The Drosophila Shaker gene codes for a distinctive K+ current in a subset of neurons.
A transient K+ current coded by the Shaker gene was identified in muscle and expressed in Xenopus oocytes by injecting cRNA transcribed from a cloned cDNA. The Shaker current has not previously been identified in neurons. Mutational analysis now reveals that in neurons, Shaker is required for expression of a very rapidly inactivating K+ current with a depolarized steady-state inactivation curve. Together, these properties distinguish the Shaker-coded current from similar fast transient K+ currents coded by other genes. The Sh5 mutation further enhanced the depolarization of the Shaker current steady-state inactivation curve. Deletion of the Shaker gene completely removes the transient K+ current from a small percentage of neurons (15%) in a mixed population, and removes a portion of the whole-cell current in about 35% of neurons. The remaining 50% of neurons were apparently unaffected by deletion of the Shaker gene. The unique combination of rapid inactivation and depolarized steady-state inactivation of the Shaker current may reflect a unique functional role for this current in the nervous system such as the rapid repolarization of action potentials.
Baker
K
K
Department of Anatomy and Neurobiology, Washington University School of Medicine, St Louis, Missouri 63110.
Salkoff
L
L
D000200:Action Potentials; D000818:Animals; D015139:Blotting, Southern; D002872:Chromosome Deletion; D003001:Cloning, Molecular; D004330:Drosophila / Q000235:genetics; D005796:Genes; D005838:Genotype; D009474:Neurons / Q000166:cytology / Q000502:physiology*; D015221:Potassium Channels / Q000502:physiology*
D015221:Potassium Channels