CaMKII, calcium/calmodulin dependent protein kinase, is an active kinase in the cell that phosphorylates a number of substrates including several cytoskeletal and signaling proteins. In addition to kinase activity, the β isoform of CaMKII also contains an F-actin binding region. We recently identified a new F-actin rich structure in developing cortical neurons that endogenous CaMKIIβ bound. In nonneuronal cells and dendrite spines of hippocampal neurons where an interaction between CaMKIIβ and F-actin has been identified, CaMKIIβ was involved in regulating the differentiation of dendrite spines and formation of synapses. In this study, we took advantage of the temporal and spatial regulation of CaMKII isoforms to reveal a specific role for CaMKIIβ in binding and stability of a novel F-actin rich structure. We used FRAP and colocalization assays in this CaMKIIβ rich system to demonstrate a structural, rather than enzymatic, role of CaMKIIβ. In this addendum, we further discuss the significance of this study and the possible implication to the field.