Acute Rheumatism

Abstract

<h3>Summary</h3> Signal transduction at vertebrate excitatory synapses involves the activity of ionotropic glutamate receptors, including the AMPA (α-amino-3-hydroxy-5-methyl-4-isoaxazole propionate) receptor. Technical advances in cryo-electron microscopy have brought a slew of full-length structures of AMPA receptors, on their own and in combination with auxiliary subunits. These structures illustrate a wide range of conformations, indicating that individual domains might undergo substantial lateral and rotational motions during gating. Here, we used bifunctional methanethiosulfonate cross-linkers to calibrate the conformations that occur in functional AMPA receptors both in the presence and absence of the auxiliary subunit Stargazin. Our data indicate that receptors without auxiliary subunits have considerably more conformational freedom and can get trapped in relaxed conformations. In contrast, Stargazin maintains both activated and desensitized receptors in compact arrangements. Thus, auxiliary subunits not only change the kinetics and trafficking of receptors, but also restrict their structural dynamics.