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Manganese attenuates secretagogue-mediated phospholipid hydrolysis in AR42J cells
Abstract:
The effects of cholecystokinin octapeptide (CCK8), bombesin and manganese (Mn2+) on phosphatidylinositol-4,5-bisphosphate (PIP2) hydrolysis were studied in AR42J cells. One-half maximal stimulation of inositol monophosphate (InsP1) accumulation occurred at either 5 nM CCK8 or 5 nM bombesin, and maximal stimulation occurred at 30 nM for each agonist. Mn2+ did not alter basal PIP2 hydrolysis. However, addition of Mn2+ 5 min prior to stimulation with either CCK8 or bombesin for 60 min significantly attenuated [3H]InsP1 accumulation. Following brief periods of incubation with CCK8 (15 sec) Mn2+ significantly reduced inositol tris- and tetrakisphosphate accumulation. These data suggest that Mn2+ may participate in the regulation of CCK8- and bombesin-mediated generation of phosphoinositides.
Insights
Manganese (Mn2+) affects how cells respond to cholecystokinin octapeptide (CCK8) and bombesin. This study shows Mn2+ can regulate phosphoinositide generation in response to these signaling peptides.
Area of Science:
- Cellular signaling pathways
- Biochemistry of signal transduction
- Gastrointestinal peptide receptor interactions
Background:
- Phosphatidylinositol-4,5-bisphosphate (PIP2) hydrolysis is a key step in cellular signal transduction.
- Cholecystokinin octapeptide (CCK8) and bombesin are peptides that activate specific cellular receptors.
- The role of divalent cations like manganese (Mn2+) in modulating these signaling pathways is not fully understood.
Purpose of the Study:
- To investigate the effects of CCK8, bombesin, and Mn2+ on PIP2 hydrolysis in AR42J cells.
- To determine if Mn2+ influences the accumulation of inositol phosphates (InsP1, InsP3, InsP4) stimulated by CCK8 and bombesin.
- To elucidate the potential regulatory role of Mn2+ in CCK8- and bombesin-mediated phosphoinositide generation.
Main Methods:
- AR42J cells were treated with varying concentrations of CCK8 and bombesin.
- Measurement of inositol monophosphate (InsP1) accumulation as an indicator of PIP2 hydrolysis.
- Assessment of the impact of Mn2+ on basal and agonist-stimulated InsP1, inositol trisphosphate, and inositol tetrakisphosphate accumulation.
Main Results:
- CCK8 and bombesin stimulated InsP1 accumulation in a dose-dependent manner, with half-maximal effects at 5 nM and maximal effects at 30 nM.
- Mn2+ did not affect basal PIP2 hydrolysis but significantly attenuated agonist-induced InsP1 accumulation.
- Pre-incubation with Mn2+ reduced the accumulation of inositol tris- and tetrakisphosphates following brief CCK8 stimulation.
Conclusions:
- Mn2+ plays a regulatory role in CCK8- and bombesin-mediated phosphoinositide generation.
- The findings suggest a modulatory effect of Mn2+ on the signaling cascade initiated by CCK8 and bombesin.
- Further research is warranted to understand the precise mechanism by which Mn2+ interacts with these signaling pathways.