Related Experiment Videos
Functional properties of the type-3 InsP3 receptor in 16HBE14o- bronchial mucosal cells
L Missiaen1, J B Parys, I Sienaert
1Laboratorium voor Fysiologie, K. U. Leuven Campus Gasthuisberg, Herestraat 49, B-3000 Leuven, Belgium. Ludwig.Missiaen@med.kuleuven.ac.be
Abstract:
The type-3 inositol 1,4,5-trisphosphate (InsP3) receptor is the major isoform expressed in 16HBE14o- cells from bronchial mucosa, representing 93% at the mRNA level as determined by ratio reverse transcription-polymerase chain reaction and about 81% at the protein level as determined with isoform-specific antibodies (Sienaert, I., Huyghe, S., Parys, J. B., Malfait, M., Kunzelmann, K., De Smedt, H., Verleden, G. M., and Missiaen, L., Pflügers Arch. Eur. Y. Physiol., in press). The present 45Ca2+ efflux experiments indicate that these InsP3 receptors were 3 times less sensitive to InsP3 and 11 times less sensitive to ATP than those in A7r5 cells, where the type-1 InsP3 receptor is the main isoform. ATP did not increase the cooperativity of the InsP3-induced Ca2+ release in 16HBE14o- cells, in contrast to its effect in A7r5 cells. The sulfhydryl reagent thimerosal also did not stimulate InsP3-induced Ca2+ release in 16HBE14o- cells, again in contrast to its effect in A7r5 cells. Adenophostin A was more potent than InsP3 in stimulating the release in both cell types. The biphasic activation of the InsP3 receptor by cytosolic Ca2+ occurred in both cell types. We conclude that Ca2+ release mediated by the type-3 InsP3 receptor mainly differs from that mediated by the type-1 InsP3 receptor by its lack of stimulation by sulfhydryl oxidation and its lower ATP and InsP3 sensitivity. The predominant expression of the type-3 InsP3 receptor in the bronchial mucosa may be part of a mechanism coping with oxidative stress in that tissue.
Insights
The type-3 inositol 1,4,5-trisphosphate (InsP3) receptor in bronchial cells is less sensitive to InsP3 and ATP than type-1 receptors. This difference may help manage oxidative stress in lung tissue.
Area of Science:
- Cellular Biology
- Physiology
Background:
- The inositol 1,4,5-trisphosphate (InsP3) receptor is crucial for intracellular calcium (Ca2+) signaling.
- Different InsP3 receptor isoforms exhibit distinct properties and expression patterns.
- The bronchial mucosa primarily expresses the type-3 InsP3 receptor isoform.
Purpose of the Study:
- To characterize the functional properties of the type-3 InsP3 receptor in bronchial cells.
- To compare the sensitivity and regulation of type-3 InsP3 receptors with type-1 InsP3 receptors.
- To elucidate the role of type-3 InsP3 receptors in the context of bronchial mucosa physiology.
Main Methods:
- Quantitative analysis of InsP3 receptor mRNA and protein expression in 16HBE14o- cells.
- 45Ca2+ efflux experiments to measure InsP3-induced Ca2+ release.
- Assessment of InsP3 receptor sensitivity to InsP3, ATP, and thimerosal.
- Comparison of InsP3 receptor function between 16HBE14o- cells (type-3) and A7r5 cells (type-1).
Main Results:
- Type-3 InsP3 receptors in 16HBE14o- cells showed lower sensitivity to InsP3 (3-fold) and ATP (11-fold) compared to type-1 receptors in A7r5 cells.
- ATP did not enhance cooperativity of Ca2+ release for type-3 receptors, unlike for type-1.
- Thimerosal did not stimulate Ca2+ release via type-3 receptors, contrasting with its effect on type-1 receptors.
- Adenophostin A was a more potent stimulator than InsP3 for both cell types.
- Biphasic activation of InsP3 receptors by cytosolic Ca2+ was observed in both cell types.
Conclusions:
- Type-3 InsP3 receptors differ from type-1 by reduced sensitivity to InsP3 and ATP, and lack of stimulation by sulfhydryl oxidation.
- The predominant expression of type-3 InsP3 receptors in bronchial mucosa may be an adaptation to cope with oxidative stress.
- These findings provide insights into the specific roles of InsP3 receptor isoforms in different tissues.