Effects of chemokine and cytokine treatment on the association of 4E-BP1 with eIF-4E proteins. Factor-starved MO7e cells were treated with control vehicle (lane 1), GM-CSF (lane 2), SLF (lane 3), or GM-CSF + SLF (lane 4) for 1 hour or with MIP-1α (lane 5), IP-10 (lane 6), IL-8 (lane 7), or PF4 (lane 8) for 1 hour before 1 hour of treatment with GM-CSF + SLF. (A) eIF-4E proteins were immunoprecipitated from cell lysates and separated by 15% SDS-PAGE, as described in the Materials and Methods. 4E-BP1 protein content associated with eIF-4E in each treatment group was determined by immunoblotting PVDF membranes with anti–4E-BP1 antibodies and visualized upon exposing ECL-treated membranes to film. The position of the molecular weight marker is indicated to the left. The position of 4E-BP1 is indicated to the right of (B). Scanning analysis of autoradiograms was performed to determine relative 4E-BP1 protein content, as described in the Materials and Methods. (*) 4E-BP1 protein content was significantly higher than control levels for the MIP-1α and IP-10 pretreatment groups (P < .05). (**) Protein content for 4E-BP1 corresponding to the GM-CSF + SLF, IL-8 + GM-CSF + SLF, and PF4 + GM-CSF + SLF treatment groups was significantly less than control levels (P < .05). Each bar represents the mean ± the standard deviation for three determinations obtained in separate experiments. Treatment groups are the same as those for (A).