Coexpression of c-myc–epitope–tagged 4.1R⁸⁰and HA-epitope–tagged 4.1R⁸⁰▵E16 isoforms in transfected COS-7 cells. COS-7 cells were cotransfected with c-myc–epitope–tagged 4.1R⁸⁰ and HA-epitope–tagged 4.1R⁸⁰▵E16 isoforms, fixed with 3% paraformaldehyde, permeabilized with 0.5% Triton X-100, and processed for immunofluorescence using a monoclonal anti-c-myc–epitope tag antibody and a polyclonal anti–HA-epitope tag antibody as primary antibodies and anti-mouse IgG coupled to Texas red and rabbit IgG coupled to FITC as secondary antibodies. A cell probed with antibody to the c-myc–epitope tag showed that 4.1R⁸⁰was strongly expressed in the nucleus as well as in the cytoplasm and membrane ruffles (a). In marked contrast, the same cell probed with antibody to the HA-epitope tag (b) showed that 4.1R⁸⁰▵E16 localized poorly to the nucleus but was strongly expressed in the cytoplasm as well as in membrane ruffles. Superimposed images of (a) and (b) are shown in (c). Scale bar: 10 μm.