Differential Expression and Targeting of K+ Channel Genes in the Lobster Pyloric Central Pattern Generatora

Abstract: A molecular analysis of motor pattern generation is an essential complement to electrophysiological and computational investigations. In arthropods, A‐channels are posttranslationally modified multimeric proteins containing Shaker family α‐subunits that may interact with β‐subunits, γ‐subunits, and other auxiliary proteins. One consequence of A‐channel structure is that several mechanisms could underlie the cell‐specific differences in pyloric IAs including differential gene expression, alternate splicing, and posttranslational modifications. Oocyte expression studies, single‐cell RT‐PCR, and immunocytochemistry suggest that differential α‐subunit gene expression is not a mechanism for creating pyloric IA heterogeneity, and that the same gene, shal, encodes the a‐subnuits for the entire family of somatic IAs in the pyloric network. Changes in the level of shal gene expression alter A‐channel density between cells, but cannot account for the differences in the biophysical properties of the six pyloric IAs. Preliminary data suggest that the shal gene also encodes the A‐channel α‐subunits for the coarse and fine neuropil but not for most axons. A second gene, shaker, encodes the A‐channel α‐subunits in the majority of axons and at the neuromuscular junction. The distinct properties of the two types of A‐channels are consistent with the different roles of IA at the different locations. Both the shaker and shal genes are alternately spliced, and investigations are under way to determine whether alternate splicing is a mechanism for generating pyloric IA heterogeneity.