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Figure 4 | Retrovirology

Figure 4

From: Pinpointing retrovirus entry sites in cells expressing alternatively spliced receptor isoforms by single virus imaging

Figure 4

Single ASLV-A entry into acidic endosomes and virus-endosome fusion. (A) A diagram illustrating the visualization of the endosomal pH drop and subsequent ASLV-A fusion. (B-E) ASLV-A (yellow) fusion with TVA950 (B, C) and TVA800 (D, E) cells transiently expressing mKO-Rab5 (blue). Pseudoviruses were labeled with EcpH-ICAM (green) and Gag-mKate2 (red). Virus internalization and fusion were initiated by shifting to 37°C at t = 0. (B, D) The right top image panels show consecutive snapshots of the enlarged boxed areas showing the virus prior to internalization (left), immediately after entry into acidic Rab5-positive endosomes (middle) and after fusion with early endosomes (right). The graphs in panel C and E show the fluorescence intensities of mKO-Rab5 and the viral EcpH-ICAM (green) and Gag-mKate2 (red) signals as a function of time. The disappearance of the EcpH signal tended to occur concomitantly with ASLV-A/Rab5 colocalization (raise in the mKO signal). Single particle tracking was performed using the mKate2 channel before colocalization with mKO-Rab5, and using the mKO channel afterward. The colored horizontal bars above the graphs in C and E reflect the pseudocolor changes associated with entry of double-labeled particle into Rab5+ endosomes, lumen acidification and fusion.

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