Regulation of Lipid Composition of the Golgi during Tissue Formation: Where Does PI 4-Kinase Stand?

Four Wheel Drive (Fwd), the Drosophila homologue of PI 4-kinase IIIβ, is a conserved phosphatidylinositol 4-kinase (PI4K) that localizes to the Golgi apparatus and functions in protein trafficking from the Golgi to the plasma membrane. The goal of this project was to determine how the localization of Fwd to the Golgi is regulated during early embryogenesis in Drosophila. Our initial observations suggested that Fwd was only localized to a subset of Golgi apparatus, raising the question of whether distinct types of Golgi apparatus exist in early Drosophila embryos. By optimizing imaging conditions, we found that many Golgi compartments initially identified as Fwd-negative showed weak Fwd-GFP signals, arguing against the existence of a sub-population of Golgi that completely lack Fwd. In addition, we found that phosphatidylinositol 4-phosphate (PI4P), the lipid product of PI4Ks, were both strongly enriched on the plasma membrane and weakly associated with intracellular puncta-like structures. These intracellular signals appear to overlap with Fwd-GFP, suggesting that Fwd colocalizes with its lipid product on the Golgi apparatuses. Together, our findings demonstrate that Golgi apparatuses differ in their capacity to recruit Fwd, which may impact their rate of PI4P production. These observations raise the question of how the activity of individual Golgi apparatuses are regulated in developing tissues. ; https://digitalcommons.dartmouth.edu/wetterhahn_2024/1003/thumbnail.jpg