RESUMEN
Charting the emergence of eukaryotic traits is important for understanding the characteristics of organisms that contributed to eukaryogenesis. Asgard archaea and eukaryotes are the only organisms known to possess regulated actin cytoskeletons. Here, we determined that gelsolins (2DGels) from Lokiarchaeota (Loki) and Heimdallarchaeota (Heim) are capable of regulating eukaryotic actin dynamics in vitro and when expressed in eukaryotic cells. The actin filament severing and capping, and actin monomer sequestering, functionalities of 2DGels are strictly calcium controlled. We determined the X-ray structures of Heim and Loki 2DGels bound actin monomers. Each structure possesses common and distinct calcium-binding sites. Loki2DGel has an unusual WH2-like motif (LVDV) between its two gelsolin domains, in which the aspartic acid coordinates a calcium ion at the interface with actin. We conclude that the calcium-regulated actin cytoskeleton predates eukaryogenesis and emerged in the predecessors of the last common ancestor of Loki, Heim and Thorarchaeota.
Asunto(s)
Actinas , Calcio , Citoesqueleto de Actina/metabolismo , Actinas/metabolismo , Archaea/metabolismo , Calcio/metabolismo , Gelsolina/química , Gelsolina/metabolismoRESUMEN
The origin of the eukaryotic cell is one of the greatest mysteries in modern biology. Eukaryotic-wide specific biological processes arose in the lost ancestors of eukaryotes. These distinctive features, such as the actin cytoskeleton, define what it is to be a eukaryote. Recent sequencing, characterization, and isolation of Asgard archaea have opened an intriguing window into the pre-eukaryotic cell. Firstly, sequencing of anaerobic sediments identified a group of uncultured organisms, Asgard archaea, which contain genes with homology to eukaryotic signature genes. Secondly, characterization of the products of these genes at the protein level demonstrated that Asgard archaea have related biological processes to eukaryotes. Finally, the isolation of an Asgard archaeon has produced a model organism in which the morphological consequences of the eukaryotic-like processes can be studied. Here, we consider the consequences for the Asgard actin cytoskeleton and for the evolution of a regulated actin system in the archaea-to-eukaryotic transition.
Asunto(s)
Citoesqueleto de Actina/genética , Archaea/citología , Proteínas Arqueales/genética , Evolución Biológica , Células Eucariotas/citología , Citoesqueleto de Actina/química , Citoesqueleto de Actina/fisiología , Actinas/química , Actinas/genética , Animales , Archaea/química , Archaea/genética , Archaea/aislamiento & purificación , Proteínas Arqueales/química , Proteínas Arqueales/fisiología , Eucariontes/citología , Eucariontes/genética , Eucariontes/metabolismo , Células Eucariotas/química , Células Eucariotas/fisiología , Humanos , Metagenómica , Filogenia , Análisis de Secuencia de ProteínaRESUMEN
Cholangiocarcinoma (CCA), a malignancy of biliary epithelium, is related to liver stem cell deregulation. FoxAs are a group of transcription factors that play critical roles in liver stem cell differentiation. In this study, the expression levels of FoxAs (i.e., FoxA1, FoxA2 and FoxA3) were detected in intrahepatic CCA tissues and the functions of FoxAs were studied in CCA cell lines. FoxA1 and FoxA2 were mainly localized in the nuclei of normal bile duct (NBD) cells and some of the cancer cells. Low expression of FoxA1 in CCA tissues (72%) was significantly correlated with poor prognosis. FoxA3 expression of CCA cells was localized in the nucleus and cytoplasm, whereas it was slightly detected in NBDs. High expression of FoxA3 in cancer tissues (61%) was significantly related to high metastasis status. These findings suggest the opposing roles of FoxA1 and FoxA3 in CCA. Moreover, the FoxA1-over-expressing CCA cell line exhibited a significant reduction in proliferative and invasive activities compared to control cells. Knockdown of FoxA3 in CCA cells resulted in a significant decrease in proliferative and invasive activities compared with control cells. Taken together, in CCA, FoxA1 is down-regulated and has tumor suppressive roles, whereas FoxA3 is up-regulated and has oncogenic roles.
