence that host alkaline phosphatases (APs) dephosphorylate and inactivate the symbiont MAMP lipid A.Not only may these activities serve to "tame" the MAMPs, but also the resulting products may themselves be important signals in persistent mutualisms.

View Article: PubMed Central - PubMed

Affiliation: Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, Wisconsin, USA.

ABSTRACT

Unlabelled: The synergistic activity of Vibrio fischeri lipid A and the peptidoglycan monomer (tracheal cytotoxin [TCT]) induces apoptosis in the superficial cells of the juvenile Euprymna scolopes light organ during the onset of the squid-vibrio symbiosis. Once the association is established in the epithelium-lined crypts of the light organ, the host degrades the symbiont's constitutively produced TCT by the amidase activity of a peptidoglycan recognition protein (E. scolopes peptidoglycan recognition protein 2 [EsPGRP2]). In the present study, we explored the role of alkaline phosphatases in transforming the lipid A of the symbiont into a form that changes its signaling properties to host tissues. We obtained full-length open reading frames for two E. scolopes alkaline phosphatase (EsAP) mRNAs (esap1 and esap2); transcript levels suggested that the dominant light organ isoform is EsAP1. Levels of total EsAP activity increased with symbiosis, but only after the lipid A-dependent morphogenetic induction at 12 h, and were regulated over the day-night cycle. Inhibition of total EsAP activity impaired normal colonization and persistence by the symbiont. EsAP activity localized to the internal regions of the symbiotic juvenile light organ, including the lumina of the crypt spaces where the symbiont resides. These data provide evidence that EsAPs work in concert with EsPGRPs to change the signaling properties of bacterial products and thereby promote persistent colonization by the mutualistic symbiont.

Importance: The potential for microbe-associated molecular patterns (MAMPs) to compromise host-tissue health is reflected in the often-used nomenclature for these molecules: lipopolysaccharide (LPS) is also called "endotoxin" and the peptidoglycan monomer is also called "tracheal cytotoxin" (TCT). With constant presentation of MAMPs by the normal microbiota, mechanisms to tolerate their effects have developed. The results of this contribution provide evidence that host alkaline phosphatases (APs) dephosphorylate and inactivate the symbiont MAMP lipid A. As such, APs work in synergy with a peptidoglycan recognition protein, which inactivates symbiont-exported TCT, to alter the symbiont MAMPs and promote persistence of the partnership. Not only may these activities serve to "tame" the MAMPs, but also the resulting products may themselves be important signals in persistent mutualisms. The finding of lipid A modification by APs in an invertebrate mutualism provides evidence that this specific strategy for dealing with symbiotic partners is conserved across the animal kingdom.

Show MeSH
Related in: MedlinePlus