Inositol-1,4,5-trisphosphate activates the drosophila cation
channel trpl in recombinant baculovirus-infected sf9 insect
cells.
Dong, Yanjie, Diana L. Kunze, Luis Vaca, and William P. Schilling.
Rammelkamp Center for Research, Case Western Reserve University,
MetroHealth Campus, Cleveland OH 44109-1998
APStracts 2:0273C, 1995.
The trpl gene product is thought to form a non-selective cation
channel important for signal transduction in Drosophila photoreceptor
cells. This channel may be the insect homologue of mammalian channels
involved in Ca2+ signal transduction. To determine the mechanism of
receptor-mediated activation of Trpl, whole cell membrane currents
were examined in Sf9 insect cells following infection with
recombinant baculovirus. Stimulation by bradykinin increased whole
-cell Trpl currents 3- to 5-fold. Similar activation of Trpl was
observed by inclusion of inositol-1,4,5-trisphosphate (Ins(1,4,5)P3)
in the pipette solution during whole cell recordings. These currents
were 1) not seen in non-infected cells or in cells expressing only
the B2 receptor, 2) mimicked by Ins(2,4,5)P3, and 3-fluoro
-Ins(1,4,5)P3, 3) not seen with Ins(1,4)P2 or Ins(1,3,4,5)P4, and 4)
blocked by heparin, but not by de-N-sulfated heparin. In contrast,
Trpl currents were unaffected by thapsigargin. These results
demonstrate that the Trpl cation channel is activated by Ins(1,4,5)P3
in a heparin-sensitive fashion. Regulation of channel activity by
Ins(1,4,5)P3 may occur by a number of mechanisms including direct
binding of Ins(1,4,5)P3 to the Trpl channel or direct physical
interaction between the Ins(1,4,5)P3 receptor/Ca2+-release channel of
the endoplasmic reticulum and the Trpl protein.
Received 10 May 1995; accepted in final form 28 June 1995.
APS Manuscript Number C249-5.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 30 July 1995.