INVESTIGADORES
GALIGNIANA Mario Daniel
artículos
Título:
Native rat kidney mineralocorticoid receptor is a phosphoprotein whose transformation to a DNA-binding form is induced by phosphatases
Autor/es:
GALIGNIANA MD
Revista:
BIOCHEMICAL JOURNAL
Editorial:
PORTLAND PRESS LTD
Referencias:
Año: 1998 vol. 333 p. 555 - 563
ISSN:
0264-6021
Resumen:
Addition of alkaline phosphatase to rat kidney cytosol diminishes the
ability of the mineralocorticoid receptor (MR) to bind aldosterone in a
time-, temperature- and concentration-dependent form. A variety of
phosphatase inhibitors, including levamisole, are effective in
preventing this inactivation. On the other hand, when the
steroid-receptor complex is incubated in the presence of alkaline
phosphatase, an increment in the rate of receptor transformation is
evidenced by a change in the sedimentation coefficient from 8.8 S to 5.1
S, as well as increased DNA-binding capacity. The effects of alkaline
phosphatase on activation and transformation can also be observed when
the MR is incubated at 20 degreesC in the cytosolic medium, indicating
that the catalytic action of an endogenous phosphatase may be involved
in the transformation process. The ability of phosphatase inhibitors
such as levamisole for suppressing both alkaline phosphatase- and
endogenous phosphatase-directed transformation does not correspond well
between them. Evidence is presented to affirm that the endogenous
phosphatase activity is not due to an alkaline phosphatase-type, but it
may be due to a protein serine/threonine phosphatase, as evidenced by
the inhibitory effects of okadaic acid. The experimental results also
show direct evidence that the MR undergoes phosphorylation in a
physiological milieu.