Structural basis for the interaction between dynein light chain 1 and the glutamate channel homolog GRINL1A

Human dynein light chain 1 (DYNLL1) is a dimeric 89-residue protein that is known to be involved in cargo binding within the dynein multiprotein complex. Over 20 protein targets, of both cellular and viral origin, have been shown to interact with DYNLL1, and some of them are transported in a retrograde manner along microtubules. Using DYNLL1 as bait in a yeast two-hybrid screen with a human heart library, we identified GRINL1A (ionotropic glutamate receptor N-methyl-D-aspartate-like 1A), a homolog of the ionotropic glutamate receptor N-methyl D-aspartate, as a DYNLL1 binding partner. Binding of DYNLL1 to GRINL1A was also demonstrated using GST fusion proteins and pepscan membranes. Progressive deletions allowed us to narrow the DYNLL1 binding region of GRINL1A to the sequence REIGVGCDL. Combining these results with NMR data, we have modelled the structure of the GRINL1A-DYNLL1 complex. By analogy with known structures of DYNLL1 bound to BCL-2-interacting mediator (BIM) or neuronal nitric oxide synthase (nNOS), the GRINL1A peptide also adopts an extended beta-strand conformation that expands the central beta-sheet within DYNLL1. Structural comparison with the nNOS-DYNLL1 complex reveals that a glycine residue of GRINL1A occupies the conserved glutamine site within the DYNLL1 binding groove. Hence, our data identify a novel membrane-associated DYNLL1 binding partner and suggest that additional DYNLL1-binding partners are present near this glutamate channel homolog.