[Postsynaptic density proteins related to the expression and modulation of synaptic plasticity].

One approach to elucidate the mechanism of synaptic plasticity, especially the postsynaptic mechanism, is the analysis of postsynaptic density (PSD). The PSD is an electron-dense cytoskeletal structure apposing the postsynaptic membrane, is a specific device for postsynaptic signal transmission, and attaches a number of molecules that are involved in postsynaptic signal transmission and its regulation. I review in this article the two groups of PSD proteins: Protein kinases (Ca2+/calmodulin-dependent protein kinase II, protein kinase C, mitogen-activated protein kinase, and tyrosine kinases) and molecules that work as messengers from the synapse to the nucleus (MSNs). Protein phosphorylation-dephosphorylation plays a pivotal role in the modulation of synaptic transmission, especially in the early phase of long-term potentiation (LTP). On the other hand, regulation of LTP at a late phase is governed by the new gene expression that is induced by synaptic inputs. For the altered gene expression, synaptic information must be transmitted from the synapse to the nucleus. I have started the search for the MSNs just recently. In this review, I describe several MSN candidates, especially NF-kappa B-like and I kappa B-like molecules.