Shaggy/GSK-3beta kinase localizes to the centrosome and to specialized cytoskeletal structures in Drosophila

The assembly of a functional bipolar mitotic spindle requires an exquisite regulation of microtubule behavior in time and space. To characterize new elements of this machinery we carried out a GFP based "protein trap" screen and selected fusion proteins which localized to the spindle apparatus. By this method we identified Shaggy, the Drosophila homologue of glycogen synthase kinase-3beta (GSK-3beta), as a component of centrosomes. GSK-3beta acting in the Wingless signaling pathway is involved in a vast range of developmental processes, from pattern formation to cell-fate specification, and is a key factor for cell proliferation in most animals. We exploited our Shaggy::GFP Drosophila line to analyze the subcellular localizations of GSK-3beta/Shaggy and shed light on its multiple roles during embryogenesis. We found that Shaggy becomes enriched transiently in a variety of specialized cytoskeletal structures of the embryo, including centrosomes throughout mitosis, suggesting that this kinase is involved in the regulation of many aspects of the cytoskeleton function.