The regulated local synthesis of PtdIns4P and PtdIns(4,5)P2 is crucial for TGN (trans-Golgi network)–plasma membrane trafficking. The activity of PI4Kβ (phosphoinositide 4-kinase IIIβ) at the Golgi membrane is a first mandatory step in this process. In addition to PI4Kβ activity, elevated Ca2+ levels are also needed for the exit of vesicles from the TGN. The reason for this Ca2+ requirement is at present unclear. In the present review, we discuss the role of neuronal Ca2+-sensor proteins in the regulation of PI4Kβ and suggest that this regulation might impose a need for elevated Ca2+ levels for a late step of vesicle assembly.

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