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Calcium uptake and gp80 messenger RNA destabilization follows cAMP receptor down regulation in Dictyostelium
Abstract:
The mechanism by which high concentrations of cAMP selectively destabilize the gp80 mRNA in Dictyostelium discoideum was investigated. This treatment which leads to down-regulation of the cAMP receptor was also found to cause an increase in calcium uptake. Given this observation, we sought a role for calcium as a second messenger in the degradation of the gp80 mRNA. Changes in the mRNA levels were examined after treating cells with compounds known to alter their intracellular Ca2+ concentrations. This included the use of A23187, Ca2+, 8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate HC1 (TMB-8), LiCl and 8-p-chlorophenylthioadenosine 3',5'-cyclic monophosphate (ClPhS-Ado-3':5'-P). The sum of the data suggest that it is the cAMP-induced influx of Ca2+ across the plasma membrane, as apposed to a cAMP-mediated release of Ca2+ from intracellular stores, that initiates gp80 mRNA degradation. Treatment of cells with Concanavalin A (ConA) to induce cAMP receptor down-regulation, also causes a reduction in gp80 mRNA levels and an increase in calcium uptake.
Insights
High cyclic adenosine monophosphate (cAMP) concentrations destabilize gp80 mRNA in Dictyostelium discoideum. This process is initiated by calcium influx, not intracellular calcium release, suggesting calcium acts as a second messenger.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Cyclic adenosine monophosphate (cAMP) regulates gene expression in Dictyostelium discoideum.
- High cAMP concentrations lead to down-regulation of the cAMP receptor and affect gp80 mRNA levels.
- An observed increase in calcium uptake during cAMP treatment prompted investigation into calcium's role.
Purpose of the Study:
- To elucidate the mechanism by which high cAMP concentrations destabilize gp80 mRNA.
- To determine if calcium acts as a second messenger in the degradation of gp80 mRNA.
- To differentiate between extracellular calcium influx and intracellular calcium release in mediating mRNA degradation.
Main Methods:
- Investigated changes in gp80 mRNA levels in Dictyostelium discoideum cells.
- Treated cells with various compounds to alter intracellular calcium concentrations, including A23187, Ca2+, TMB-8, LiCl, and ClPhS-Ado-3':5'-P.
- Utilized Concanavalin A (ConA) to induce cAMP receptor down-regulation and observed its effect on gp80 mRNA and calcium uptake.
Main Results:
- High cAMP concentrations selectively destabilize gp80 mRNA.
- The degradation of gp80 mRNA is triggered by the influx of calcium across the plasma membrane, not by the release of calcium from intracellular stores.
- Concanavalin A treatment, which down-regulates cAMP receptors, also reduces gp80 mRNA levels and increases calcium uptake.
Conclusions:
- Calcium influx, stimulated by cAMP, is the primary initiator of gp80 mRNA degradation in Dictyostelium discoideum.
- This finding highlights the critical role of extracellular calcium signaling in regulating specific mRNA stability.
- The study provides a mechanistic link between cAMP signaling, calcium homeostasis, and gene expression control.