Figure 5.

Epithelial rescue by p120 is both expression level and isoform dependent. (A) Isolation by GFP FACS of cell populations expressing low or high levels of p120 isoforms. Cells were infected with viruses containing GFP alone (lanes 1 and 5) or GFP linked by an IRES to p120 isoforms 1A (lanes 2 and 6), 3A (lanes 3 and 7), or 4A (lanes 4 and 8). Cells were sorted by FACS for low (lanes 1–4) and high (lanes 5–8) GFP expression. Protein normalization was confirmed by Western blotting with GM130 antibody. Note the tight correlation between GFP and p120 levels. Each isoform expression level is roughly equivalent within low and high level groups. (B) Quantification of the potency of p120 rescue as a function of expression level and isoform. Cells sorted as described above were plated at low density, grown into clonal colonies, and the colonies scored as compact or loose. The data reflect the ratio of compacted (rescued) colonies divided by the total number of colonies. Compacted colonies occurred more frequently when p120 is expressed at high levels. p120ctn4, which lacks the NH₂-terminal phosphorylation domain, is more efficient at inducing compaction than p120ctn1 and 3, which retain this domain.