Proceedings of the National Academy of Sciences, Vol 89, 1133-1137, Copyright © 
1992 by National Academy of Sciences 


Overexpression of an Aplysia Shaker K+ Channel Gene Modifies the Electrical 
Properties and Synaptic Efficacy of Identified Aplysia Neurons

B Kaang, PJ Pfaffinger, SGN Grant, ER Kandel and Y Furukawa 

Although potassium channels play a variety of roles in shaping the electrical 
properties of neurons, little is known about how these channels are constituted 
in neurons. To examine the assembly and physiological function of A-type K+ 
channels in mature differentiated neurons, we have developed a highly efficient 
gene transfer method for Aplysia neurons that has allowed us to express about 
107 copies of the cloned Aplysia Shaker (Sh) K+ channel (AK01a) in single 
identified cells. We find that expression of AK01a phenocopies one of the native 
transient K+ currents (IAdepol), suggesting that the native channel carrying 
IAdepol is assembled as a homooligomer of AK01a. Overexpression of AK01a has 
substantial effect on the action potential, shortening its duration, enhancing 
its hyperpolarizing afterpotential, and depressing by more than half the amount 
of transmitter release by the action potential from the terminals. Thus, the 
AK01a channel not only contributes to the firing properties within a given 
neuron but also can regulate the signaling between interconnected cells.