REST/NRSF phosphorylation by CaMKIV regulates its transcriptional repressor activity and half-life

REST is a repressor of a large cluster of neural genes containing RE1 motifs. In neurons, REST homeostatically regulates intrinsic excitability and synaptic transmission, However, whether REST can be regulated by Ca2+ and Ca2+-activated kinases is unknown. Here, we investigated Ca2+/calmodulin-dependent protein kinases (CaMKs) as upstream regulators of REST fate and activity. We show that REST is phosphorylated by CaMKIV at a main Ser-322 site located within the linker between the 5th and the 6th N-terminal Zn-finger domains. Phosphomimic REST mutant in Serine-322 decreased REST repressor activity and caused its transition from nucleus to cytosol, followed by degradation. Molecular dynamics simulations of the phosphomimic N-terminal REST and the DNA RE1 sequence revealed a sharp decrease in the stability of the REST-RE1 binding interface. Moreover, the homeostatic effects of CaMKIV on the amplitude of excitatory synaptic currents were inhibited by the genetic deletion of REST. The results demonstrate that REST phosphorylation by CaMKIV regulates the repressor activity of REST on neural genes and has a crucial role in the homeostatic regulation of REST levels.