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Dexamethasone up-regulates mannose receptor activity by increasing mRNA levels
H B Cowan1, S Vick, J T Conary
1Department of Medicine, Vanderbilt University, Nashville, Tennessee 37203.
Archives of Biochemistry and Biophysics
|July 1, 1992
Summary
Dexamethasone significantly increases macrophage mannose receptor activity by up-regulating messenger RNA (mRNA) levels. This leads to increased synthesis of new mannose receptor protein in rat bone marrow macrophages.
Area of Science:
- Immunology
- Cell Biology
- Molecular Biology
Background:
- The macrophage mannose receptor (MMR) is crucial for immune responses.
- Previous research indicated dexamethasone enhances MMR activity in macrophages.
Purpose of the Study:
- To investigate the molecular mechanisms behind dexamethasone-induced MMR up-regulation.
- To determine if dexamethasone affects MMR protein synthesis or mRNA expression.
Main Methods:
- Rat bone marrow macrophages were treated with varying concentrations and durations of dexamethasone.
- Ligand uptake assays measured MMR activity.
- Immunoprecipitation quantified total receptor protein.
- Oligonucleotide probes assessed mannose receptor mRNA levels.
Main Results:
- Dexamethasone increased MMR ligand uptake 2.5-fold in a dose- and time-dependent manner.
- Cell surface binding sites and total cellular binding activity increased to 250% of control.
- Total receptor protein levels rose by 2.5-fold.
- Mannose receptor mRNA levels significantly increased after 12-24 hours of dexamethasone treatment.
Conclusions:
- Dexamethasone treatment induces the synthesis of new mannose receptor protein.
- This synthesis is mediated by an increase in mannose receptor mRNA levels.
- Dexamethasone enhances MMR expression through transcriptional regulation.