Spines and neurite branches function as geometric attractors that enhance protein kinase C action

Ca²⁺ and diacylglycerol-regulated protein kinase Cs (PKCs; conventional PKC isoforms, such as PKCγ) are multifunctional signaling molecules that undergo reversible plasma membrane translocation as part of their mechanism of activation. In this article, we investigate PKCγ translocation in hippocampal neurons and show that electrical or glutamate stimulation leads to a striking enrichment of PKCγ in synaptic spines and dendritic branches. Translocation into spines and branches was delayed when compared with the soma plasma membrane, and PKCγ remained in these structures for a prolonged period after the response in the soma ceased. We have developed a quantitative model for the translocation process by measuring the rate at which PKCγ crossed the neck of spines, as well as cytosolic and membrane diffusion coefficients of PKCγ. Our study suggests that neurons make use of a high surface-to-volume ratio of spines and branches to create a geometric attraction process for PKC that imposes a delayed enhancement of PKC action at synapses and in peripheral processes.