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Acanthamoeba castellanii STAT protein.

Kicinska A, Leluk J, Jarmuszkiewicz W - PLoS ONE (2014)

Bottom Line: A. castellanii is the only, studied to date, Amoebozoan that does not belong to Mycetozoa but possesses STATs.The A. castellanii STAT protein branches next to a group of STATc proteins from Mycetozoa.We also demonstrate that Amoebozoa form a distinct monophyletic lineage within the STAT protein world that is well separated from the other groups.

View Article: PubMed Central - PubMed

Affiliation: Department of Bioenergetics, Adam Mickiewicz University, Poznan, Poland.

ABSTRACT
STAT (signal transducers and activators of transcription) proteins are one of the important mediators of phosphotyrosine-regulated signaling in metazoan cells. We described the presence of STAT protein in a unicellular, free-living amoebae with a simple life cycle, Acanthamoeba castellanii. A. castellanii is the only, studied to date, Amoebozoan that does not belong to Mycetozoa but possesses STATs. A sequence of the A. castellanii STAT protein includes domains similar to those of the Dictyostelium STAT proteins: a coiled coil (characteristic for Dictyostelium STAT coiled coil), a STAT DNA-binding domain and a Src-homology domain. The search for protein sequences homologous to A. castellanii STAT revealed 17 additional sequences from lower eukaryotes. Interestingly, all of these sequences come from Amoebozoa organisms that belong to either Mycetozoa (slime molds) or Centramoebida. We showed that there are four separated clades within the slime mold STAT proteins. The A. castellanii STAT protein branches next to a group of STATc proteins from Mycetozoa. We also demonstrate that Amoebozoa form a distinct monophyletic lineage within the STAT protein world that is well separated from the other groups.

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Phylogenetic relationship of the Amoebozoa STAT proteins.The results were obtained with the aid of MEGA 5.
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pone-0111345-g003: Phylogenetic relationship of the Amoebozoa STAT proteins.The results were obtained with the aid of MEGA 5.

Mentions: As expected, the N-terminal fragment shows a very high variability and no significant identity/similarity among the compared organisms. However, the rest of the sequences show a significant degree of conservativity/similarity (especially the C-terminal part), which is sufficient proof that they are homologous and that phylograms may be constructed for them. It is obvious that similarities are predominant in structurally important regions, i.e., in domains of a putative Dictyostelium coiled coil, the STAT DNA-binding domain, the linker domain that contains an EF-hand motif and the SH2 domain. All of these proteins have a conservative Y residue (number 1321 in the alignment, Figure S1). Previous studies show that A. castellanii SH2-containing proteins generally have unique domain combinations that are similar to those found in Dictyostelium[30]. The construction of phylogenetic trees using lower eukaryotic sequences and various tools led to the generation of various trees with respect to tree topology and branch distance length, depending on the applied method of analysis (Figures 3 and S2). It has been shown previously that it is favorable to use several methods of phylogenetic analysis for better reliability [35]. However, all of these methods indicate that there are four separated clades within the slime mold STAT proteins. All trees grouped the studied sequences from D. discoideum, D. fasciculatum, D. purpureum and P. pallidum into four groups. Moreover, all of these organisms seem to have exactly four STAT proteins that show a very close evolutionary relationship to one of the D. discoideum STATs (STATa, STATb, STATc or STATd). Only a STATb analog has not yet been found in D. purpureum. These observations suggest that the Dictyostelids' STAT repertoire was completed before the speciation of these slime mold species. The A. castellanii STAT protein branches next to a group of STATc proteins from slime molds. The other two sequences from A. castellanii seem to be more distantly related to the slime mold clades. It is especially interesting that no STATs have been found in any of the other Mycetozoa groups or in any other species that belongs to Amoebozoa. The open question remains what is the role of STAT proteins in A. castellanii. It has been previously shown that in STAT proteins in D. discoideum play a role in several aspects of differentiation. Extracellular cAMP signaling activates STATa, which can function as either a repressor or an activator of specific gene expressions [36]. At the D. discoideum slug stage, STATc in one of the prestalk cell subtypes, pstO cells, that prevents the expression of a marker of pstA cell differentiation [37]. However, it has also been reported that STATc accumulates in the nucleus rapidly when slime mold cells are subjected to hyperosmotic stress [38]. Therefore, STATc seems to be a key regulator of the transcriptional response to hyperosmotic shock [39]. Approximately 20% of the differentially regulated genes in D. discoideum cells treated with 200 mM sorbitol were dependent on the presence of STATc. The stress response could possibly be the answer to the question of why the simple unicellular amoeba A. castellanii needs STAT signaling.


Acanthamoeba castellanii STAT protein.

Kicinska A, Leluk J, Jarmuszkiewicz W - PLoS ONE (2014)

Phylogenetic relationship of the Amoebozoa STAT proteins.The results were obtained with the aid of MEGA 5.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4206453&req=5

pone-0111345-g003: Phylogenetic relationship of the Amoebozoa STAT proteins.The results were obtained with the aid of MEGA 5.
Mentions: As expected, the N-terminal fragment shows a very high variability and no significant identity/similarity among the compared organisms. However, the rest of the sequences show a significant degree of conservativity/similarity (especially the C-terminal part), which is sufficient proof that they are homologous and that phylograms may be constructed for them. It is obvious that similarities are predominant in structurally important regions, i.e., in domains of a putative Dictyostelium coiled coil, the STAT DNA-binding domain, the linker domain that contains an EF-hand motif and the SH2 domain. All of these proteins have a conservative Y residue (number 1321 in the alignment, Figure S1). Previous studies show that A. castellanii SH2-containing proteins generally have unique domain combinations that are similar to those found in Dictyostelium[30]. The construction of phylogenetic trees using lower eukaryotic sequences and various tools led to the generation of various trees with respect to tree topology and branch distance length, depending on the applied method of analysis (Figures 3 and S2). It has been shown previously that it is favorable to use several methods of phylogenetic analysis for better reliability [35]. However, all of these methods indicate that there are four separated clades within the slime mold STAT proteins. All trees grouped the studied sequences from D. discoideum, D. fasciculatum, D. purpureum and P. pallidum into four groups. Moreover, all of these organisms seem to have exactly four STAT proteins that show a very close evolutionary relationship to one of the D. discoideum STATs (STATa, STATb, STATc or STATd). Only a STATb analog has not yet been found in D. purpureum. These observations suggest that the Dictyostelids' STAT repertoire was completed before the speciation of these slime mold species. The A. castellanii STAT protein branches next to a group of STATc proteins from slime molds. The other two sequences from A. castellanii seem to be more distantly related to the slime mold clades. It is especially interesting that no STATs have been found in any of the other Mycetozoa groups or in any other species that belongs to Amoebozoa. The open question remains what is the role of STAT proteins in A. castellanii. It has been previously shown that in STAT proteins in D. discoideum play a role in several aspects of differentiation. Extracellular cAMP signaling activates STATa, which can function as either a repressor or an activator of specific gene expressions [36]. At the D. discoideum slug stage, STATc in one of the prestalk cell subtypes, pstO cells, that prevents the expression of a marker of pstA cell differentiation [37]. However, it has also been reported that STATc accumulates in the nucleus rapidly when slime mold cells are subjected to hyperosmotic stress [38]. Therefore, STATc seems to be a key regulator of the transcriptional response to hyperosmotic shock [39]. Approximately 20% of the differentially regulated genes in D. discoideum cells treated with 200 mM sorbitol were dependent on the presence of STATc. The stress response could possibly be the answer to the question of why the simple unicellular amoeba A. castellanii needs STAT signaling.

Bottom Line: A. castellanii is the only, studied to date, Amoebozoan that does not belong to Mycetozoa but possesses STATs.The A. castellanii STAT protein branches next to a group of STATc proteins from Mycetozoa.We also demonstrate that Amoebozoa form a distinct monophyletic lineage within the STAT protein world that is well separated from the other groups.

View Article: PubMed Central - PubMed

Affiliation: Department of Bioenergetics, Adam Mickiewicz University, Poznan, Poland.

ABSTRACT
STAT (signal transducers and activators of transcription) proteins are one of the important mediators of phosphotyrosine-regulated signaling in metazoan cells. We described the presence of STAT protein in a unicellular, free-living amoebae with a simple life cycle, Acanthamoeba castellanii. A. castellanii is the only, studied to date, Amoebozoan that does not belong to Mycetozoa but possesses STATs. A sequence of the A. castellanii STAT protein includes domains similar to those of the Dictyostelium STAT proteins: a coiled coil (characteristic for Dictyostelium STAT coiled coil), a STAT DNA-binding domain and a Src-homology domain. The search for protein sequences homologous to A. castellanii STAT revealed 17 additional sequences from lower eukaryotes. Interestingly, all of these sequences come from Amoebozoa organisms that belong to either Mycetozoa (slime molds) or Centramoebida. We showed that there are four separated clades within the slime mold STAT proteins. The A. castellanii STAT protein branches next to a group of STATc proteins from Mycetozoa. We also demonstrate that Amoebozoa form a distinct monophyletic lineage within the STAT protein world that is well separated from the other groups.

Show MeSH