Schematic representation of STIM1 functions in the soma and dendrites of PNs. Left, A previous study (Hartmann et al., 2014) suggested that STIM1 is important for maintaining dendritic ER Ca2+ stores at rest. Schematic representation of STIM1 functions in the soma and dendrites of PNs. Left, A previous study (Hartmann et al., 2014) suggested that STIM1 is important for maintaining dendritic ER Ca2+ stores at rest. The regulation of dendritic Ca2+ homeostasis by STIM1 is essential for mGluR1-dependent synaptic transmission. Right, Our study described a novel, additional STIM1 function: the regulation of the somatic Ca2+ dynamics of firing neurons. The regulation of somatic Ca2+ dynamics, and thereby Ca2+-sensitive ion channels, by STIM1 contributes to normal neuronal firing. Solid lines indicate well established interactions, and dashed lines indicate interactions not fully described in detail. Arrows indicate activation pathways, and a blunt end indicates the inhibition pathway. Changhyeon Ryu et al. J. Neurosci. 2017;37:8876-8894 ©2017 by Society for Neuroscience