Investigation of CaMKII activation: a model of self-regulation

Abstract

Presently we do not completely understand how memories are able to store, retain, and recall information and experiences. The investigation is just beginning and proteins key for the biochemical processes associated with memory are currently being identified and characterized. Calcium-calmodulin dependent protein kinase II (CaMKII) has been deemed one of these “memory molecules” because of the critical role it plays in memory and learning. Memories are thought to be encoded by synaptic strength modification and CaMKII has been shown to be critical for the normal regulation of synaptic transmission. CaMKII functions as a transducer of calcium (Ca2+) signaling by responding to the amplitude, duration, and frequency of Ca2+ transients. Autophosphorylation at Thr286 following binding of calcium-calmodulin (Ca2+/CaM) leads to a Ca2+-independent activity referred to as a conformational memory of prior activation. While CaM binding, autophosphorylation, and catalytic-regulatory domain autoinhibition have been linked to CaMKII function, the underlying structural and dynamic framework of activation and conformational memory is poorly understood. We utilized site-directed spin labeling and electron paramagnetic resonance (SDSL-EPR) to explore the conformational changes associated with CaMKII activation and conformational memory. The structure of the regulatory domain was investigated via spin label mobility under several conditions representing various intermediates of activation. Inter-domain movements were also examined through distance measurements between regulatory and catalytic domains. We found that CaMKII activation is associated with regulatory-catalytic domain disengagement, causing a disruption of autoinhibition and producing significant conformational changes which are propagated throughout the regulatory domain. Here we detail a mechanistic description of activation and are currently using EPR data to computationally model conformational changes associated with CaMKII activation.