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

REST is a repressor of a large cluster of neural genes that homeostatically regulates neural activity. However, whether REST can be regulated by Ca ²⁺ and Ca ²⁺ -activated kinases is unknown. We investigated Ca ²⁺ /calmodulin-dependent protein kinases (CaMKs) as upstream regulators of REST fate and activity. We show that REST is phosphorylated by CaMKIV at Ser-322 site located within the linker between the 5 ^th -6 ^th 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 Nterminal 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 CaMKIV phosphorylation has a crucial role in the homeostatic regulation of REST levels and repressor activity.