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

Abstract

Cal/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 was studied by light microscopic and EM immunocytochemistry using an antibody that recognizes the MW 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. EM, in addition to confirming light microscopic observations, reveals moderate immunoreactivity in spines and weak immunoreactivity in 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 Ca-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.