Functional consequences of a Na+ channel mutation causing hyperkalemic periodic paralysis.
Hyperkalemic periodic paralysis (HYPP), one of several inheritable myotonic diseases, results from genetic defects in the human skeletal muscle Na+ channel. In some pedigrees, HYPP is correlated with a single base pair substitution resulting in a Met replacing Thr704 in the fifth transmembrane segment of the second domain. This region is totally conserved between the human and rat channels. We have introduced the human mutation into the corresponding region of the rat muscle Na+ channel cDNA and expressed it in human embryonic kidney 293 cells. Patch-clamp recordings show that this mutation shifts the voltage dependence of activation by 10-15 mV in the negative direction. The shift results in a persistent Na+ current that activates near -70 mV; this phenomenon could underlie the abnormal muscle activity observed in patients with HYPP.
Cummins
T R
TR
Interdepartmental Neuroscience Program, Yale University School of Medicine, New Haven, Connecticut 06510.
Zhou
J
J
Sigworth
F J
FJ
Ukomadu
C
C
Stephan
M
M
Ptácek
L J
LJ
Agnew
W S
WS
D000595:Amino Acid Sequence; D001483:Base Sequence; D002461:Cell Line, Transformed; D004594:Electrophysiology; D005110:Extracellular Space / Q000378:metabolism; D006706:Homeostasis; D006801:Humans; D006863:Hydrogen-Ion Concentration; D006947:Hyperkalemia / Q000235:genetics*; D007700:Kinetics; D008969:Molecular Sequence Data; D009154:Mutation; D015345:Oligonucleotide Probes / Q000235:genetics; D010243:Paralysis / Q000235:genetics*; D010507:Periodicity; D011188:Potassium / Q000378:metabolism; D015222:Sodium Channels / Q000235:genetics* / Q000502:physiology
D015345:Oligonucleotide Probes; D015222:Sodium Channels; D011188:Potassium