Ionotropic glutamate receptors mediate fast excitatory neurotransmission. Heteromultimerization of glutamate receptor subunits determines critical channel properties which in turn can influences cell signaling processes. Subunit oligomerization, however, occurs only within glutamate receptor subfamilies, suggesting a protein domain that determines subunit-specific assembly . The objective of these experiments is to define molecular mechanisms that determine oligomerization of glutamate receptor subunits. This fragment also exerts a dominant negative effect on AMPA, but not NMDA, current expression. These data, among others, demonstrate that the amino terminus of AMPA receptors is involved in subunit association and may be critical for assembly. Experiments proposed herein are designed to complement these results by answering several specific questions. Specific Aim #1 applies the powerful yeast- two-hybrid approach results by answering several specific questions. Specific Aim #1 applies the powerful yeast-two-hybrid approach to define and characterize minimal regions of subunit association. Specific Aim #2 answers the question of whether glycosylation influences subunit association in AMPA receptors. Analytical ultracentrifugation experiments in Specific Aim #3 are designed to determine the molecular weight, stoichiometry, and association properties of amino-terminal fragments, which have been shown to self-associated in co- inmmunoprecipitation experiments. Finally, Specific Aim #4 is designed to determine whether AMPA receptor assembly occurs in the endoplasmic reticulum or in another intracellular compartment. In combination with previous data, these experiments will provide a comprehensive description of AMPA receptor biogenesis.