Limits...
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.

Show MeSH

Related in: MedlinePlus

The E. scolopes juvenile light organ has a complex three-dimensional morphology. (Left) Diagram of the ventral surface of a juvenile animal. The organs of the animal, including the light organ (lo) and gills (g), are suspended in the center of the animal’s mantle (body) cavity and, in this view, are visible through the translucent ventral mantle. (Center) Enlargement of a bisected organ showing the external surface (left) and the internal crypt environment (right), where the bacterial symbionts reside. (Right) Depiction of the detailed anatomy of the three crypts of one side of the organ. a, arms; aa, anterior appendages; ac, antechambers; ce, ciliated epithelium; d, ducts; dc, deep crypts; e, eyes; fl, funnel; fn, fins; p, pores; t, tentacles.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3569863&req=5

fig1: The E. scolopes juvenile light organ has a complex three-dimensional morphology. (Left) Diagram of the ventral surface of a juvenile animal. The organs of the animal, including the light organ (lo) and gills (g), are suspended in the center of the animal’s mantle (body) cavity and, in this view, are visible through the translucent ventral mantle. (Center) Enlargement of a bisected organ showing the external surface (left) and the internal crypt environment (right), where the bacterial symbionts reside. (Right) Depiction of the detailed anatomy of the three crypts of one side of the organ. a, arms; aa, anterior appendages; ac, antechambers; ce, ciliated epithelium; d, ducts; dc, deep crypts; e, eyes; fl, funnel; fn, fins; p, pores; t, tentacles.

Mentions: V. fischeri is acquired from the environment in each host generation. Within 6 to 8 h of hatching, symbiont cells colonize the microvillous surfaces of epithelium-lined crypts of the juvenile host (Fig. 1) (for a review, see reference 5), a process that is potentiated by a juvenile-specific field of ciliated cells on the light organ surface (7). The bacteria irreversibly signal light organ morphogenesis at about 12 h following the onset of the association (9), one conspicuous feature of which is the apoptosis-driven regression of the ciliated epithelial surface (10). MAMPs of V. fischeri, specifically, lipopolysaccharide (LPS) and peptidoglycan (PGN) derivatives, act in synergy to promote the apoptotic program and light organ morphogenesis (1). The lipid A component of V. fischeri LPS signals the characteristic chromatin condensation of early-stage apoptosis (6), and the peptidoglycan monomer (tracheal cytotoxin [TCT]) signals late-stage apoptosis, which involves DNA fragmentation and nuclear loss of a host PRR, Euprymna scolopes peptidoglycan recognition protein 1 (EsPGRP1) (8). The completion of this developmental process, while irreversibly triggered at around 12 h, requires 4 to 5 days following initial contact of the host with V. fischeri (10). Another conspicuous feature of the symbiosis is a set of host and symbiont diel rhythms, which begin at the first dawn following the onset of the symbiosis, i.e., at about 12 h, and continue through the life of the animal. On a daily basis, the animals vent ~90% of the crypt contents into the environment each day at dawn and the bacterial symbionts regrow over the day to fill the crypt spaces (11–13). The nocturnal animal emerges at dusk from its diurnal resting place in the sand to use the luminescence of the dense population of symbionts as camouflage while it forages at night in the water column.


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)

The E. scolopes juvenile light organ has a complex three-dimensional morphology. (Left) Diagram of the ventral surface of a juvenile animal. The organs of the animal, including the light organ (lo) and gills (g), are suspended in the center of the animal’s mantle (body) cavity and, in this view, are visible through the translucent ventral mantle. (Center) Enlargement of a bisected organ showing the external surface (left) and the internal crypt environment (right), where the bacterial symbionts reside. (Right) Depiction of the detailed anatomy of the three crypts of one side of the organ. a, arms; aa, anterior appendages; ac, antechambers; ce, ciliated epithelium; d, ducts; dc, deep crypts; e, eyes; fl, funnel; fn, fins; p, pores; t, tentacles.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig1: The E. scolopes juvenile light organ has a complex three-dimensional morphology. (Left) Diagram of the ventral surface of a juvenile animal. The organs of the animal, including the light organ (lo) and gills (g), are suspended in the center of the animal’s mantle (body) cavity and, in this view, are visible through the translucent ventral mantle. (Center) Enlargement of a bisected organ showing the external surface (left) and the internal crypt environment (right), where the bacterial symbionts reside. (Right) Depiction of the detailed anatomy of the three crypts of one side of the organ. a, arms; aa, anterior appendages; ac, antechambers; ce, ciliated epithelium; d, ducts; dc, deep crypts; e, eyes; fl, funnel; fn, fins; p, pores; t, tentacles.
Mentions: V. fischeri is acquired from the environment in each host generation. Within 6 to 8 h of hatching, symbiont cells colonize the microvillous surfaces of epithelium-lined crypts of the juvenile host (Fig. 1) (for a review, see reference 5), a process that is potentiated by a juvenile-specific field of ciliated cells on the light organ surface (7). The bacteria irreversibly signal light organ morphogenesis at about 12 h following the onset of the association (9), one conspicuous feature of which is the apoptosis-driven regression of the ciliated epithelial surface (10). MAMPs of V. fischeri, specifically, lipopolysaccharide (LPS) and peptidoglycan (PGN) derivatives, act in synergy to promote the apoptotic program and light organ morphogenesis (1). The lipid A component of V. fischeri LPS signals the characteristic chromatin condensation of early-stage apoptosis (6), and the peptidoglycan monomer (tracheal cytotoxin [TCT]) signals late-stage apoptosis, which involves DNA fragmentation and nuclear loss of a host PRR, Euprymna scolopes peptidoglycan recognition protein 1 (EsPGRP1) (8). The completion of this developmental process, while irreversibly triggered at around 12 h, requires 4 to 5 days following initial contact of the host with V. fischeri (10). Another conspicuous feature of the symbiosis is a set of host and symbiont diel rhythms, which begin at the first dawn following the onset of the symbiosis, i.e., at about 12 h, and continue through the life of the animal. On a daily basis, the animals vent ~90% of the crypt contents into the environment each day at dawn and the bacterial symbionts regrow over the day to fill the crypt spaces (11–13). The nocturnal animal emerges at dusk from its diurnal resting place in the sand to use the luminescence of the dense population of symbionts as camouflage while it forages at night in the water column.

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