GHB analogs confer neuroprotection through specific interaction with the CaMKIIα hub domain

Ca2+/calmodulin-dependent protein kinase II alpha subunit (CaMKII alpha) isa key neuronal signaling protein and an emerging drug target. The central hub domain regulates the activity of CaMKII alpha by organizing the holoenzyme complex into functional oligomers, yet pharmacological modulation of the hub domain has never been demonstrated. Here, using a combination of photoaffinity labeling and chemical proteomics, we show that compounds related to the natural substance gamma-hydroxybutyrate (GHB) bind selectively to CaMKII alpha. By means of a 2.2-A x-ray crystal structure of ligand-bound CaMKII alpha hub, we reveal the molecular details of the binding site deep within the hub. Furthermore, we show that binding of GHB and related analogs to this site promotes concentration-dependent increases in hub thermal stability believed to alter holoenzyme functionality. Selectively under states of pathological CaMKII alpha activation, hub ligands provide a significant and sustained neuroprotection, which is both time and dose dependent. This is demonstrated in neurons exposed to excitotoxicity and in a mouse model of cerebral ischemia with the selective GHB analog, HOCPCA (3-hydroxycyclopent-1-enecarboxylic acid). Together, our results indicate a hitherto unknown mechanism for neuroprotection by a highly specific and unforeseen interaction between the CaMKII alpha hub domain and small molecule brain-penetrant GHB analogs. This establishes GHB analogs as powerful tools for investigating CaMKII neuropharmacology in general and as potential therapeutic compounds for cerebral ischemia in particular

Automated summary

This study demonstrates the selective binding of compounds related to GHB to CaMKIIα, leading to increased thermal stability of the hub and providing neuroprotection, particularly under pathological conditions. This unexpected interaction establishes GHB analogs as powerful tools for investigating CaMKII neuropharmacology in general and as potential therapeutic compounds for cerebral ischemia.