The catabolite inactivation of Aspergillus nidulans isocitrate lyase occurs by specific autophagy of peroxisomes

In Aspergillus nidulans, activity of the glyoxylate cycle enzyme isocitrate lyase is finely regulated. Isocitrate lyase is induced by growth on C2 compounds and long-chain fatty acids and repressed by glucose. In addition, activity of isocitrate lyase is subject to a second mechanism of catabolite c...

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Bibliographic Details
Published in:Archives of microbiology 2000-07, Vol.174 (1-2), p.59-66
Main Authors: AMOR, C, DOMINGUEZ, A. I, RAMON DE LUCAS, J, LABORDA, F
Format: Article
Language:English
Subjects:
Aspergillus nidulans - drug effects
Aspergillus nidulans - enzymology
Aspergillus nidulans - ultrastructure
Autophagy - drug effects
Biological and medical sciences
Endopeptidases - metabolism
Fundamental and applied biological sciences. Psychology
Glucose - pharmacology
Growth, nutrition, metabolism, transports, enzymes. Molecular biology
Isocitrate Lyase - antagonists & inhibitors
Isocitrate Lyase - metabolism
Microbiology
Microscopy, Electron
Mycology
Peroxisomes - drug effects
Peroxisomes - ultrastructure
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Summary:In Aspergillus nidulans, activity of the glyoxylate cycle enzyme isocitrate lyase is finely regulated. Isocitrate lyase is induced by growth on C2 compounds and long-chain fatty acids and repressed by glucose. In addition, activity of isocitrate lyase is subject to a second mechanism of catabolite control, glucose-induced inactivation. Here, we demonstrate that the catabolite inactivation of A. nidulans isocitrate lyase, a process that takes place during glucose adaptation of cells grown under gluconeogenic conditions, occurs by proteolysis of the enzyme. Ultrastructural analyses were carried out in order to investigate the cellular processes that govern the catabolite inactivation of this peroxisomal enzyme. Addition of glucose to oleate-induced cells triggered the specific engulfment and sequestration of peroxisomes by the vacuoles. Sequestration of various peroxisomes by a single vacuole was a frequently observed phenomenon. Results obtained by immunoelectron microscopy using antibodies against A. nidulans isocitrate lyase showed that degradation of this peroxisomal enzyme occurred inside the vacuole. In addition, ultrastructural studies demonstrated that microautophagy was the autophagic pathway involved in degradation of redundant peroxisomes during glucose adaptation of oleate-induced cells of A. nidulans.
ISSN:0302-8933
1432-072X
DOI:10.1007/s002030000176