Lobe-specific Functions of Ca2+·Calmodulin in αCa2+·Calmodulin-dependent Protein Kinase II Activation

Abstract

N-Methyl-d-aspartic acid receptor-dependent long term potentiation (LTP), a model of memory formation, requires Ca2+·calmodulin-dependent protein kinase II (αCaMKII) activity and Thr286 autophosphorylation via both global and local Ca2+ signaling, but the mechanisms of signal transduction are not understood. We tested the hypothesis that the Ca2+-binding activator protein calmodulin (CaM) is the primary decoder of Ca2+ signals, thereby determining the output, e.g. LTP. Thus, we investigated the function of CaM mutants, deficient in Ca2+ binding at sites 1 and 2 of the N-terminal lobe or sites 3 and 4 of the C-terminal CaM lobe, in the activation of αCaMKII. Occupancy of CaM Ca2+ binding sites 1, 3, and 4 is necessary and sufficient for full activation. Moreover, the N- and C-terminal CaM lobes have distinct functions. Ca2+ binding to N lobe Ca2+ binding site 1 increases the turnover rate of the enzyme 5-fold, whereas the C lobe plays a dual role; it is required for full activity, but in addition, via Ca2+ binding site 3, it stabilizes ATP binding to αCaMKII 4-fold. Thr286 autophosphorylation is also dependent on Ca2+ binding sites on both the N and the C lobes of CaM. As the CaM C lobe sites are populated by low amplitude/low frequency (global) Ca2+ signals, but occupancy of N lobe site 1 and thus activation of αCaMKII requires high amplitude/high frequency (local) Ca2+ signals, lobe-specific sensing of Ca2+-signaling patterns by CaM is proposed to explain the requirement for both global and local Ca2+ signaling in the induction of LTP via αCaMKII.

Fast-Response Calmodulin-Based Fluorescent Indicators Reveal Rapid Intracellular Calcium Dynamics

“…We have previously shown that the mutation of the Trp residue to Tyr in a RS20-related peptide increases the K d of the complex for Ca 2+ .CaM 19 20 . Moreover, disabling individual EF-hand Ca 2+ binding sites of CaM by single point mutations (Asp → Ala) in the first loop residue of each EF-hand increased the K d of CaM for Ca 2+ 21 22 . As a consequence, Ca 2+ dissociation from complexes of Ca 2+ -bound EF-hand mutated CaM with a peptide derived from αCaMKII (CaMKIIP) was significantly accelerated.…”

Second Messengers Mediating the Expression of Neuroplasticity in a Model of Chronic Pain in the Rat

“…Furthermore, this protein translation depends on activation of 3 molecules previously shown to be involved in learning and memory (another form of long-lasting neuroplasticity 20 ): the cytoplasmic polyadenylation element binding protein (CPEB; a molecule that regulates translation of dormant mRNAs) 42,51 , αCaMKII 8,10,12,25,26,54 , and ryanodine receptors (which can activate αCaMKII, 43,44,53 ). In this study, we tested if 3 molecules that participate in the induction of the primed state, PKCε, αCaMKII and the ryanodine receptor 20 , also play a role in the prolonged phase of hyperalgesia that is induced by a PGE 2 challenge in the primed state.…”

Peripheral Administration of Translation Inhibitors Reverses Increased Hyperalgesia in a Model of Chronic Pain in the Rat

“…Richter and colleagues have enumerated mRNA species in axonal processes/neural tissue that have polyadenylation tails and are thus downstream targets of CPEB 26,27,41,44 . Amongst these, one, calcium/calmodulin-dependent protein kinase II (CaMKII), has also been implicated in neuroplasticity 6,7,8,14,19,58 . Of note, CaMKII can be both upstream, regulating the activation of CPEB 3 as well as downstream of CPEB 18,56 .…”