Removal of apoptotic cells by macrophages is required in order to prevent autoimmune responses. Previous studies have reported that group IIA secretory phospholipase A2 (sPLA2) preferentially binds to apoptotic cells and induces a chemotactic factor which promotes the migration of macrophages to apoptotic cells. Based on these observations, we hypothesized that the pool of sPLA2 trapped on apoptotic cells produces chemoattractant lipids that recruit macrophages to phagocytose the apoptotic cells. To test this hypothesis, Jurkat cells were cultured under normal conditions and induced to undergo early apoptosis through treatment with D,L-threo-dihydrosphingosine. Live and early apoptotic cells were incubated with catalytically active sPLA2 and then cell-associated catalytic activity was assessed. In contrast to previous reports, we observed no difference in the ability of live or early apoptotic cells to trap group IIA sPLA2 on their surfaces. However, transmigration assays involving THP-1 monocytes confirmed that the cell-bound pool of sPLA2 generates chemoattractants when bound to the surfaces of live cells. Surprisingly, sPLA2 does not have to be catalytically active to attract THP-1 monocytes. The treatment of live Jurkat cells with heparinase showed a marked reduction in the ability of sPLA2 to bind to live cells and exert catalytic activity, suggesting heparan sulfate proteoglycans are possibly receptors for sPLA2. Future experiments are being planned to identify sPLA2 receptor(s) on THP-1 monocytes.
| Identifer | oai:union.ndltd.org:vcu.edu/oai:scholarscompass.vcu.edu:etd-2756 |
| Date | 20 April 2009 |
| Creators | Chambers, Andria |
| Publisher | VCU Scholars Compass |
| Source Sets | Virginia Commonwealth University |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Theses and Dissertations |
| Rights | © The Author |
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