Institute of Biology, Cellular Biophysics, Humboldt Universität zu Berlin, Berlin, Germany; Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Berlin, Germany
Léonie Héluin
Institute of Biology, Cellular Biophysics, Humboldt Universität zu Berlin, Berlin, Germany; Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Berlin, Germany
Pin-Lian Jiang
Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Berlin, Germany
Alejandro G Castro Scalise
Institute of Biology, Cellular Biophysics, Humboldt Universität zu Berlin, Berlin, Germany; Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Berlin, Germany
Cong Wang
Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Berlin, Germany
Andreas Franz
Institute of Chemistry and Biochemistry, Freie Universität Berlin, Berlin, Germany
Institute of Chemistry and Biochemistry, Freie Universität Berlin, Berlin, Germany; Helmholtz-Zentrum Berlin für Materialien und Energie, Macromolecular Crystallography, Berlin, Germany
Fan Liu
Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Berlin, Germany; Charité-Universitätsmedizin Berlin, Berlin, Germany
Institute of Biology, Cellular Biophysics, Humboldt Universität zu Berlin, Berlin, Germany; Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Berlin, Germany; NeuroCure, Charité Universitätsmedizin, Berlin, Germany
The dodecameric protein kinase CaMKII is expressed throughout the body. The alpha isoform is responsible for synaptic plasticity and participates in memory through its phosphorylation of synaptic proteins. Its elaborate subunit organization and propensity for autophosphorylation allow it to preserve neuronal plasticity across space and time. The prevailing hypothesis for the spread of CaMKII activity, involving shuffling of subunits between activated and naive holoenzymes, is broadly termed subunit exchange. In contrast to the expectations of previous work, we found little evidence for subunit exchange upon activation, and no effect of restraining subunits to their parent holoenzymes. Rather, mass photometry, crosslinking mass spectrometry, single molecule TIRF microscopy and biochemical assays identify inter-holoenzyme phosphorylation (IHP) as the mechanism for spreading phosphorylation. The transient, activity-dependent formation of groups of holoenzymes is well suited to the speed of neuronal activity. Our results place fundamental limits on the activation mechanism of this kinase.
