A, pak1 was immunoprecipitated from extracts of tracheal smooth muscle tissues stimulated for 5 min with ACh or unstimulated (US) and treated with Pak K299R to inhibit Pak activation or not treated (Sham) (n = 4). B, Pak1 was immunoprecipitated from extracts of canine tracheal smooth muscle tissues stimulated for 5 min with ACh or unstimulated (US) and treated with IPA3 to inhibit Pak activation or not treated (n = 7). C, Pak1 or Pak2 was immunoprecipitated from extracts of canine tracheal smooth muscle tissues stimulated for 5 min with ACh or unstimulated (US). ACh induced an increase in GIT1, βPIX and paxillin co‐immunoprecipitation with either Pak1 or Pak2. Pak1 and Pak2 were immunoblotted using a pan‐Pak antibody. D, in situ PLA shows the interaction of paxillin and GIT1 in freshly dissociated differentiated canine tracheal smooth muscle cells. PLA fluorescence and phase contrast images are shown for each cell. In cells from sham‐treated tissues, the mean number of PLA spots was significantly higher in ACh‐stimulated cells than in unstimulated cells (n = 30 for US; n = 34 for ACh). In cells from Pak K299R‐treated tissues, the mean number of PLA spots was very small and did not change significantly with ACh stimulation (n = 33 for US; n = 34 for ACh). Cells dissociated from tissues obtained from four separate experiments. *Significant difference between effects of treatments on ACh‐stimulated cells, P < 0.05. Values are means ± SEM. IP, immunoprecipitate; IB, immunoblot.