Abstract
CaMKII is an important mediator of forms of synaptic plasticity that are thought to underly learning and memory. The CaMKII mutants K42M and K42R have been used interchangeably as research tools, although some reported phenotypic differences suggest that they may differ in the extent to which they impair ATP binding. Here, we directly compared the two mutations at the high ATP concentrations that exist within cells (~4 mM). We found that both mutations equally blocked GluA1 phosphorylation in vitro and GluN2B binding within cells. Both mutations also reduced but did not completely abolish CaMKII T286 autophosphorylation in vitro or CaMKII movement to excitatory synapses in neurons. Thus, despite previously suggested differences, both mutations appear to interfere with ATP binding to the same extent.
Highlights
The Ca2+/calmodulin(CaM)-dependent protein kinase II (CaMKII; Fig 1) is a major mediator of higher brain functions such as learning and memory, as well as of the underlying forms of synaptic plasticity, including long-term potentiation (LTP) of excitatory glutamatergic synapses [1,2,3,4]
Normal LTP is expressed largely by potentiation of synaptic AMPA-type glutamate receptors (AMPARs) [5,6,7] and is thought to require (i) Ca2+-stimulated CaMKII activity [8,9,10], (ii) the CaMKII T286 autophosphorylation that generates Ca2+-independent “autonomous” activity [11, 12], and (iii) the CaMKII binding to the NMDA-type glutamate receptor (NMDAR) subunit GluN2B that underlies much of the CaMKII targeting to excitatory synapses [13,14,15,16]
We decided to determine if reduction in ATP binding is sufficient to block kinase activity for both mutants at high ATP concentrations (4 mM, i.e. the approximate typical concentration found within cells)
Summary
The Ca2+/calmodulin(CaM)-dependent protein kinase II (CaMKII; Fig 1) is a major mediator of higher brain functions such as learning and memory, as well as of the underlying forms of synaptic plasticity, including long-term potentiation (LTP) of excitatory glutamatergic synapses [1,2,3,4]. Normal LTP is expressed largely by potentiation of synaptic AMPA-type glutamate receptors (AMPARs) [5,6,7] and is thought to require (i) Ca2+-stimulated CaMKII activity [8,9,10], (ii) the CaMKII T286 autophosphorylation that generates Ca2+-independent “autonomous” activity [11, 12], and (iii) the CaMKII binding to the NMDA-type glutamate receptor (NMDAR) subunit GluN2B that underlies much of the CaMKII targeting to excitatory synapses [13,14,15,16] All three of these functions require nucleotide binding to CaMKII: Whereas ATP binding is an obvious requirement for kinase activity (including autophosphorylation), nucleotide binding is required for efficient binding to GluN2B [17,18,19].
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