K-Ras activation of Rac <i>in vivo</i>.

<p>(<b>A</b>) Active Rac1 was immunoprecipitated from lysates derived from NIH 3T3 cells that had been treated for the indicated time periods with PDGF (10 ng/ml). Western analysis for Rac1 was carried out on immunoprecipitated protein as well as the original lysate as indicated. (<b>B</b>) Histogram showing active Rac1 immunofluorescence intensity averaged over 5 fields of NIH 3T3 cells increasing over the indicated time periods of PDGF treatment. (<b>C</b>) Staining for actin with Texas-red conjugated phalloidin (red) and co-immunofluorescence for active Rac1 (green) in representative fields of NIH 3T3 cells used in the quantification shown in panel B, demonstrating increased active Rac1 and changes to the actin cytoskeleton over the indicated time periods of PDGF treatment. Boxed areas indicated by numbers 1-3 are shown enlarged. (<b>D</b>) Immunohistochemical analysis for Rac1 and active Rac1 of oral mucosa from LSL-K-Ras^G12D, LSL-K-Ras^G12D; K14-Cre:ER and Rac1^Wt/-; LSL-K-Ras^G12D; K14-Cre:ER showing dramatic increase in active Rac1 in LSL-K-Ras^G12D; K14-Cre:ER tissue, which is reduced when one Rac1 allele is lacking. Histogram shows results of positive pixel analysis for active Rac1staining.