Src kinases mediate the interaction of the apical determinant bazooka/PAR3 with STAT92E and increase signalling efficiency in Drosophila ectodermal cells

Trabajo presentado a las 1as Jornadas de Señalización Celular y Nuevas Quinasas celebradas en Málaga del 19 al 20 de abril de 2012.Intercellular communication depends on the correct organization of the signal transduction complexes. In many signaling pathways, the mechanisms controlling the overall cell polarity also localize components of these pathways to different domains of the plasma membrane. In the Drosophila ectoderm, the JAK/STAT pathway components are highly polarized with apical localization of the receptor, the associated kinase and the STAT92E protein itself. The apical localization of STAT92E is independent of the receptor complex and is due to its direct association with the apical determining protein Bazooka (Baz). Here, we find that Baz-STAT92E interaction depends on the presence of the Drosophila Src kinases. In the absence of Src, STAT92E cannot bind to Baz in cells or in whole embryos, and this correlates with an impairment of JAK/STAT signalling function. We believe that the requirement of Src proteins for STAT92E apical localization is mediated through Baz, as we can co-precipitate Src with Baz but not with STAT92E. This is the first time that a functional link between cell polarity, the JAK/STAT signalling pathway and the Src kinases has been established in a whole organism.S.S. is a Ramón y Cajal Fellow. J.M.E.-V. is supported through grants from the Ministerio de Educación y Ciencia to J.C.-G.H. This work was supported by grants from the Programa Consolider and the Junta de Andalucía; by Ministerio de Ciencia e Innovación/Fonds Européen de Développement Régional grants to J.C.-G.H. and S.S. [BFU2010-15020 and BFU2010-15851]; and by grants from the Deutsche Forschungsgemeinschaft to M.K. [KR3901/1-1].Peer Reviewe