Sustained elevation of intracellular Ca2+ by cell surface receptors is often dependent on influx of Ca2+ across the plasma membrane through routes not involving voltage-gated Ca2+ channels. We demonstrate that intracellular release of inositol 1,4,5-trisphosphate (InsP3), either from stimulation of transfected human muscarinic receptors or from photolytic release of caged InsP3, activates whole cell Ca2+ current in the Jurkat T cell line. Whole cell voltage clamp recordings indicate that the current is carried by a Ca2+-selective channel that resembles T-type voltage-gated Ca2+ channels in relative conductance of different cation species. Elevation of internal Ca2+ inactivates the channel, whereas internal perfusion with inositol 1,3,4,5-tetrakisphosphate (InsP4) does not affect it. Photolytic release of caged 1-(α-glycerophosphoryl)-inositol 4,5- bisphosphate, an analog of InsP3 which activates InsP3 receptors but is not readily metabolized to InsP4, also activates the current. We conclude that generation of InsP3 is sufficient to activate Ca2+-selective channels in the plasma membrane of T cells. InsP3 may have its effect indirectly through depletion of Ca2+ stores, or directly with a plasma membrane-associated InsP3 receptor.
|Original language||English (US)|
|Number of pages||8|
|Journal||Journal of Biological Chemistry|
|State||Published - 1993|
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology