Lateral diffusion of inositol 1,4,5-trisphosphate receptor type 1 in Purkinje cells is regulated by calcium and actin filaments

Abstract

Inositol 1,4,5-trisphosphate receptor type 1 (IP3R1) is an intracellular Ca2+ release channel that plays crucial roles in the functions of Purkinje cells. The dynamics of IP3R1 on the endoplasmic reticulum membrane and the distribution of IP3R1 in neurons are thought to be important for the spatial regulation of Ca2+ release. In this study, we analyzed the lateral diffusion of IP3R1 in Purkinje cells in cerebellar slice cultures using fluorescence recovery after photobleaching. In the dendrites of Purkinje cells, IP3R1 showed lateral diffusion with an effective diffusion constant of approximately 0.30 μm2/s, and the diffusion of IP3R1 was negatively regulated by actin filaments. We found that actin filaments were also involved in the regulation of IP3R1 diffusion in the spine of Purkinje cells. Glutamate or quisqualic acid stimulation, which activates glutamate receptors and leads to a Ca2+ transient in Purkinje cells, decreased the diffusion of IP3R1 and increased the density of actin in spines. These findings indicate that the neuronal activity-dependent augmentation of actin contributes to the stabilization of IP3R1 in spines. © 2010 International Society for Neurochemistry.