scholarly journals Muscarinic activation of Ca2+/calmodulin-dependent protein kinase II in pancreatic islets. Temporal dissociation of kinase activation and insulin secretion

1996 ◽  
Vol 317 (1) ◽  
pp. 167-172 ◽  
Author(s):  
Eric L. BABB ◽  
Jim TARPLEY ◽  
Michael LANDT ◽  
Richard A. EASOM
Keyword(s):  
Insulin Secretion ◽  
Protein Kinase ◽  
Pancreatic Islets ◽  
Cam Kinase Ii ◽  
Muscarinic Agonist ◽  
Cam Kinase ◽  
Dependent Protein Kinase ◽  
Kinase Activation ◽  
Protein Kinase Ii ◽  
Dependent Protein

We have demonstrated previously that glucose activates the multifunctional Ca2+/calmodulin-dependent protein kinase II (CaM kinase II) in isolated rat pancreatic islets in a manner consistent with a role of this enzyme in the regulation of insulin secretion [Wenham, Landt and Easom (1994) J. Biol. Chem. 269, 4947–4952]. In the current study, the muscarinic agonist, carbachol, has been shown to induce the conversion of CaM kinase II into a Ca2+-independent, autonomous form indicative of its activation. Maximal activation (2-fold) was achieved by 15 s, followed by a rapid return to basal levels by 1 min. This response was primarily the result of the mobilization of Ca2+ from intracellular stores since it was not affected by a concentration (20 μM) of verapamil that completely prevented the activation of CaM kinase II by glucose. Surprisingly, carbachol added prior to, or simultaneously with, glucose attenuated nutrient activation of CaM kinase II. This effect was mimicked by cholecystokinin-8 (CCK-8) and thapsigargin, suggesting its mediation by phospholipase C and the mobilization of intracellular Ca2+. In contrast, carbachol, CCK-8 and thapsigargin markedly potentiated glucose (12 mM)-induced insulin secretion. These results suggest that CaM kinase II activation can be temporally dissociated from insulin secretion but do not exclude the potential dependence of insulin exocytosis on CaM kinase II-mediated protein phosphorylation.

scholarly journals Correlation of the Activation of Ca2+/Calmodulin-Dependent Protein Kinase II with the Initiation of Insulin Secretion from Perifused Pancreatic Islets*

Endocrinology ◽  
1997 ◽  
Vol 138 (6) ◽  
pp. 2359-2364 ◽  
Author(s):  
Richard A. Easom ◽  
Natalie R. Filler ◽  
Emma M. Ings ◽  
Jim Tarpley ◽  
Michael Landt
Keyword(s):  
Insulin Secretion ◽  
Protein Kinase ◽  
Second Phase ◽  
Cam Kinase Ii ◽  
Cam Kinase ◽  
Dependent Protein Kinase ◽  
Kinase Activation ◽  
Protein Kinase Ii ◽  
Dependent Protein ◽  
Perifused Islets

Abstract An experimental procedure has been designed to permit the simultaneous assessment of the activation status of the multifunctional Ca2+/calmodulin-dependent protein kinase II (CaM kinase II) with insulin secretion in perifused islets. By this procedure, the activation of CaM kinase II by glucose correlated closely with the initial and sustained phases of insulin secretion within a 30-min test period. By contrast, islets (160–200/tube) in static incubations neither supported second-phase insulin secretion nor CaM kinase II activation beyond 10–15 min. This was not the result of the accumulation of insulin, because the introduction of insulin (40–160 ng/ml) into the perifusion medium failed to mimic the suppression of glucose-induced insulin secretion or CaM kinase II activation. A similar addition of SRIF (0.01–1 μm) or epinephrine (1μ m) profoundly suppressed insulin secretion although failing to significantly influence CaM kinase II activation. Finally, on withdrawal of glucose from perifused islets, insulin secretion rapidly returned to basal rates, but CaM kinase II deactivation was significantly delayed. The correlation of kinase activation with the initiation of insulin secretion suggests that CaM kinase II may be important in the regulation of glucose-induced insulin secretion. The observed dissociation of these parameters in the presence of inhibitory hormones or after the withdrawal of a glucose stimulus, however, suggests that the kinase is not directly involved in the final steps of insulin exocytosis.

scholarly journals Co-distribution of calmodulin-dependent protein kinase II and inositol trisphosphate receptors in an apical domain of gastrointestinal mucosal cells.

1996 ◽  
Vol 44 (11) ◽  
pp. 1243-1250 ◽  
Author(s):  
L M Matovcik ◽  
A R Maranto ◽  
C J Soroka ◽  
F S Gorelick ◽  
J Smith ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Pancreatic Acinar Cells ◽  
Apical Region ◽  
Cam Kinase Ii ◽  
Cam Kinase ◽  
Dependent Protein Kinase ◽  
Protein Kinase Ii ◽  
Dependent Protein ◽  
Type 3 ◽  
Insp3 Receptor

The Type 3 inositol 1,4,5-trisphosphate (InsP3) receptor is expressed at high levels in gastrointestinal tissues. This receptor has 16 potential phosphorylation sites for calcium/calmodulin-dependent protein kinase II (CaM kinase II). To determine if the Type 3 InsP3 receptor is likely to be a physiologic substrate for CaM kinase II, localizations of the Type 3 InsP3 receptor and CaM kinase II were compared in tissues of the gastrointestinal tract. Cellular and subcellular localizations were determined by immunofluorescence microscopy in rat intestine, pancreas, and stomach, and in isolated rabbit gastric glands. Both proteins were found in the apical region of intestinal enterocytes, pancreatic acinar cells, and gastric parietal, chief, and surface mucous cells. CaM kinase II was found throughout the entire intracellular canalicular F-actin domain of parietal cells, whereas the type 3 InsP3 receptor was restricted to the neck region. Thus, in several gastrointestinal tissues the Type 3 InsP3 receptor is specifically localized to a portion of the apical cytoskeletal domain in which resides the calcium-responsive effector CaM kinase II.

scholarly journals Global Forebrain Ischemia Results in Decreased Immunoreactivity of Calcium/Calmodulin-Dependent Protein Kinase II

1992 ◽  
Vol 12 (5) ◽  
pp. 784-793 ◽  
Author(s):  
Severn B. Churn ◽  
Amy Yaghmai ◽  
John Povlishock ◽  
Azhar Rafiq ◽  
Robert J. DeLorenzo
Keyword(s):  
Monoclonal Antibody ◽  
Protein Kinase ◽  
Neuronal Cell ◽  
Cam Kinase Ii ◽  
Forebrain Ischemia ◽  
Cam Kinase ◽  
Dependent Protein Kinase ◽  
Calcium Calmodulin Dependent ◽  
Protein Kinase Ii ◽  
Dependent Protein

Previous studies utilizing crude brain homogenates have shown that forebrain ischemia results in inhibition of calcium/calmodulin-dependent protein kinase II (CaM kinase II) activity without large-scale proteolysis of the enzyme. In this report, a monoclonal antibody (1C3-3D6) directed against the β- (60-kDa) subunit of CaM kinase II that does not recognize ischemically altered enzyme was utilized to further investigate the ischemia-induced inhibition of CaM kinase II. Immunohistochemical investigations showed that the ischemia-induced decreased immunoreactivity of CaM kinase II occurred immediately following ischemic insult in ischemia-sensitive cells such as pyramidal cells of the hippocampus. No decrease in CaM kinase II immunoreactivity was observed in ischemia-resistant cells such as granule cells of the dentate gyrus. The decreased immunoreactivity was observed for CaM kinase II balanced for protein staining and calmodulin binding in vitro. In addition, autophosphorylation of CaM kinase II in the presence of low (7 μ M) or high (500 μ M) ATP did not alter immunoreactivity of the enzyme with 1C3-3D6. The data demonstrate the production of a monoclonal antibody that recognizes the β-subunit of CaM kinase II in a highly specific manner, but does not recognize ischemic enzyme. Together with previous studies, the data support the hypothesis that rapid, ischemia-induced inhibition of CaM kinase II activity may be involved in the cascade of events that lead to selective neuronal cell loss in stroke.

scholarly journals Dephosphorylation and deactivation of Ca2+/calmodulin-dependent protein kinase II in βTC3-cells is mediated by Mg2+- and okadaic-acid-sensitive protein phosphatases

1998 ◽  
Vol 329 (2) ◽  
pp. 283-288 ◽  
Author(s):  
A. Richard EASOM ◽  
L. Jim TARPLEY ◽  
R. Natalie FILLER ◽  
Harshika BHATT
Keyword(s):  
Protein Kinase ◽  
Okadaic Acid ◽  
Protein Phosphatases ◽  
Cam Kinase Ii ◽  
Calyculin A ◽  
Cam Kinase ◽  
Dependent Protein Kinase ◽  
Protein Kinase Ii ◽  
Dependent Protein ◽  
Combined Action

The α-toxin-permeabilized βTC3 cell has been utilized as an experimental model for the identification of protein phosphatases responsible for the dephosphorylation and deactivation of Ca2+/calmodulin-dependent protein kinase II (CaM kinase II) in situ. In this model, the elevation of Ca2+ from 0.05 to 10 μM induced the near-total conversion of CaM kinase II into a Ca2+/calmodulin-independent (autonomous) form characteristic of autophosphorylated, activated enzyme. On the removal of Ca2+, the activation state of CaM Kinase II rapidly returned to prestimulated levels. This reversal was slowed, but not prevented, by the inhibitors of protein phosphatase-1 (PP-1) and PP-2A, okadaic acid and calyculin A, and by the selective chelation of Mg2+ by the addition of EDTA. Near-complete prevention of enzyme deactivation, however, was observed in the combined presence of both okadaic acid and EDTA. Under these conditions, CaM kinase II phosphatase was more sensitive to calyculin A relative to okadaic acid, characteristic of the involvement of PP-1. CaM kinase II deactivation was not affected by FK-506, eliminating the involvement of PP-2B in this process. These data suggest that CaM kinase II dephosphorylation and deactivation in the pancreatic β-cell is mediated by the combined action of an okadaic-acid-sensitive phosphatase and a Mg2+-dependent phosphatase, such as PP-2C.

scholarly journals Regulation of endothelial cell barrier function by calcium/calmodulin-dependent protein kinase II

2001 ◽  
Vol 280 (5) ◽  
pp. L983-L990 ◽  
Author(s):  
Talaibek Borbiev ◽  
Alexander D. Verin ◽  
Shu Shi ◽  
Feng Liu ◽  
Joe G. N. Garcia
Keyword(s):  
Endothelial Cell ◽  
Protein Kinase ◽  
Phosphorylation Site ◽  
Cam Kinase Ii ◽  
Dependent Manner ◽  
Cam Kinase ◽  
Barrier Dysfunction ◽  
Dependent Protein Kinase ◽  
Protein Kinase Ii ◽  
Dependent Protein

Thrombin-induced endothelial cell barrier dysfunction is tightly linked to Ca2+-dependent cytoskeletal protein reorganization. In this study, we found that thrombin increased Ca2+/calmodulin-dependent protein kinase II (CaM kinase II) activities in a Ca2+- and time-dependent manner in bovine pulmonary endothelium with maximal activity at 5 min. Pretreatment with KN-93, a specific CaM kinase II inhibitor, attenuated both thrombin-induced increases in monolayer permeability to albumin and decreases in transendothelial electrical resistance (TER). We next explored potential thrombin-induced CaM kinase II cytoskeletal targets and found that thrombin causes translocation and significant phosphorylation of nonmuscle filamin (ABP-280), which was attenuated by KN-93, whereas thrombin-induced myosin light chain phosphorylation was unaffected. Furthermore, a cell-permeable N-myristoylated synthetic filamin peptide (containing the COOH-terminal CaM kinase II phosphorylation site) attenuated both thrombin-induced filamin phosphorylation and decreases in TER. Together, these studies indicate that CaM kinase II activation and filamin phosphorylation may participate in thrombin-induced cytoskeletal reorganization and endothelial barrier dysfunction.

scholarly journals New isoforms of Ca2+/calmodulin-dependent protein kinase II in smooth muscle

1994 ◽  
Vol 299 (2) ◽  
pp. 489-495 ◽  
Author(s):  
Z L Zhou ◽  
M Ikebe
Keyword(s):  
Smooth Muscle ◽  
Alternative Splicing ◽  
Protein Kinase ◽  
Variable Region ◽  
Rat Aorta ◽  
Cam Kinase Ii ◽  
Cam Kinase ◽  
Dependent Protein Kinase ◽  
Protein Kinase Ii ◽  
Dependent Protein

Four novel isoforms of Ca2+/calmodulin-dependent protein kinase II (CaM kinase II) were found in rat aorta smooth muscle. Two of them were related to gamma-isoform of brain CaM kinase II (gamma-a). Differences in the primary structure of these isoforms were located in the variable region. One of them (gamma-b) contained 23 unique amino acid residues, whereas the other (gamma-c) did not contain this sequence. Both isoforms lacked the two segments (Val-316 to Gln-337 and Lys-353 to Leu-362) present in gamma-a. The DNA sequence of these gamma-isoforms except the variable region was exactly the same, suggesting that they are produced by alternative splicing. Another two isoforms were related to the delta-isoform of brain CaM kinase II (delta-a). delta-b contained a unique 11-residue sequence in the variable region whereas delta-c did not. As found for gamma-isoforms, the sequence analysis suggested that the three delta-isoforms are also produced by alternative splicing. Analysis of RNA by reverse transcription PCR confirmed the existence of specific messages for gamma-b, delta-a and delta-b. The variety of isoforms of CaM kinase II suggest that each isoform may play a specialized role in cell regulation.

scholarly journals Structural features of Ca2+/calmodulin-dependent protein kinase II revealed by electron microscopy.

1991 ◽  
Vol 115 (4) ◽  
pp. 1049-1060 ◽  
Author(s):  
T Kanaseki ◽  
Y Ikeuchi ◽  
H Sugiura ◽  
T Yamauchi
Keyword(s):  
Protein Kinase ◽  
Molecular Conformation ◽  
Structural Features ◽  
Cam Kinase Ii ◽  
Cam Kinase ◽  
Dependent Protein Kinase ◽  
Quick Freezing ◽  
Protein Kinase Ii ◽  
Dependent Protein ◽  
Central Particle

The molecular conformation of Ca2+/calmodulin-dependent protein kinase II (CaM kinase II) from the rat forebrain and cerebellum was studied by means of EM using a quick-freezing technique. Each molecule appeared to be composed of two kinds of particles, with one larger central particle and smaller peripheral particles and had shapes resembling that of a flower with 8 or 10 "petals". A favorable shadowing revealed that each peripheral particle had a thin link to the central particle. We predicted that the 8-petal molecules and 10-petal molecules were octamers and decamers of CaM kinase II subunits, respectively, each assembled with the association domains of subunits gathered in the center, and the catalytic domains in the peripheral particles. Binding of antibodies to the enzyme molecules suggested that molecules with 8 and 10 peripheral particles were homopolymers composed only of beta subunit and of alpha subunit, respectively, specifying that CaM kinase II consists of homopolymer of either alpha or beta subunits.

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