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Rapamycin inhibits aldolase A expression during human lymphocyte activation
1Laboratory of Transplantation Immunology, Louis-Charles Simard Research Center, Notre-Dame Hospital, Montreal, Quebec, Canada.
Abstract:
Rapamycin (RAPA) strongly inhibits lymphocyte activation and proliferation, but does not affect most of the activation-related gene expression at the mRNA level. In order to understand the mechanism of action of RAPA and to gain further insights in lymphocyte signalling which is impaired by RAPA, we screened for RAPA-sensitive genes using differential hybridization. The expression of human aldolase A gene was found to be inducible during T and B cell activation, and the induction was repressed by RAPA at both the mRNA and enzymatic levels. The other two important immunosuppressants, cyclosporin A and FK506, also inhibited the mitogen-induced upregulation. However, none of these three drugs inhibited the constitutive expression. There was no fluctuation of aldolase A expression during the cell cycle, and RAPA failed to block the first cell cycle after synchronization in Jurkat cells. However, the second cycle was hampered by RAPA, and this was correlated with the inhibition of aldolase A expression during this later stage. Since aldolase A is a key enzyme in glycolysis and lymphocytes mainly depend on glycolysis for energy supply, the data from this study suggest that aldolase A might be one of the downstream targets of RAPA. The inhibition of the enzyme upregulation might deprive the cells of additional supply of energy, and prevent the cells from entering an optimal status for proliferation.
Insights
Rapamycin (RAPA) inhibits lymphocyte activation by repressing aldolase A, a key glycolytic enzyme. This mechanism may limit energy supply, hindering lymphocyte proliferation.
Area of Science:
- Immunology
- Molecular Biology
- Cell Biology
Background:
- Rapamycin (RAPA) inhibits lymphocyte activation and proliferation.
- Its precise molecular mechanisms, particularly gene expression effects, remain incompletely understood.
Purpose of the Study:
- To identify RAPA-sensitive genes involved in lymphocyte signaling.
- To elucidate the role of aldolase A in RAPA's immunosuppressive effects.
Main Methods:
- Differential hybridization screening for RAPA-sensitive genes.
- Analysis of human aldolase A gene expression during T and B cell activation.
- Assessment of RAPA, cyclosporin A, and FK506 effects on aldolase A expression.
- Cell cycle analysis of Jurkat cells treated with RAPA.
Main Results:
- Human aldolase A gene expression is induced during T and B cell activation.
- RAPA, cyclosporin A, and FK506 repressed this induction at mRNA and enzyme levels.
- RAPA inhibited aldolase A expression in the second cell cycle post-synchronization.
- Aldolase A induction was not observed during the cell cycle or in the first cycle.
Conclusions:
- Aldolase A is a potential downstream target of RAPA in lymphocytes.
- RAPA-mediated inhibition of aldolase A may impair glycolysis and energy supply.
- This energy depletion could contribute to RAPA's inhibition of lymphocyte proliferation.