TY - JOUR
T1 - Identifying mutation hotspots reveals pathogenetic mechanisms of KCNQ2 epileptic encephalopathy
AU - Zhang, Jiaren
AU - Kim, Eung Chang
AU - Chen, Congcong
AU - Procko, Erik
AU - Pant, Shashank
AU - Lam, Kin
AU - Patel, Jaimin
AU - Choi, Rebecca
AU - Hong, Mary
AU - Joshi, Dhruv
AU - Bolton, Eric
AU - Tajkhorshid, Emad
AU - Chung, Hee Jung
N1 - We thank Dr. Claudio Grosman (University of Illinois at Urbana-Champaign) for comments on the manuscript and discussion on the results for Dr-VSP-mediated Kv7 current suppression. We also acknowledge computing resources provided by PRAC allocation at Blue Waters of National Center for Supercomputing Applications (ACI-1713784 to E.T.), and Extreme Science and Engineering Discovery Environment (grant TG-MCA06N060 to E.T.). We would also like to acknowledge Beckman Institute Graduate Fellowship for supporting S.P. This research was supported by the Research Project Grant #R01NS083402 from the NIH National institute of Neurological Disorders and Stroke (PI: Chung), Carver Young Investigator Grant Award #11–38870 from Roy J. Carver Charitable Trust (PI: Chung), Targeted Research Initiative for Severe Symptomatic Epilepsies Grant #C4107 from Epilepsy Foundation (PI: Chung). National Institute of General Medical Sciences of the National Institutes of Health under awards P41-GM104601 (PI: Tajkhorshid) and R01-GM123455 (PI: Tajkhorshid).
PY - 2020/12/1
Y1 - 2020/12/1
N2 - Kv7 channels are enriched at the axonal plasma membrane where their voltage-dependent potassium currents suppress neuronal excitability. Mutations in Kv7.2 and Kv7.3 subunits cause epileptic encephalopathy (EE), yet the underlying pathogenetic mechanism is unclear. Here, we used novel statistical algorithms and structural modeling to identify EE mutation hotspots in key functional domains of Kv7.2 including voltage sensing S4, the pore loop and S6 in the pore domain, and intracellular calmodulin-binding helix B and helix B-C linker. Characterization of selected EE mutations from these hotspots revealed that L203P at S4 induces a large depolarizing shift in voltage dependence of Kv7.2 channels and L268F at the pore decreases their current densities. While L268F severely reduces expression of heteromeric channels in hippocampal neurons without affecting internalization, K552T and R553L mutations at distal helix B decrease calmodulin-binding and axonal enrichment. Importantly, L268F, K552T, and R553L mutations disrupt current potentiation by increasing phosphatidylinositol 4,5-bisphosphate (PIP2), and our molecular dynamics simulation suggests PIP2 interaction with these residues. Together, these findings demonstrate that each EE variant causes a unique combination of defects in Kv7 channel function and neuronal expression, and suggest a critical need for both prediction algorithms and experimental interrogations to understand pathophysiology of Kv7-associated EE.
AB - Kv7 channels are enriched at the axonal plasma membrane where their voltage-dependent potassium currents suppress neuronal excitability. Mutations in Kv7.2 and Kv7.3 subunits cause epileptic encephalopathy (EE), yet the underlying pathogenetic mechanism is unclear. Here, we used novel statistical algorithms and structural modeling to identify EE mutation hotspots in key functional domains of Kv7.2 including voltage sensing S4, the pore loop and S6 in the pore domain, and intracellular calmodulin-binding helix B and helix B-C linker. Characterization of selected EE mutations from these hotspots revealed that L203P at S4 induces a large depolarizing shift in voltage dependence of Kv7.2 channels and L268F at the pore decreases their current densities. While L268F severely reduces expression of heteromeric channels in hippocampal neurons without affecting internalization, K552T and R553L mutations at distal helix B decrease calmodulin-binding and axonal enrichment. Importantly, L268F, K552T, and R553L mutations disrupt current potentiation by increasing phosphatidylinositol 4,5-bisphosphate (PIP2), and our molecular dynamics simulation suggests PIP2 interaction with these residues. Together, these findings demonstrate that each EE variant causes a unique combination of defects in Kv7 channel function and neuronal expression, and suggest a critical need for both prediction algorithms and experimental interrogations to understand pathophysiology of Kv7-associated EE.
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U2 - 10.1038/s41598-020-61697-6
DO - 10.1038/s41598-020-61697-6
M3 - Article
C2 - 32179837
AN - SCOPUS:85081989194
SN - 2045-2322
VL - 10
JO - Scientific reports
JF - Scientific reports
IS - 1
M1 - 4756
ER -