Ca2+/calmodulin-dependent protein kinase II activation and regulation of adrenal glomerulosa Ca2+ signaling.
We recently reported that elevations in the intracellular Ca2+ concentration ([Ca2+]i) enhance low-voltage-activated, 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+ signaling. AG cell extracts exhibited kinase activity toward a CaMKII-selective peptide substrate that was dependent on both Ca2+ [half-maximal concentration for Ca2+ activation (K0.5) = 1.5 microM] and calmodulin (K0.5 = 46 nM) and was sensitive to a calmodulin antagonist and a CaMKII peptide inhibitor. On cell treatment with elevated extracellular potassium (10-60 mM) or angiotensin II, Ca(2+)-independent CaMKII activity increased to 133-205% of basal activity. Ca(2+)-independent kinase activity in agonist-stimulated extracts was inhibited by the CaMKII inhibitor peptide, 1(-)[N,O-bis(1,5- isoquinolinesulfonyl)-N-methyl-L-tyrosyl]-4-phenylpiperazine (KN-62), a cell-permeable inhibitor of CaMKII, reduced the agonist-induced stimulation of Ca(2+)-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+ signaling through voltage-gated Ca2+ channels.
Fern
R J
RJ
Department of Pharmacology, University of Virginia Health Sciences Center, Charlottesville 22908, USA.
Hahm
M S
MS
Lu
H K
HK
Liu
L P
LP
Gorelick
F S
FS
Barrett
P Q
PQ
D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000502:physiology; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002417:Cattle; D004594:Electrophysiology; D004789:Enzyme Activation; D015640:Ion Channel Gating; D011188:Potassium / Q000494:pharmacology; D015398:Signal Transduction; D015384:Zona Glomerulosa / Q000166:cytology / Q000378:metabolism*
D015220:Calcium Channels; D000804:Angiotensin II; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D011188:Potassium; D002118:Calcium