Vav proteins are involved in the engagement and signaling efficiency of keratinocyte autocrine/paracrine loops.

<p>(A) Quantification by flow cytometry of the apoptosis induced in pure (No) and genotypically mixed (Yes) cultures of wild-type and <i>Vav2</i>^−/−;<i>Vav3</i>^−/− keratinocytes upon 12 h in complete media with DMBA or under serum-free media conditions. (B) Quantification by flow cytometry of the apoptosis observed in wild-type and <i>Vav2</i>^−/−;<i>Vav3</i>^−/− keratinocytes kept for 12 h with serum, without serum, or without serum plus the indicated extracellular factors (<i>n</i> = 3). (C) Determination by flow cytometry of the percentage of wild-type and <i>Vav2</i>^−/−;<i>Vav3</i>^−/− keratinocytes that have entered S phase after 4.5 h under the indicated culture conditions (<i>n</i> = 3). (D–F) Phosphorylation and expression status of Erk and Stat3 in serum-starved wild-type and <i>Vav2</i>^−/−;<i>Vav3</i>^−/− keratinocytes stimulated with either EGF (D) or IL6 (E–G) for the indicated periods of time. In panels (F) and (G), keratinocytes were transduced with empty and Vav-encoding lentiviruses prior to the starvation and stimulation steps as indicated in the respective panel (<i>n</i> = 3). (H) Tyrosine phosphorylation levels of endogenous Vav2 (top panel) in wild-type keratinocytes treated with the indicated agents for 5 min (<i>n</i> = 2). Due to problems with the detection of the endogenous proteins after blot stripping, the loading control shown in the second panel from top was made using a parallel immunoprecipitation with the same anti-Vav2 antibody.