Stability study on renal type I mineralocorticoid receptor.
The purpose of this work is to review stability and activation properties of type I receptor, in order to explain the reasons for its extreme in vitro instability. We demonstrate that the treatment of rat kidney cytosol with H2O2 prevents aldosterone binding, DNA/steroid-receptor complex interactions, and prevents the receptor thermal inactivation. In contrast, exogenous sulfhydryl reducing reagents are necessary to insure maximum binding of mineralocorticoid receptor and DNA/steroid-receptor interaction. However, the presence of beta-mercaptoethanol in thermal induced incubations reverts the H2O2 protection. We also demonstrate that contaminations with free or sequestered iron are harmful for both, receptor binding capacity (in a reversible form) and for hormone-receptor/DNA binding properties (in a partially reversible form). We propose a sulfhydryl oxidative mechanism for type I mineralocorticoid receptor inactivation in which iron contaminants might accelerate this process by oxidative catalysis. We also demonstrate that when thiol groups are blocked by specific reagents such as N-ethyl-maleimide or dithionitrobenzoic acid, type I sites loose binding capacity, but the protein is protected from oxidation as well as inactivation.
Galigniana
M D
MD
Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina.
D000818:Animals; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007501:Iron / Q000378:metabolism; D007668:Kidney / Q000378:metabolism*; D008297:Male; D000451:Mineralocorticoid Receptor Antagonists; D011485:Protein Binding; D051381:Rats; D018161:Receptors, Mineralocorticoid / Q000378:metabolism*; D013438:Sulfhydryl Compounds / Q000378:metabolism
D000451:Mineralocorticoid Receptor Antagonists; D018161:Receptors, Mineralocorticoid; D013438:Sulfhydryl Compounds; D006861:Hydrogen Peroxide; D007501:Iron