A mechanism for Ca2+/calmodulin-dependent protein kinase II clustering at synaptic and nonsynaptic sites based on self-association.

Publication Type:

Journal Article

Authors:

Hudmon, Andy; Lebel, Eric; Roy, Hugo; Sík, Attila; Schulman, Howard; Waxham, M Neal; Paul De Koninck

Source:

J Neurosci, Volume 25, Issue 30, p.6971-83 (2005)

Keywords:

Animals, Calcium, Calcium-Calmodulin-Dependent Protein Kinase Type 2, Calcium-Calmodulin-Dependent Protein Kinases, Cell Membrane, Cells, Cultured, Green Fluorescent Proteins, Hippocampus, Humans, Hydrogen-Ion Concentration, Kidney, Neurons, Phosphorylation, Protein Structure, Tertiary, Rats, Receptors, Glutamate, Synapses, Threonine, Transfection

Abstract:

<p>The activity of Ca2+/calmodulin-dependent protein kinase II (CaMKII) plays an integral role in regulating synaptic development and plasticity. We designed a live-cell-imaging approach to monitor an activity-dependent clustering of green fluorescent protein (GFP)-CaMKII holoenzymes, termed self-association, a process that we hypothesize contributes to the translocation of CaMKII to synaptic and nonsynaptic sites in activated neurons. We show that GFP-CaMKII self-association in human embryonic kidney 293 (HEK293) cells requires a catalytic domain and multimeric structure, requires Ca2+ stimulation and a functional Ca2+/CaM-binding domain, is regulated by cellular pH and Thr286 autophosphorylation, and has variable rates of dissociation depending on Ca2+ levels. Furthermore, we show that the same rules that govern CaMKII self-association in HEK293 cells apply for extrasynaptic and postsynaptic translocation of GFP-CaMKII in hippocampal neurons. Our data support a novel mechanism for targeting CaMKII to postsynaptic sites after neuronal activation. As such, CaMKII may form a scaffold that, in combination with other synaptic proteins, recruits and localizes additional proteins to the postsynaptic density. We discuss the potential function of CaMKII self-association as a tag of synaptic activity.</p>