Biochemical characterization of sporadic/familial hemiplegic migraine mutations.
Sporadic hemiplegic migraine type 2 (SHM2) and familial hemiplegic migraine type 2 (FHM2) are rare forms of hemiplegic migraine caused by mutations in the Na(+),K(+)-ATPase α2 gene. Today, more than 70 different mutations have been linked to SHM2/FHM2, randomly dispersed over the gene. For many of these mutations, functional studies have not been performed. Here, we report the functional characterization of nine SHM2/FHM2 linked mutants that were produced in Spodoptera frugiperda (Sf)9 insect cells. We determined ouabain binding characteristics, apparent Na(+) and K(+) affinities, and maximum ATPase activity. Whereas membranes containing T345A, R834Q or R879W possessed ATPase activity significantly higher than control membranes, P796S, M829R, R834X, del 935-940 ins Ile, R937P and D999H membranes showed significant loss of ATPase activity compared to wild type enzyme. Further analysis revealed that T345A and R879W showed no changes for any of the parameters tested, whereas mutant R834Q possessed significantly decreased Na(+) and increased K(+) apparent affinities as well as decreased ATPase activity and ouabain binding. We hypothesize that the majority of the mutations studied here influence interdomain interactions by affecting formation of hydrogen bond networks or interference with the C-terminal ion pathway necessary for catalytic activity of Na(+),K(+)-ATPase, resulting in decreased functionality of astrocytes at the synaptic cleft expressing these mutants.
Department of Pharmacology and Toxicology 149, Radboud University Medical Centre, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands. Electronic address: Karl.Weigand@radboudumc.nl.
Karl M
KM
Weigand
Department of Biochemistry 286, Radboud University Medical Centre, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands. Electronic address: H.Swarts@ncmls.ru.nl.
Herman G P
HG
Swarts
Department of Pharmacology and Toxicology 149, Radboud University Medical Centre, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands. Electronic address: Frans.Russel@radboudumc.nl.
Frans G M
FG
Russel
Department of Pharmacology and Toxicology 149, Radboud University Medical Centre, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands. Electronic address: Jan.Koenderink@radboudumc.nl.
Jan B
JB
Koenderink
D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000235:genetics / Q000378:metabolism; D020022:Genetic Predisposition to Disease; D006860:Hydrogen Bonding; D020325:Migraine with Aura / Q000201:enzymology / Q000235:genetics*; D008958:Models, Molecular; D009154:Mutation; D010042:Ouabain / Q000378:metabolism; D061987:Sf9 Cells; D000254:Sodium-Potassium-Exchanging ATPase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D018411:Spodoptera / Q000235:genetics
D010042:Ouabain; D000254:Sodium-Potassium-Exchanging ATPase
ATP1A2; Alpha 2 isoform; Baculovirus expression system; FHM2; Familial hemiplegic migraine; Na(+),K(+)-ATPase