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First published online July 20, 2006
Journal of Experimental Biology 209, 2979-2989 (2006)
Published by The Company of Biologists 2006
doi: 10.1242/jeb.02314
Cloning and functional expression of voltage-gated ion channel subunits from cnidocytes of the Portuguese Man O'War Physalia physalis
1 Whitney Laboratory for Marine Bioscience, University of Florida, 9505
Ocean Shore Blvd, St Augustine, FL 32080, USA
2 Department of Physiology and Functional Genomics, University of Florida,
9505 Ocean Shore Blvd, St Augustine, FL 32080, USA
* Author for correspondence (e-mail: paa{at}whitney.ufl.edu)
Accepted 8 May 2006
Cnidocytes were dissociated from the tentacles of the Portuguese Man O'War
Physalia physalis using heat treatment, and purified using density
centrifugation. Visual observation confirmed that these cnidocytes contained a
nucleus, a cnidocyst and an apical stereocilium, confirming that the cells
were intact. A cnidocyte-specific amplified cDNA library was then prepared
using RNA isolated from the cnidocytes, and screened for voltage-gated ion
channel subunits using conventional molecular cloning techniques. A variety of
channel proteins were identified and full-length sequence obtained for two of
them, a Ca2+ channel ß subunit
(PpCaVß) and a Shaker-like K+
channel (PpKV1). The location of the transcripts was
confirmed by RT-PCR of total RNA isolated from individually selected and
rinsed cnidocytes. The functional properties of these two channel proteins
were characterized electrophysiologically using heterologous expression.
PpCaVß modulates currents carried by both cnidarian
and mammalian
1 subunits although the specifics of the
modulation differ. PpKV1 produces fast transient outward
currents that have properties typical of other Shaker channels. The
possible role of these channel proteins in the behavior of cnidocytes is
discussed.
Key words: Ca2+ beta subunit, potassium channel, Shaker, KV1, cnidaria, Physalia physalis