Phosphorylation of the HCN channel auxiliary subunit TRIP8b is altered in an animal model of temporal lobe epilepsy and modulates channel function.
Temporal lobe epilepsy (TLE) is a prevalent neurological disorder with many patients experiencing poor seizure control with existing anti-epileptic drugs. Thus, novel insights into the mechanisms of epileptogenesis and identification of new drug targets can be transformative. Changes in ion channel function have been shown to play a role in generating the aberrant neuronal activity observed in TLE. Previous work demonstrates that hyperpolarization-activated cyclic nucleotide-gated (HCN) channels regulate neuronal excitability and are mislocalized within CA1 pyramidal cells in a rodent model of TLE. The subcellular distribution of HCN channels is regulated by an auxiliary subunit, tetratricopeptide repeat-containing Rab8b-interacting protein (TRIP8b), and disruption of this interaction correlates with channel mislocalization. However, the molecular mechanisms responsible for HCN channel dysregulation in TLE are unclear. Here we investigated whether changes in TRIP8b phosphorylation are sufficient to alter HCN channel function. We identified a phosphorylation site at residue Ser237 of TRIP8b that enhances binding to HCN channels and influences channel gating by altering the affinity of TRIP8b for the HCN cytoplasmic domain. Using a phosphospecific antibody, we demonstrate that TRIP8b phosphorylated at Ser237 is enriched in CA1 distal dendrites and that phosphorylation is reduced in the kainic acid model of TLE. Overall, our findings indicate that the TRIP8b-HCN interaction can be modulated by changes in phosphorylation and suggest that loss of TRIP8b phosphorylation may affect HCN channel properties during epileptogenesis. These results highlight the potential of drugs targeting posttranslational modifications to restore TRIP8b phosphorylation to reduce excitability in TLE.
['Foote|Kendall M|KM|0000-0002-8086-5674', 'Lyman|Kyle A|KA|', 'Han|Ye|Y|', 'Michailidis|Ioannis E|IE|', 'Heuermann|Robert J|RJ|', 'Mandikian|Danielle|D|', 'Trimmer|James S|JS|0000-0002-6117-3912', 'Swanson|Geoffrey T|GT|0000-0002-6645-9733', 'Chetkovich|Dane M|DM|']
D000595:Amino Acid Sequence D000818:Animals D001921:Brain D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 D003712:Dendrites D004195:Disease Models, Animal D004833:Epilepsy, Temporal Lobe D005260:Female D057809:HEK293 Cells D006801:Humans D015640:Ion Channel Gating D007608:Kainic Acid D008565:Membrane Proteins D008810:Mice, Inbred C57BL D000074401:Peroxins D010766:Phosphorylation D010768:Phosphoserine D021122:Protein Subunits D017207:Rats, Sprague-Dawley D015203:Reproducibility of Results
phosphorylation HCN TRIP8b epilepsy TLE ion channel neuronal excitability Ca2+/calmodulin-dependent protein kinase II (CaMKII) channelopathy protein–protein interaction