CRL4A CRBN E3 ubiquitin ligase restricts BK channel activity and prevents epileptogenesis

Ion channels regulate membrane excitation, and mutations of ion channels often cause serious neurological disorders including epilepsy. Compared with extensive analyses of channel protein structure and function, much less is known about the fine tuning of channel activity by post-translational modification. Here we report that the large conductance, Ca 2+ - and voltage-activated K + (BK) channels are targeted by the E3 ubiquitin ligase CRL4A CRBN for polyubiquitination and retained in the endoplasmic reticulum (ER). Inactivation of CRL4A CRBN releases deubiquitinated BK channels from the ER to the plasma membrane, leading to markedly enhanced channel activity. Mice with CRL4A CRBN mutation in the brain or treated with a CRL4A CRBN inhibitor are very sensitive to seizure induction, which can be attenuated by blocking BK channels. Finally, the mutant mice develop spontaneous epilepsy when aged. Therefore, ubiquitination of BK channels before their cell surface expression is an important step to prevent systemic neuronal excitability and epileptogenesis.