Nucleocytoplasmic Shuttling of the Golgi Phosphatidylinositol 4-Kinase Pik1 Is Regulated by 14-3-3 Proteins and Coordinates Golgi Function with Cell Growth
2008
The yeast phosphatidylinositol 4-kinase Pik1p is essential for
proliferation, and it controls Golgi homeostasis and transport
of newly synthesized proteins from this compartment. At the
Golgi, phosphatidylinositol 4-phosphate recruits multiple
cytosolic effectors involved in formation of post-Golgi
transport vesicles. A second pool of catalytically active Pik1p
localizes to the nucleus. The physiological significance and
regulation of this dual localization of the lipid kinase
remains unknown. Here, we show that Pik1p binds to the
redundant 14-3-3 proteins Bmh1p and Bmh2p. We provide evidence
that nucleocytoplasmic shuttling of Pik1p involves
phosphorylation and that 14-3-3 proteins bind Pik1p in the
cytoplasm. Nutrient deprivation results in relocation of Pik1p
from the Golgi to the nucleus and increases the amount of
Pik1p-14-3-3 complex, a process reversed upon restored nutrient
supply. These data suggest a role of Pik1p nucleocytoplasmic
shuttling in coordination of biosynthetic transport from the
Golgi with nutrient signaling.
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