Analysis of pThr 286-CaMKII and CaMKII immunohistochemistry in the hippocampus of patients with temporal lobe epilepsy

Abstract

Ca 2+/calmodulin-dependent protein kinase II (CaMKII) phosphorylates a variety of neuronal proteins, thereby, coordinating responses to changes of intracellular Ca 2+ concentrations. Autophosphorylation at threonine 286 generates an autonomously active form of CaMKII (pThr 286-CaMKII), thus prolonging responses to transient increases in Ca 2+. Our previous studies in hippocampi of temporal lobe epilepsy (TLE) patients revealed a significant up-regulation of CaMKII in dentate granule cells (DGCs) of specimens with Ammon's horn sclerosis (AHS). However, the functional status of the up-regulated enzyme remained unclear. Therefore, we performed double immunofluorescence staining for CaMKII and pThr 286-CaMKII in hippocampi of TLE patients and controls. Furthermore, we analyzed the ratio of the relative fluorescence intensities pThr 286-CaMKII: CaMKII in DGCs. CaMKII immunoreactivity was significantly increased in DGC bodies and their proximal dendrites in AHS. In contrast, immunostaining for pThr 286-CaMKII was localized to the DGC bodies, revealing similar labeling intensities in all TLE and control specimens, and was not observed in the dendritic compartment of DGCs. Analysis of the ratio of the relative fluorescence intensities pThr 286-CaMKII:CaMKII in DGC bodies revealed a significantly reduced ratio in AHS compared to lesion-associated TLE and controls. Thus, up-regulation of total CaMKII in DGCs of AHS specimens is not paralleled by an increase of its autonomously active form.