CAMKII-BETA FUNCTIONS AS AN F-ACTIN TARGETING MODULE THAT LOCALIZES CAMKII-ALPHA BETA HETEROOLIGOMERS TO DENDRITIC SPINES/

Ca2+/calmodulin-dependent protein kinase II (CaMKII) is a serine/threo nine protein kinase that regulates long-term potentiation and other fo rms of neuronal plasticity. Functional differences between the neurona l CaMKII alpha and CaMKII beta isoforms are not yet known. Here, we us e green fluorescent protein-tagged (GFP-tagged) CaMKII isoforms and sh ow that CaMKII beta is bound to F-actin in dendritic spines and cell c ortex while CaMKII alpha is largely a cytosolic enzyme. When expressed together, the two isoforms form large heterooligomers, and a small fr action of CaMKII beta is sufficient to dock the predominant CaMKII alp ha to the actin cytoskeleton. Thus, CaMKII beta functions as a targeti ng module that localizes a much larger number of CaMKII alpha isozymes to synaptic and cytoskeletal sites of action.