Fig. 2.

Nonraft HA has reduced cell–cell fusion capacity as compared with WT HA at equivalent overall surface density of HA. (A) HA fusion activity of WT and nonraft mutant HA 530–532 was measured by binding RBCs dual-labeled with lipid probe octadecyl rhodamine (R18) and aqueous cytoplasmic probe CF to BHK cells transiently expressing HAs and triggering fusion by low pH treatment (pH 4.8 for 1 min). MFI, mean fluorescent intensity. (B) Quantification of fusion events for BHK cells expressing different cell surface densities of HAs as measured by flow cytometry. Average fusion events and standard deviations are from three to five microscopic fields per experiment. MFI, mean fluorescent intensity.