Expression of inositol 1,4,5-trisphosphate receptors changes the Ca2+ signal of Xenopus oocytes

Abstract

The receptors for the second messenger inositol 1,4,5-trisphosphate [Ins(1,4,5)P3] form a family of closely related proteins that play an important role in regulating the free intracellular Ca2+ concentration. To test the hypothesis that changing the expression level of Ins(1,4,5)P3 receptors could alter the Ins(1,4,5)P3-mediated Ca2+ signal, we overexpressed Ins(1,4,5)P3 receptor type 1 (InsP3R-1) or type 3 (InsP3R-3) in Xenopus laevis oocytes. Expression of InsP3R-1 increased the velocity of the propagating waves of intracellular Ca2+ release but did not affect the Ins(1,4,5)P3-induced entry of extracellular Ca2+ across the plasma membrane. In contrast, expression of intracellular Ca2+ but markedly increased the magnitude and duration of Ca2+ influx. Immunolocalization studied revealed InsP3R-3 at the endoplasmic reticulum, with a relatively stronger signal at or near the plasma membrane. The results suggest that changing the expression level of an InsP3R can alter the Ins(1,4,5)P3-mediated Ca2+ signal and that InsP3R-1 and InsP3R-3 may have different biological functions.

Calcium influx factor is synthesized by yeast and mammalian cells depleted of organellar calcium stores

“…As with the much larger increases seen at the sections' peripheries, this apparent release from intracellular stores was not inhibited by the anti-IP 3 receptor antibody (data not shown). Injections of Ca 2ϩ (27), IP 3 (18,28), cyclic ADP ribose (29), and nicotinic acid adenine dinucleotide phosphate (NAADP) (29), even at high concentrations, did not result in [Ca 2ϩ ] i increases that resembled those observed with our preparations. In other experiments (data not shown), CIF was injected near the center of the oocyte.…”

“…Significant decreases in the fluorescence ratio became apparent only after 30 min. These data are similar to the persistence of Ca 2ϩ influxdependent Cl Ϫ currents seen by DeLisle et al in these cells after injection of a large amount of IP 3 (28). They may reflect the relative absence of catabolic processes in this cell that in mammalian cells lead to more rapid inactivation of the influx (7).…”

High Density Distribution of Endoplasmic Reticulum Proteins and Mitochondria at Specialized Ca2+ Release Sites in Oligodendrocyte Processes

“…Three subtypes of inositol 1,4,5-trisphosphate receptor (InsP 3 R) are now known (see Ref. 6 for review), which can have different modulatory properties and discrete functions even when expressed together in the same cell (7)(8)(9). Localization of calreticulin to InsP 3 R-containing membrane vesicles has been reported in some cell types using density gradient techniques (2,10).…”

Enhanced purinoceptor-mediated Ca2+ signalling in L-fibroblasts overexpressing type 1 inositol 1,4,5-trisphosphate receptors

“…a reduction in receptor-mediated InsP $ production) occurred following transfection [24]. However, more recently overexpression of the types 1 and 3 InsP $ Rs has been achieved in Xenopus oocytes [25] and Spodoptera frugiperda (Sf9) insect cells [10,26]. In the former study, InsP $ R1 overexpression in oocytes was shown to enhance cytosolic Ca# + wave propagation, presumably via an increased rate of intracellular Ca# + release, whereas type 3 InsP $ R overexpression enhanced Ca# + entry [25].…”