Phosphatidylglycerol Participates in Syncytium Formation Induced by HTLV Type 1-Bearing Cells

We previously reported that 71-kDa heat shock cognate protein (HSC70) was expressed on the cell surface of human T cell lymphotropic virus type 1 (HTLV-1)-susceptible cells and that HSC70, β-actin, and a lipid-like component on the target cell membrane participated in syncytium formation by HTLV-1. We have now identified this lipid-like component to be palmitoyl (16:0)-oleoyl (18:1)-phosphatidylglycerol (POPG), using preparative thin-layer chromatographic fractionation and tandem mass spectrometric analysis. In the syncytium formation assay, exogenously added PG inhibited cell-to-cell transmission of HTLV-1 in a dose-dependent manner. Other phospholipids showed less (PE) or no effect (PC, PS, PI, PA, lysoPC, lysoPE, and CL). Binding experiments showed that PG interacted with three synthetic peptides, gp46-111, gp46-197, and gp21-400, which correspond to regions Lys111-Asp138 and Asp197-Leu216 on the gp46 surface glycoprotein, and to region Cys400-Leu429 on the gp21 transmembrane glycoprotein, respectively...