When Laura Moreno Wasielewski watched kainate receptors respond to a chemical nudge at Ruhr University Bochum, she saw something no one had expected—just two subunits, the GluK5 pair, could flip the switch and open the entire ion channel, even though four subunits make up the complex. This discovery, made alongside Professor Andreas Reiner and a transatlantic team including Professor Joshua Levitz at Weill Cornell Medicine, challenges long-held assumptions about how glutamate receptors—key players in brain signaling—actually work. These receptors, specifically the GluK2/GluK5 kainate heteromer, are among the most common in the human brain, yet their precise activation mechanism remained a mystery. Using 5-iodowillardiine, a compound that binds exclusively to GluK5 subunits, Wasielewski demonstrated that the receptor could be driven into a permanently open state, proving that activation doesn’t require all four subunits to be engaged.
For years, scientists believed the GluK2 subunits were the primary drivers of channel opening due to their closer structural link to the ion pore. But cryo-electron microscopy images from the Levitz lab revealed a hidden choreography: when glutamate binds to GluK5, it triggers movement in the neighboring GluK2 subunits, effectively using them as mechanical levers to open the gate. This unexpected cooperation explains how the less optimally positioned GluK5 subunits still manage to control the channel. Even more striking, the team found that partial binding—only two of four subunits occupied—activates the receptor without triggering desensitization, a self-shutdown process that typically follows full activation. That means the receptor can sustain long-lasting electrical currents, a rare trait with profound implications for how neurons process and modulate signals over time.
Another surprise emerged: a tight interaction between the two opposing GluK5 subunits, a feature never seen in related AMPA or other kainate receptors. This interface isn’t just structural flair—it directly influences the receptor’s unusually slow deactivation, which lasts about 10 times longer than in other kainate receptors. That sluggish off-switch could allow synaptic signals to linger, fine-tuning communication between neurons. Because GluK2 and GluK5 have different glutamate affinities, these partially bound, non-desensitizing states may occur naturally in the brain, suggesting this mechanism isn’t just a lab curiosity but a potential cornerstone of neural modulation. With the new structural blueprints in hand, researchers can now design experiments to probe how this slow signaling shapes learning, memory, or even neurological disorders. As Reiner notes, the GluK5-GluK5 interface offers a new experimental handle—one that might one day lead to targeted therapies for conditions where brain signaling goes awry.