Gastrodermal lipid bodies (LBs) are organelles involved in the regulation of the mutualistic endosymbiosis between reef-building corals and their dinoflagellate endosymbionts (genus Symbiodinium). As their molecular composition remains poorly defined, we herein describe the first gastrodermal LB proteome and examine in situ morphology of LBs in order to provide insight into their structure and function. After tissue separation of the tentacles of the stony coral Euphyllia glabrescens, buoyant LBs of the gastroderm encompassing a variety of sizes (0.5-4 μm in diameter) were isolated after two cycles of subcellular fractionation via stepwise sucrose gradient ultracentrifugation and detergent washing. The purity of the isolated LBs was demonstrated by their high degree of lipid enrichment and as well as the absence of contaminating proteins of the host cell and Symbiodinium. LB-associated proteins were then purified, subjected to SDS-PAGE, and identified by MS using an LC-nano-ESI-MS/MS. A total of 42 proteins were identified within eight functional groups, including metabolism, intracellular trafficking, the stress response/molecular modification and development. Ultrastructural analyses of LBs in situ showed that they exhibit defined morphological characteristics, including a high-electron density resulting from a distinct lipid composition from that of the lipid droplets of mammalian cells. Coral LBs were also characterized by the presence of numerous electron-transparent inclusions of unknown origin and composition. Both proteomic and ultrastructural observations seem to suggest that both Symbiodinium and host organelles, such as the ER, are involved in LB biogenesis.
Symbiosomes are specific intracellular membrane-bound vacuoles containing microalgae in a mutualistic Cnidaria (host)-dinoflagellate (symbiont) association. The symbiosome membrane is originally derived from host plasma membranes during phagocytosis of the symbiont; however, its molecular components and functions are not clear. In order to investigate the protein components of the symbiosome membranes, homogenous symbiosomes were isolated from the sea anemone Aiptasia pulchella and their purities and membrane intactness examined by Western blot analysis for host contaminants and microscopic analysis using various fluorescent probes, respectively. Pure and intact symbiosomes were then subjected to biotinylation by a cell impermeant agent (Biotin-XX sulfosuccinimidyl ester) to label membrane surface proteins. The biotinylated proteins, both Triton X-100 soluble and insoluble fractions, were subjected to 2-D SDS-PAGE and identified by MS using an LC-nano-ESI-MS/MS. A total of 17 proteins were identified. Based on their different subcellular origins and functional categories, it indicates that symbiosome membranes serve as the interface for interaction between host and symbiont by fulfilling several crucial cellular functions such as those of membrane receptors/cell recognition, cytoskeletal remodeling, ATP synthesis/proton homeostasis, transporters, stress responses/chaperones, and anti-apoptosis. The results of proteomic analysis not only indicate the molecular identity of the symbiosome membrane, but also provide insight into the possible role of symbiosome membranes during the endosymbiotic association.
S100P, a Ca2+ binding protein, has been shown to be overexpressed in various cancers. However, its functional character in lung cancer remains largely unknown. In this study, we show that S100P increases cancer migration, invasion and metastasis in lung cancer cells. Ectopic expression of S100P increases migration, invasion and EMT in less invasive CL1-0 lung cancer cells. Conversely, knockdown of S100P suppressed migration and invasion, and caused a reversion of EMT in highly invasive lung cancer cells. These effects were transduced by increasing the interaction of S100P with integrin α7, which activated focal adhesion kinase (FAK) and AKT. Blocking FAK significantly decreased S100P-induced migration by decreasing Src and AKT activation, whereas inhibiting AKT reduced S100P upregulation on ZEB1 expression. Further study has indicated that S100P knockdown prevents the spread of highly metastatic human lung cancer in animal models. This study therefore suggests that S100P represents a critical activator of lung cancer metastasis. Detection and targeted treatment of S100P-expressing cancer is an attractive therapeutic strategy in treating lung cancer.
Aggregation-induced emission enhancement (AIEE) of thiolated gold nanoclusters (AuNCs) has emerged as an attractive and alternative strategy to improve their brightness. This study demonstrates Ce(iii)-triggered AIEE of glutathione-capped AuNCs (GSH-AuNCs) through the coordination between two carboxylic groups of GSH and Ce(iii). The cluster size and valence state of GSH-AuNCs are almost identical to those of a Ce(iii)-induced assembly of GSH-AuNCs (named Ce(iii)-GSH-AuNCs). More importantly, the as-prepared Ce(iii)-GSH-AuNCs exhibit a higher quantum yield (up to 13%), longer luminescence lifetime, and shorter maximum luminescence peak than GSH-AuNCs. Additionally, Ce(iii)-GSH-AuNCs possess redox-switchable luminescence, high salt stability, and long-term storage stability. These findings provide clear evidence that the Ce(iii)-triggered aggregation of GSH-AuNCs is a crucial factor to improve the luminescence property of GSH-AuNCs. Intriguingly, the presence of adenosine triphosphate (ATP) switches off the luminescence of Ce(iii)-GSH AuNCs through the significant formation of Ce(iii)-ATP complexes. Furthermore, the ATP-induced luminescence quenching of Ce(iii)-GSH-AuNCs can be paired with the alkaline phosphatase (ALP)-ATP system to design a turn-on luminescent probe for ALP; the limit of detection for ALP is estimated to be 0.03 U L-1. Also, the biocompatibility of Ce(iii)-GSH-AuNCs enables the proposed system to detect ALP in human serum and HeLa cells.
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