Characterization of Putative Protein-Protein Interactions of the Major Histocompatibility Complex Class I Cytoplasmic Domain in the Mouse Hippocampus

Abstract

Major histocompatibility complex class I (MHCI) proteins belong to a large, polymorphic gene family known for their role in mammalian adaptive immunity. MHCI molecules have also been found to play a critical role in the developing and healthy central nervous system. Localized to neuronal synapses, MHCI has been shown to inhibit hippocampal NMDA receptor function. It has also been linked to synaptic plasticity and synaptic density. However, the mechanisms of MHCI’s activity in the nervous system remain undefined. Preliminary research has indicated that the cytoplasmic domain (CD) of MHCI contains embedded putative ligands of an extensive family of protein-protein interaction motifs designated PDZ domains. To investigate the hypothesis that molecular mediators of MHCI function in the brain may interact through short binding motifs in the intracellular domain, multiple binding assays were completed to probe for prospective binding partners. The molecular scaffolding protein PSD-95 and PP1 regulatory sub-unit spinophilin were both identified. To characterize the interactions of these proteins with MHCI the putative PDZ motifs in the CD were subjected to site-directed mutagenesis. Disrupted binding in mutations studies will help validate ligand motifs in the CD and identify functionally significant interaction between MHCI and the molecular mediators of its neuronal activity.