Expression and subcellular localization of multifunctional calmodulin-dependent protein kinases-I, -II and -IV are altered in rat hippocampal CA1 neurons after induction of long-term potentiation

Long-term potentiation (LTP) is considered to be associated with an increas e in expression as well as activity of Ca2+/calmodulin-dependent protein ki nases (CaMKs). LTP-induced and control hippocampal slices were studied by i mmunohistochemical and electronmicroscopic analyses using anti-CaMK-I, -II and -IV antibodies. All three kinases were demonstrated to increase their e xpression in CA1 neurons. CaMK-I was shown to mainly localize in the cytopl asm of the control and LTP-induced neurons, and a significant increase of i mmunoreactivity was observed in the latter neurons. A part of CaMK-I was fo und to translocate to the nuclei of LTP-induced hippocampal CA1 neu ro ns. Direct evidence of the translocation of CaMK-II from cytoplasm to nuclei in LTP was demonstrated by immuno-electronmicroscopy. A significant increase in expression of CaMK-IV in the nuclei was also observed. Our data suggest that all the th ree CaMKs were actively involved in nuclear Ca2+-signaling in LTP. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.