Long-term depression in neurons involves temporal and ultra-structural dynamics of phosphatidylinositol-4,5-bisphosphate relying on PIP5K, PTEN and PLC.

Synaptic plasticity involves proper establishment and rearrangement of structural and functional microdomains. Yet, visualization of the underlying lipid cues proved challenging. Applying a combination of rapid cryofixation, membrane freeze-fracturing, immunogold labeling and electron microscopy, we visualize and quantitatively determine the changes and the distribution of phosphatidylinositol-4,5-bisphosphate (PIP 2 ) in the plasma membrane of dendritic spines and subareas thereof at ultra-high resolution. These efforts unravel distinct phases of PIP 2 signals during induction of long-term depression (LTD). During the first minutes PIP 2 rapidly increases in a PIP5K-dependent manner forming nanoclusters. PTEN contributes to a second phase of PIP 2 accumulation. The transiently increased PIP 2 signals are restricted to upper and middle spine heads. Finally, PLC-dependent PIP 2 degradation provides timely termination of PIP 2 cues during LTD induction. Together, this work unravels the spatial and temporal cues set by PIP 2 during different phases after LTD induction and dissects the molecular mechanisms underlying the observed PIP 2 dynamics.