Absence of p14–MP1 or blockage of Arl8b-dependent late endosomal transport causes IQGAP1 accumulation in FAs. (A) IF: anti-Paxillin and anti-IQGAP1 antibodies. IQGAP1 localizes to the leading edge in p14^f/− (white arrows) and colocalizes with Paxillin in FAs in p14^−/− MEFs (red arrows). (B) IF: anti-Paxillin and anti-IQGAP1 antibodies. Shown are different time points during spreading of p14^f/− and p14^−/− MEFs. White arrows indicate accumulation of IQGAP1 at the leading edge in control MEFs. Red arrows point at IQGAP1 localization at Paxillin-positive FAs in control and p14^−/− MEFs. (C) IF: anti-LAMP1 (green), anti-IQGAP1 (red) antibodies, and Hoechst (blue). IQGAP1 localizes to the leading edge in p14^f/− MEFs treated with control RNAi (white arrows) and localizes to FAs upon Arl8b depletion (red arrows). (D) p14^f/− MEFs treated as in C. IF: anti-Paxillin and anti-IQGAP1 antibodies. Note IQGAP1 localization to the leading edge in p14^f/− MEFs treated with control RNAi (white arrows) versus colocalization of IQGAP1 and Paxillin in FAs upon ARl8b depletion (red arrows).