J Neurophysiol (April 1, 2003). 10.1152/jn.00837.2002
Submitted on Submitted 20 September 2002; accepted in final form 19 December 2002

KChIP1 and Frequenin Modify shal-Evoked Potassium Currents in Pyloric Neurons in the Lobster Stomatogastric Ganglion

 ¹Department of Neurobiology and Behavior, Cornell University, Ithaca, New York 14853; and  ²Millennium Pharmaceuticals, Cambridge, Massachusetts 02139

Zhang, Y., J. N. MacLean, W. F. An, C. C. Lanning, and R. M. Harris-Warrick. KChIP1 and Frequenin Modify shal-Evoked Potassium Currents in Pyloric Neurons in the Lobster Stomatogastric Ganglion. J. Neurophysiol. 89: 1902-1909, 2003. The transient potassium current (I_A) plays an important role in shaping the firing properties of pyloric neurons in the stomatogastric ganglion (STG) of the spiny lobster, Panulirus interruptus. The shal gene encodes I_A in pyloric neurons. However, when we over-expressed the lobster Shal protein by shal RNA injection into the pyloric dilator (PD) neuron, the increased I_A had somewhat different properties from the endogenous I_A. The recently cloned K-channel interacting proteins (KChIPs) can modify vertebrate Kv4 channels in cloned cell lines. When we co-expressed hKChIP1 with lobster shal in Xenopus oocytes or lobster PD neurons, they produced A-currents resembling the endogenous I_A in PD neurons; compared with currents evoked by shal alone, their voltage for half inactivation was depolarized, their kinetics of inactivation were slowed, and their recovery from inactivation was accelerated. We also co-expressed shal in PD neurons with lobster frequenin, which encodes a protein belonging to the same EF-hand family of Ca²⁺ sensing proteins as hKChIP. Frequenin also restored most of properties of the shal-evoked currents to those of the endogenous A-currents, but the time course of recovery from inactivation was not corrected. These results suggest that lobster shal proteins normally interact with proteins in the KChIP/frequenin family to produce the transient potassium current in pyloric neurons.