Role of neuronal Ca²⁺-sensor proteins in Golgi–cell-surface membrane traffic

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.