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Modulation of Rab GTPase function by a protein phosphocholine transferase.
Nature. 2011 Sep 1; 477(7362):103-6
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18 Aug 2011
Drusilla Burns
F1000 Microbiology
Center for Biologics Evaluation and Research (CBER), Food and Drug Administration,
Rockville, MD, USA.
F1000 Microbiology
Center for Biologics Evaluation and Research (CBER), Food and Drug Administration,
Rockville, MD, USA.
New Finding
DOI: 10.3410/f.12700956.13962054
Bacterial effector proteins modulate host cells often by chemically modifying host cell proteins. In this noteworthy report, the authors describe a novel modification of the host cell GTPase Rab1 protein by the Legionella pneumophila effector protein AnkX.
Using cytidine diphosphocholine (CDP-choline)...Continue reading
Using cytidine diphosphocholine (CDP-choline)...Continue reading
Bacterial effector proteins modulate host cells often by chemically modifying host cell proteins. In this noteworthy report, the authors describe a novel modification of the host cell GTPase Rab1 protein by the Legionella pneumophila effector protein AnkX.
Using cytidine diphosphocholine (CDP-choline) as a substrate, AnkX covalently attaches a phosphocholine residue to Ser79 of Rab1. During infection, both Rab1 and Rab35 are modified by AnkX, resulting in an alteration of membrane transport. These results elucidate a novel mechanism by which bacterial effector proteins alter host cell function.
Using cytidine diphosphocholine (CDP-choline) as a substrate, AnkX covalently attaches a phosphocholine residue to Ser79 of Rab1. During infection, both Rab1 and Rab35 are modified by AnkX, resulting in an alteration of membrane transport. These results elucidate a novel mechanism by which bacterial effector proteins alter host cell function.
Disclosures
None declared
Add Comment
Burns D: F1000Prime Recommendation of [Mukherjee S et al., Nature 2011, 477(7362):103-6]. In F1000Prime, 18 Aug 2011; DOI: 10.3410/f.12700956.13962054. F1000Prime.com/12700956#eval13962054
30 Aug 2011
New Finding
DOI: 10.3410/f.12700956.14303055
Small GTPase proteins are frequently post-translationally modified by bacterial pathogens which manipulate the host cell to promote their own survival and replication. Mukherjee et al. have identified 'phosphocholination' as a new post-translational modification by which the Legionella pneumophila toxin...Continue reading
Small GTPase proteins are frequently post-translationally modified by bacterial pathogens which manipulate the host cell to promote their own survival and replication. Mukherjee et al. have identified 'phosphocholination' as a new post-translational modification by which the Legionella pneumophila toxin AnkX targets a switch II residue of Rab1.
L. pneumophila secretes a number of proteins into the host cell to promote formation of a compartment in which they can replicate (the Legionella-containing vacuole [LCV]). One of these proteins, SidM (also called DrrA), activates Rab1 through a C-terminal guanine nucleotide exchange factor (GEF) domain {1}. Furthermore, SidM prevents Rab1 from being inactivated by GTPase-activating proteins (GAPs) by adding adenosine monophosphate (AMPylation) to Tyr 77, which is catalyzed by an N-terminal domain {2}. Using mass spectrometry, Mukherjee et al. confirmed the presence of AMPylated Rab1 in vivo during L. pneumophila infection but also observed a previously unknown 183Da post-translational modification in the same region, which they identified as addition of a phosphocholine moiety to the Ser residue adjacent to the AMPylation site (Ser 76 in Rab1B, Ser 79 in Rab1A).
AnkX contains an FIC domain, which is usually associated with AMPylation, so it will be interesting to see structure-function analyses of the substrate specificity and catalytic mechanism of AnkX compared to other FIC domains. Phosphocholinated proteins have been observed in mammalian cells previously; thus, it will be interesting to determine whether, like AMPylation, phosphocholination is an endogenous post-translational modification used by eukaryotes. If so, it will be important to identify the mammalian enzymes responsible for this activity, as well as the protein substrates.
L. pneumophila secretes a number of proteins into the host cell to promote formation of a compartment in which they can replicate (the Legionella-containing vacuole [LCV]). One of these proteins, SidM (also called DrrA), activates Rab1 through a C-terminal guanine nucleotide exchange factor (GEF) domain {1}. Furthermore, SidM prevents Rab1 from being inactivated by GTPase-activating proteins (GAPs) by adding adenosine monophosphate (AMPylation) to Tyr 77, which is catalyzed by an N-terminal domain {2}. Using mass spectrometry, Mukherjee et al. confirmed the presence of AMPylated Rab1 in vivo during L. pneumophila infection but also observed a previously unknown 183Da post-translational modification in the same region, which they identified as addition of a phosphocholine moiety to the Ser residue adjacent to the AMPylation site (Ser 76 in Rab1B, Ser 79 in Rab1A).
AnkX contains an FIC domain, which is usually associated with AMPylation, so it will be interesting to see structure-function analyses of the substrate specificity and catalytic mechanism of AnkX compared to other FIC domains. Phosphocholinated proteins have been observed in mammalian cells previously; thus, it will be interesting to determine whether, like AMPylation, phosphocholination is an endogenous post-translational modification used by eukaryotes. If so, it will be important to identify the mammalian enzymes responsible for this activity, as well as the protein substrates.
References
Disclosures
None declared
Ikura M and Marshall C: F1000Prime Recommendation of [Mukherjee S et al., Nature 2011, 477(7362):103-6]. In F1000Prime, 30 Aug 2011; DOI: 10.3410/f.12700956.14303055. F1000Prime.com/12700956#eval14303055
30 Aug 2011
New Finding
DOI: 10.3410/f.12700956.14261055
This study reports the fascinating discovery that the Legionella effector AnkX has acylation activity, mediating the covalent addition of a phosphocholine group to serine 79 of Rab1.
Interestingly Ser79 is located near the tyrosine that is the site of another posttranslational modification (PTM) -- the...Continue reading
Interestingly Ser79 is located near the tyrosine that is the site of another posttranslational modification (PTM) -- the...Continue reading
This study reports the fascinating discovery that the Legionella effector AnkX has acylation activity, mediating the covalent addition of a phosphocholine group to serine 79 of Rab1.
Interestingly Ser79 is located near the tyrosine that is the site of another posttranslational modification (PTM) -- the addition of an AMP group. AnkX uses cytidine diphosphate choline (CDP-choline) as a substrate for the transfer of a phosphocholine group to Rab1 and can also act on the Rab1 family member Rab35. The cellular disruption mediated by AnkX requires the phosphocholine transfer activity of AnkX; however, when Ser79 in Rab1 is mutated to alanine, the secretion of alkaline phosphatase is also disrupted. Phosphocholination of Rab35 can disrupt its ability to interact with its exchange factor connecdenn, suggesting one possible mechanism for this PTM to block Rab activity.
Interestingly Ser79 is located near the tyrosine that is the site of another posttranslational modification (PTM) -- the addition of an AMP group. AnkX uses cytidine diphosphate choline (CDP-choline) as a substrate for the transfer of a phosphocholine group to Rab1 and can also act on the Rab1 family member Rab35. The cellular disruption mediated by AnkX requires the phosphocholine transfer activity of AnkX; however, when Ser79 in Rab1 is mutated to alanine, the secretion of alkaline phosphatase is also disrupted. Phosphocholination of Rab35 can disrupt its ability to interact with its exchange factor connecdenn, suggesting one possible mechanism for this PTM to block Rab activity.
Disclosures
None declared
Collins R: F1000Prime Recommendation of [Mukherjee S et al., Nature 2011, 477(7362):103-6]. In F1000Prime, 30 Aug 2011; DOI: 10.3410/f.12700956.14261055. F1000Prime.com/12700956#eval14261055
13 Sep 2011
New Finding
DOI: 10.3410/f.12700956.14480054
This paper reports the first example of post-translational modification of a protein by attachment of phosphocholine. The pathogen Legionella contains an enzyme that attaches phosphocholine to a Rab GTPase in its host cell. This modification affects membrane transport processes in the host cell involving...Continue reading
This paper reports the first example of post-translational modification of a protein by attachment of phosphocholine. The pathogen Legionella contains an enzyme that attaches phosphocholine to a Rab GTPase in its host cell. This modification affects membrane transport processes in the host cell involving Rab-1.
Disclosures
None declared
Gelb M: F1000Prime Recommendation of [Mukherjee S et al., Nature 2011, 477(7362):103-6]. In F1000Prime, 13 Sep 2011; DOI: 10.3410/f.12700956.14480054. F1000Prime.com/12700956#eval14480054
F1000Prime Recommendations, Dissents and Comments for [Mukherjee S et al., Nature 2011, 477(7362):103-6]. In F1000Prime, 23 May 2013; F1000Prime.com/12700956
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The intracellular pathogen Legionella pneumophila modulates the activity of host GTPases to direct the transport and assembly of the membrane-bound compartment in which it resides. In vitro studies have indicated that the Legionella protein DrrA post-translationally modifies the GTPase Rab1 by a process called AMPylation. Here we used mass spectrometry to investigate post-translational modifications to Rab1 that occur during infection of host cells by Legionella. Consistent with in vitro studies, DrrA-mediated AMPylation of a conserved tyrosine residue in the switch II region of Rab1 was detected during infection. In addition, a modification to an adjacent serine residue in Rab1 was discovered, which was independent of DrrA. The Legionella effector protein AnkX was required for this modification. Biochemical studies determined that AnkX directly mediates the covalent attachment of a phosphocholine moiety to Rab1. This phosphocholine transferase activity used CDP-choline as a substrate and required a conserved histidine residue located in the FIC domain of the AnkX protein. During infection, AnkX modified both Rab1 and Rab35, which explains how this protein modulates membrane transport through both the endocytic and exocytic pathways of the host cell. Thus, phosphocholination of Rab GTPases represents a mechanism by which bacterial FIC-domain-containing proteins can alter host-cell functions.
DOI: 10.1038/nature10335
PMID: 21822290
