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J. Cell Biol.,
Volume 140, Number 1, January 12, 1998 143-152
Howard Hughes Medical Institute, Departments of Internal Medicine and Physiology and Biophysics, University of Iowa
College of Medicine, Iowa City, Iowa 52242
Drosophila melanogaster has proven to be a
good model for understanding the physiology of ion
channels. We identified two novel Drosophila DEG/
ENaC proteins, Pickpocket (PPK) and Ripped Pocket
(RPK). Both appear to be ion channel subunits. Expression of RPK generated multimeric Na+ channels
that were dominantly activated by a mutation associated with neurodegeneration. Amiloride and gadolinium, which block mechanosensation in vivo, inhibited
RPK channels. Although PPK did not form channels
on its own, it associated with and reduced the current
generated by a related human brain Na+ channel. RPK
transcripts were abundant in early stage embryos, suggesting a role in development. In contrast, PPK was
found in sensory dendrites of a subset of peripheral
neurons in late stage embryos and early larvae. In insects, such multiple dendritic neurons play key roles in
touch sensation and proprioception and their morphology resembles human mechanosensory free nerve endings. These results suggest that PPK may be a channel
subunit involved in mechanosensation.
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