Calmodulin Modification of NMDA Receptors

Abstract

Using approaches of molecular biology, biochemistry, and electrophysiology, we have recently discovered the interaction between calmodulin and NMDA receptor ion channels (1). We demonstrated that calmodulin specifically binds to two distinct sites (CBS1 and CBS2) localized in the C-terminus of the NR1 subunits, causing a fourfold decrease in the channel open probability (1). The CBS1 (K _d for calmodulin: 80 nM) covers most of the C-terminal region that is upstream to the C1 cassette, designated C0, and common to all NR1 splice variants (NR1a-h). The CBS2 (K _d for calmodulin: 4 nM) is downstream of the CBS1 and located in the C1 exon cassette, which is subject to alternative splicing. We further showed that calmodulin binding to the CBS1 is responsible for an important property of NMDA receptors, Ca²⁺-dependent inactivation (2). More studies are expected to clarify further the biological significance and molecular mechanisms of interaction between calmodulin and NMDA receptors. This chapter is a stepwise description of our laboratory protocols used in studying the modulation of NMDA receptors by calmodulin. We hope that the protocols will help people investigate the issue and evaluate the literature in this field.