Protein kinase C (PKC) is a family of kinases, one of which is the well-studied polarity protein atypical PKC (aPKC). These kinases must be phosphorylated before their catalytic domain is activated. The protein PDK1 serves to phosphorylate and activate newly-made PKC proteins, and a recent paper reveals that it can also phosphorylate older PKC proteins that have been since dephosphorylated, seen as a “rescue” of activity. Mashukova and colleagues also found that PDK1 is localized in membrane compartments on the apical side of some epithelial cells in close proximity to intermediate filaments, suggesting a new signaling function in these membrane compartments (endosomes). In the images above, epithelial cells have PDK1 (red) localized to the apical pole of the cells, where intermediate filaments (green) are found.
Mashukova, A., Forteza, R., Wald, F., & Salas, P. (2012). PDK1 in apical signaling endosomes participates in the rescue of the polarity complex atypical PKC by intermediate filaments in intestinal epithelia Molecular Biology of the Cell, 23 (9), 1664-1674 DOI: 10.1091/mbc.E11-12-0988