AJP - Cell Physiology, Vol 249, Issue 3 215-C225, Copyright © 1985 by American Physiological Society
Aldosterone-induced proteins: characterization using lectin-affinity chromatography
B. Blazer-Yost and M. Cox
Aldosterone-stimulated Na+ transport in toad urinary bladder is associated
with the synthesis of a specific group of proteins whose induction appears
to be related to the natriferic effect of the hormone. These
aldosterone-induced proteins (AIPs) occur in two slightly different
molecular weight classes (around 70 kDa), each class being composed of
several proteins with discrete isoelectric points (range, 5.5-6.0). Because
glycosylation is a common cause of such electrophoretic polymorphism and
microheterogeneity, we examined whether these proteins are glycoproteins.
Tunicamycin (a specific inhibitor of N-linked glycosylation) inhibited
aldosterone-stimulated Na+ transport and AIP synthesis without affecting
overall protein synthesis. The vast majority of epithelial cell proteins
did not bind to the mannose-specific lectin, concanavalin A-sepharose. In
contrast, both classes of AIPs bound to concanavalin A-sepharose, but the
affinities of the higher and lower molecular weight proteins were markedly
different: the former were readily eluted with 0.2 M
alpha-methyl-D-mannoside alone, whereas the latter could only be eluted
with 0.4 M alpha-methyl-D-mannoside in combination with high concentrations
of NaCl (2.5-5.0 M). These studies indicate that 1) glycosylation is
important in the natriferic response to aldosterone, 2) the AIPs are
N-linked mannose-containing glycoproteins, and 3) the electrophoretic
polymorphism of the AIPs is due, at least in part, to differences in
glycosylation. Furthermore, concanavalin A-affinity chromatography provides
a simple means for the partial purification of these putative "effectors"
of the cellular action of aldosterone.
