Ca2+/calmodulin-dependent protein kinase ii activation and
regulation of adrenal glomerulosa ca2+ signalling.
Fern, Robert J., Michael S. Hahm, Hong-Kai Lu, Li Ping Liu, Fred S.
Gorelick, and Paula Q. Barrett.
Department of Pharmacology, University of Virginia Health Sciences
Center, Charlottesville, Virginia 22908, Department of Cell Biology,
Yale University School of Medicine, New Haven, Connecticut 06510
APStracts 2:0110F, 1995.
We recently reported that elevations in the intracellular Ca2+
concentration ([Ca2+]i) enhance low voltage-gated, T-type, Ca2+
channel activity via Ca2+/calmodulin-dependent protein kinase II
(CaMKII). Here, we document CaMKII activity in bovine adrenal
glomerulosa (AG) cells and assess the importance of CaMKII in
depolarization-induced Ca2+ signalling. AG cell extracts exhibited
kinase activity toward a CaMKII-selective peptide substrate that was
dependent upon both Ca2+ (K0.5 = 1.5 [mu]M) and calmodulin (K0.5 = 46
nM) and was sensitive to a calmodulin antagonist and a CaMKII peptide
inhibitor. Upon cell treatment with elevated extracellular potassium
(K+o, 10-60 mM) or angiotensin II, Ca2+-independent CaMKII activity
increased to 133-205% of basal activity. Ca2+-independent kinase
activity in agonist-stimulated extracts was inhibited by the CaMKII
inhibitor peptide. KN-62, a cell-permeable inhibitor of CaMKII,
reduced the agonist-induced stimulation of Ca2+-independent CaMKII
activity. KN-62 also diminished depolarization-induced increases in
[Ca2+]i without affecting the membrane potential. These observations
suggest that CaMKII is activated in situ by aldosterone secretagogues
and augments Ca2+ signalling through voltage-gated Ca2+ channels.
Received 30 January 1995; accepted in final form 12 June 1995.
APS Manuscript Number F26-5.
Article publication pending Am. J. Physiol. (Renal Fluid Electrolyte
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 11 July 1995.