TitleN-methyl-D-aspartate receptor subunits are non-myosin targets of myosin regulatory light chain.
Publication TypeJournal Article
Year of Publication2009
AuthorsBajaj G, Zhang Y, Schimerlik MI, Hau AM, Yang J, Filtz TM, Kioussi C, Ishmael JE
JournalJ Biol Chem
Date Published2009 Jan 09
KeywordsAmino Acid Sequence, Animals, Brain, Calmodulin, Cell Line, Cell Membrane, Humans, Magnesium, Molecular Sequence Data, Muscle, Smooth, Myosin Light Chains, Myosin Type II, Protein Binding, Protein Isoforms, Protein Subunits, Rats, Receptors, N-Methyl-D-Aspartate, Sequence Alignment

Excitatory synapses contain multiple members of the myosin superfamily of molecular motors for which functions have not been assigned. In this study we characterized the molecular determinants of myosin regulatory light chain (RLC) binding to two major subunits of the N-methyl-d-aspartate receptor (NR). Myosin RLC bound to NR subunits in a manner that could be distinguished from the interaction of RLC with the neck region of non-muscle myosin II-B (NMII-B) heavy chain; NR-RLC interactions did not require the addition of magnesium, were maintained in the absence of the fourth EF-hand domain of the light chain, and were sensitive to RLC phosphorylation. Equilibrium fluorescence spectroscopy experiments indicate that the affinity of myosin RLC for NR1 is high (30 nm) in the context of the isolated light chain. Binding was not favored in the context of a recombinant NMII-B subfragment one, indicating that if the RLC is already bound to NMII-B it is unlikely to form a bridge between two binding partners. We report that sequence similarity in the "GXXXR" portion of the incomplete IQ2 motif found in NMII heavy chain isoforms likely contributes to recognition of NR2A as a non-myosin target of the RLC. Using site-directed mutagenesis to disrupt NR2A-RLC binding in intact cells, we find that RLC interactions facilitate trafficking of NR1/NR2A receptors to the cell membrane. We suggest that myosin RLC can adopt target-dependent conformations and that a role for this light chain in protein trafficking may be independent of the myosin II complex.

Alternate JournalJ. Biol. Chem.
PubMed ID18945678
PubMed Central IDPMC2613636
Grant ListP30-ES000210 / ES / NIEHS NIH HHS / United States
R01AR054406 / AR / NIAMS NIH HHS / United States