Kong C et al. (2014) Biol Open "Orthosiphon stamineus protects Caenorhabditis elegans against Staphylococcus aureus infection through immunomodulation."

Kong C, Tan MW, Nathan S

[Biol Open, 2014]

Amidst growing concerns over the spread of antibiotic-resistant Staphylococcus aureus strains, the identification of alternative therapeutic molecules has become paramount. Previously, we utilized a Caenorhabditis elegans-S. aureus screening platform to identify potential anti-infective agents from a collection of natural extracts and synthetic compounds. One of the hits obtained from the screen was the aqueous extract of Orthosiphon stamineus leaves (UE-12) that enhanced the survival of infected nematodes without interfering with bacterial growth. In this study, we used a fluorescent transgenic reporter strain and observed that the repressed expression of the lys-7 defense gene in infected nematodes was restored in the presence of UE-12. Analysis of a selected panel of PMK-1 and DAF-16-regulated transcripts and loss-of-function mutants in these pathways indicates that the protective role of UE-12 is mediated via the p38 MAP kinase and insulin-like signaling pathways. Further analysis of a panel of known bioactive compounds of UE-12 proposed eupatorin (C18H16O7) as the possible candidate active molecule contributing to the anti-infective property of UE-12. Taken together, these findings strongly suggest that the O. stamineus leaf extract is a promising anti-infective agent that confers an advantage in survival against S. aureus infection by modulating the immune response of the infected host.

James H Mapes et al. (2005) International Worm Meeting "Characterization of C. elegans annexins, a family of calcium dependent phospholipid binding proteins."

James H Mapes, Ian Arnold, Ding Xue

[International Worm Meeting, 2005]

Alteration of phospholipid asymmetry plays an important role in regulating several important biological processes such as blood coagulation and recognition of apoptotic cells during phagocytosis. Phosphatidylserine (PS) is normally restricted to the inner leaflet of plasma membrane but is externalized during apoptosis. Externalized PS has been suggested to be an eat-me signal for phagocytosis of apoptotic cells. We are interested in understanding how phospholipid asymmetry is generated, recognized, and interpreted during various biological processes. Annexins are a family of calcium-dependent phospholipid binding proteins that may be involved in interpreting phospholipid asymmetry. There are four annexin genes in C. elegans, nex-1, nex-2, nex-3 and nex-4. RNAi treatment of nex-1 causes defects in the clearance of apoptotic cells (1). Interestingly, human Annexin I serves as an adaptor between externalized PS on apoptotic cells and engulfment receptors on macrophages (1). In order to understand the potential functions of the four C. elegans nex genes, we characterized their expression and subcellular localization patterns using GFP fusion proteins and the phenotypes of RNAi-treated animals or deletion mutants. We found that NEX-1, NEX-2, and NEX-3 were broadly expressed in C. elegans and had significant overlaps in their expression patterns. The expression of NEX-4 was restricted to several neurons in the head and tail. The expression of all four NEX genes was not readily apparent until the 4-fold embryonic stage, after most cell deaths and clearance of corpses have occurred. Examination of RNAi-treated animals or two nex gene deletion mutants, nex-1(gk148) and nex-4(gk102), did not reveal any defect in apoptosis, cell corpse engulfment, or other detectable phenotypes. Construction and characterization of double, triple, or quadruple mutants that are defective in multiple nex genes may be important to reveal if nex genes play a role in cell corpse removal or other biological processes. (1) Arur S, Uche UE, Rezaul K, Fong M, Scranton V, Cowan AE, Mohler W, and Han DK (2003). Annexin I is an endogenous ligand that mediates apoptotic cell engulfment. Dev. Cell 4:587-598.

Arur S et al. (2003) Dev Cell "Annexin I is an endogenous ligand that mediates apoptotic cell engulfment."

Rezaul K, Scranton V, Mohler W, Cowan AE, Uche UE, Arur S, Fong M, Han DK

[Dev Cell, 2003]

Engulfment of apoptotic cells requires presentation of new cell surface ligands by the dying cells. Using a differential proteomics technology, we identify that annexin I is a caspase-dependent engulfment ligand; it is recruited from the cytosol and exported to the outer plasma membrane leaflet, colocalizes with phosphatidylserine, and is required for efficient clearance of apoptotic cells. Furthermore, phosphatidylserine receptor (PSR) clustering around apoptotic cells indicates a requirement for annexin I. In the nematode Caenorhabditis elegans, downregulation of the annexin homolog prevents efficient engulfment of pharyngeal cell corpses. These results provide novel mechanistic insights into how apoptotic cells are removed and may explain a pathogenic mechanism of chronic inflammatory diseases where annexin I autoantibodies have been described.