Immunocytochemical localization of calcium/calmodulin-dependent protein kinase II in rat brain.

Abstract

Calcium/calmodulin-dependent protein kinase II (CaM kinase II) is a prominent enzyme in mammalian brain capable of phosphorylating a variety of substrate proteins. In the present investigation, the subcellular and regional distribution of CaM kinase II has been studied by light and electron microscopic immunocytochemistry using an antibody that recognizes the Mr 50,000 and 60,000/58,000 subunits of the enzyme. Light microscopy demonstrates strong immunoreactivity in neuronal somata and dendrites and weak immunoreactivity in axons. Electron microscopy, in addition to confirming light microscopic observations, reveals moderate immunoreactivity in spines and weak immunoreactivity ii nerve terminals. An accumulation of immunoreaction product is also present on postsynaptic densities. The presence of CaM kinase II in diverse structures throughout the neuron supports the view that this enzyme may be involved in mediating a variety of calcium-dependent physiological processes. CaM kinase II immunoreactivity is present in neurons throughout the brain, but a marked regional variation in the strength of the immunoreactivity exists. Overall, there is a gradient of staining intensity with the strongest immunoreactivity in the telencephalon and the weakest in the myelencephalon. The most heavily labeled regions of the telencephalon are the hippocampal formation, lateral septum, cortical regions, neostriatum, and amygdaloid complex.

Differential Inactivation of Postsynaptic Density‐Associated and Soluble Ca2+/Calmodulin‐Dependent Protein Kinase II by Protein Phosphatases 1 and 2A

“…Ischemic conditions also trigger a rapid translocation of CaMKII to synaptic junctions (Hu and Wieloch, 1995). Thus, under physiological conditions the majority of CaMKII appears to be in soluble fractions, although a fraction is almost certainly PSD-associated, as judged by immunoelectron microscopy (Ouimet et al, 1984;Fukunaga et al, 1988). Indeed, Triton X-100-insoluble fractions, which include PSDs, rapidly prepared from whole forebrain or from hippocampal slices incubated under physiological conditions in vitro, contain only '--15% of the total CaMKII (S. Strack and R. J. Colbran, unpublished data).…”

Visualization of the Distribution of Autophosphorylated Calcium/Calmodulin-Dependent Protein Kinase II after Tetanic Stimulation in the CA1 Area of the Hippocampus

“…C aM K II is expressed at unusually high levels in the forebrain and cerebellum, making up ϳ2% of total protein in the hippocampus. Approximately half of the kinase behaves as a soluble enzyme after homogenization and can be visualized in the cytosol of neuronal cell bodies (Ouimet et al, 1984;Erondu and Kennedy, 1985;Apperson et al, 1996). In addition, a large portion is particulate and is concentrated at synapses in both presynaptic and postsynaptic compartments Ouimet et al, 1984;Benfenati et al, 1992).…”

Calcium/Calmodulin-Dependent Protein Kinase II

“…10-fold between postnatal days 1 and 21 [31]. In adult rat brain, the highest levels of CaMkinase II are found in the telencephalon regions (hippocampus, lateral septum, cortex, neostriatum, amygdaloid), with much lower activity in the cerebellum, diencephalon, mesencephalon, pons and medulla [9,38]. The ratio of subunits also varies between the different regions, with a and , subunits present in a 4: 1 ratio in rat forebrain and in a 1:4 ratio in cerebellum [12,39].…”

“…Within the neuron, CaMkinase II appears to be distributed in the spines, somata, axons, dendrites and nerve terminal, with little in the nuclei [38]. In the dendrites of forebrain the kinase is particularly concentrated in the postsynaptic density, where the a subunit is the major postsynaptic density protein of 50 kDa, constituting 30 50 o of the total protein [40][41][42].…”