Alternative splicing in the variable domain of CaMKIIß affects the level of F-actin association in developing neurons
This article was published in International Journal of Clinical and Experimental Pathology, Volume 7, Issue 6, Pages 2963-2975.The published version is available at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4097261/.
Copyright © 2014 IJCEP.
The Ca2+/calmodulin (CaM)-dependent protein kinase II (CaMKII) ß has an essential function in dendritic spines via binding to and reorganization of the actin cytoskeleton during plasticity events not shared by CaMKIIa isoform. CaMKIIß and CaMKIIa isoforms have remarkable structural differences within the variable region. Three exons (E1, E3, and E4) are present in CaMKIIß but not in CaMKIIa gene. Four splice variants of CaMKIIß isoforms (CaMKIIß, ß, ße and ß'e) were discovered in embryonic and adult brains. Exons E1 (lacked in ße and ß'e) and E4 (lacked in ß' and ß'e) are subject to differential alternative splicing. We hypothesized that the sequences encoded by exons E1, E3, and/or E4 are involved in CaMKIIß-specific bundling to the F-actin cytoskeleton. We tested the colocalization and association of these CaMKIIß variants within an F-actin-rich structure (microspike) in CaMKIIa free embryonic day 18 (E-18) rat cortical neurons. Our results showed that CaMKIIß and CaMKIIß' containing exon E1 displayed an association with F-actin, while CaMKIIße and CaMKIIß'e lacking E1 did not. Moreover, CaMKIIß' lacking exon E4 but having E1 showed decreased actin bindingcapacity compared to WT CaMKIIß. This suggested E1 is required for the association between CaMKIIß and F-actin, while E4 assists CaMKIIß to associate with F-actin better. Thus, alternative splicing of CaMKIIß variants in developing neurons may serve as a developmental switch for actin cytoskeleton-associated isoforms and therefore correlated with dendritic arborization and synapse formation during LTP.