The intracellular localisation and mobility of Type Iγ phosphatidylinositol 4P 5-kinase splice variants

There are three known splice variants of Type Iγ phosphatidylinositol 4-phosphate 5-kinase (PIPkin Iγ): PIPkins Iγ87, Iγ90, and the most recently cloned (Giudici, M.L., Emson, P.C. and Irvine, R.F. (2004) A novel neuronal-specific splice variant of Type I phosphatidylinositol 4-phosphate 5-kinase isoform gamma. Biochem. J. 379, 489–496) PIPkin IγC (here called PIPkin Iγ93). Here, we have explored the subcellular localisation and mobility of Type I PIPkins in transfected cells by confocal microscopy and flourescence recovery after photobleaching. The unique behaviour shown by PIPkin Iγ93 is consistent with its suggested distinct function. Moreover, the markedly different localisation and mobility of active versus inactive PIPkin Iγ93 provide insights into the factors that dictate cellular targeting of Type Iγ PIPkins.