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THE COUNCIL FOR TOBACCO RESEARCH-U.S.A.. INC. 900 TISIRD AVENUE NEW YORK. N.Y. 10022 Memorandum To: Dr. H.McAllister and Staff Fran: D.H.Ford Re: Site visit with Dr. James Trimmer, SUNY at Stoney Brcok,NY, May 4, 1994. Grant No.3466R1 entitled "Genetic isolation and reccnstituti cn of brain potassium channel ccmplexes." Coal: To determine the roles of the various subunits which form a TF channel in relation the' physiological properties which they provide for the channel in neuronal, striated muscle and cardiac muscle fibers. Progress: In a recent publication (Nerve growth factor regulates the abundance and distributi_cn of K~L' channels in PC12 cells', Sharma, et al. J.Ce1l-Bio1. 1.23:1335-4:3,1993) Dr. Trimmer reported that NGF increased the abundance of the delayed rectifier K+ channel subtype in PC12 cells f ourf old. In undiiTerentiated ce l ls (in the absence of NGF), the Kv2. 1 K+ channel was localized in the cell membrane at sites of cell contact. After exposure to NGF, the channel sites were observed to be in the neuritic 'growth cones. Other progress is described in 3 recent manuscripts submitted to JBC, J.Neurosci. and to Neuron. In the JB'C paper Dr.Timmer describes the expression of the rat Kv2.1 K+ channel polypeptide by transfection in mammalian COS-1 cells, which expressed a Kv2.1, peptide with a molecular weight of 108kD as canpared to the core size polypeptide of 95kD predicted fran the deduced primary sequence and of the pKv2.1 synthesized in cell free or Xenopus oocyte systems. The increase in size of pKv2.1 in the COS-1 cells was apparently due to a posttranslational modi.fication which occurred early (t 1/2 = 5 min)L during the biosynthetic transport through the endoplasmic reticulum. The increased size appears to be due to ph osphory lati on of the core peptide. In the paper to J.of Neurosci. Dr. Trimmer and colleages note that voltage-gated K+ channels play an essential role in controlling action potential duration, amplitude and frequency and that elec~rical activity can in turn regulate neuronal gene expression for the K channel. Thus, membrane depolarization was observed to specifically and rapidly inhibit Kvl.5 voltage-gated K+ channel gene expressicn. Since this would permit a long-term membrane depolarization, this could lead to an increase in neuronal excitability.and enhance synaptic transmission in such a way as to promote seizure activity and epilepsy. In the manuscript submitted to ($euron, Dr. Trimmer reports that thyroid releasing hormone (TRH) enhances neurcnal excitability by inhibiting K+ channel gene exvression for the Kv2.1 K+ channel, but has no effect on the Kvl.4 K channel or on the;xIDcalcium channel mRNA. The mRNA for the Kv1. 5 K+ channel was a ls o down regulated by TRH. Thus, it appears that the various subtypes of the K+ channel illustrate the same type of diversity in response to various ligands as do a wide variety of receptors. Canment: An active program in which progess appears to be moving rao3ly in unraveling the many physiologic roles played by K+

-2- channels. It is also beginning to appear that the roles may vary according to the cell. type in which the channels are located. Further, their distribution in neurons may well vary in a manner similar to Ca++ channels, being absent in axons, being moderately present on cell body membranes and with a much higher concer,tration along the dendrites wherein the highest concentrations are on the dendritic spin;a_,. This would be logical inasmuch as the opening of the Kt channels appears to be associated with the clcsW:S~ of the Ca++ channel to return the membrane to the repolarized state. This is an interesting and exciting program directed by a young enthusiastic well. informed investigator. DHF