Plasma Membrane PI4P Regulates Vesicle Docking in Neuronal Exocytosis

Plasma membrane (PM) phosphatidylinositol 4-phosphate (PI4P) plays a crucial role in diverse cellular functions, but its role beyond being a precursor of phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) in secretory pathways including neurotransmitter release and hormone secretion remains unclear. Here, using structured illumination microscopy on the PM of PC12 cells, we show that PI4P is an inner-leaflet lipid that is clustered in microdomain and involved in clustering of t-SNARE protein syntaxin 1 essential for vesicle docking. We found that PI4P interacted with the C2 domain of synaptotagmin 1 and synaptotagmin-like protein 4 in a Ca2+-independent manner, resulting in recruiting SNARE proteins to the target membrane. Interestingly, the frequency of spontaneous excitatory postsynaptic currents (sEPSCs) was decreased by PI4P depletion in cultured hippocampal neurons, particularly it was most significantly decreased when PI(4,5)P2 depleted together. Thus, PI4P contributes to anionic PM lipid pool for SNARE-lipid interaction at vesicle docking stage of neuronal exocytosis.