scholarly journals A comparative study of the activation of protein kinase C α by different diacylglycerol isomers

1999 ◽  
Vol 337 (3) ◽  
pp. 387-395 ◽  
Author(s):  
Pilar SÁNCHEZ-PIÑERA ◽  
Vicente MICOL ◽  
Senena CORBALÁN-GARCÍA ◽  
Juan C. G. ÓMEZ-FERNÁNDEZ
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Mixed Micelles ◽  
Fatty Acyl ◽  
Molar Ratio ◽  
Binding Studies ◽  
Scanning Calorimetry ◽  
Kinase C ◽  
Triton X ◽  
Activation Capacity

The lipid activation of protein kinase C α (PKC α) has been studied by comparing the activation capacity of different 1,2-diacylglycerols and 1,3-diacylglycerols incorporated into mixed micelles or vesicles. Unsaturated 1,2-diacylglycerols were, in general, more potent activators than saturated ones when 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoserine (POPS)/Triton X-100 mixed micelles and pure POPS vesicles were used. In contrast, these differences were not observed when 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC)/POPS (4:1, molar ratio) vesicles were used. Diacylglycerols bearing short fatty acyl chains showed a very high activation capacity, however, the capacity was less in mixed micelles. Furthermore, 1,2-diacylglycerols had a considerably higher activating capacity than 1,3-diacylglycerols in POPS/Triton X-100 mixed micelles and in POPC/POPS vesicles. However, the differences between the two types of diacylglycerols were smaller when pure POPS vesicles were used. Differential scanning calorimetry (DSC) showed that POPC/POPS membrane samples containing diacylglycerols had endothermic transitions in the presence of 200 µM Ca2+ and 5 mM Mg2+. Transitions were not detected when using pure POPS vesicles due to the formation of dehydrated phases as demonstrated by FTIR (Fourier-transform infrared) spectroscopy. PKC α binding studies, performed by differential centrifugation in the presence of 200 µM Ca2+ and 5 mM Mg2+, showed that 1,2-sn-dioleoylglycerol (1,2-DOG) was more effective than 1,3-dioleoylglycerol (1,3-DOG) in promoting binding to POPC/POPS vesicles. However, when pure POPS vesicles were used, PKC α was able to bind to membranes containing either 1,2-DOG or 1,3-DOG to the same extent.

Renal angiotensin II receptors and protein kinase C in diabetic rats: effects of insulin and ACE inhibition

2000 ◽  
Vol 278 (4) ◽  
pp. F603-F612 ◽  
Author(s):  
Farhad Amiri ◽  
Raul Garcia
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Ace Inhibition ◽  
Treated Group ◽  
Diabetic Rats ◽  
Competitive Binding ◽  
Ang Ii ◽  
Binding Studies ◽  
Kinase C ◽  
High Insulin

It has been shown that glomerular ANG II receptors are downregulated and protein kinase C (PKC) activity is enhanced in diabetes mellitus. Therefore, we investigated glomerular and preglomerular vascular ANG II receptors and PKC isoform regulation in streptozotocin (STZ)-diabetic rats treated with insulin and/or captopril. Diabetic rats were prepared by injecting STZ (60 mg/kg). Those that developed diabetes after 48 h were treated with low or high doses of insulin, or with a low dose of insulin as well as captopril, and killed 14 days later. Their glomeruli and preglomerular vessels were purified, competitive binding studies were performed by using the ANG II antagonists losartan and PD-123319, and PKC analysis was carried out by Western blotting. Competitive binding studies showed that the AT1 receptor was the only ANG II receptor detected on both glomeruli and preglomerular vessels of all groups. Preglomerular vascular AT1 receptor density (Bmax) was significantly upregulated in low insulin-treated STZ rats, whereas glomerular AT1 Bmax was downregulated. Furthermore, both the captopril- and high insulin-treated groups had less glomerulosclerosis and vascular damage than the low insulin-treated group. PKCα, PKCδ, PKCε, and PKCμ isoforms found in preglomerular vessels were upregulated by captopril and high insulin doses, respectively, whereas no such regulation occurred in glomeruli. We conclude that in STZ-diabetic rats ANG II receptors and PKC isoforms on preglomerular vessels and glomeruli are differentially regulated by treatment with insulin and/or captopril.

Bidirectional modulation of parathyroid hormone-responsive adenylyl cyclase by protein kinase C

1994 ◽  
Vol 266 (6) ◽  
pp. E897-E904 ◽  
Author(s):  
A. M. Kitten ◽  
T. K. Hymer ◽  
M. S. Katz
Keyword(s):  
Protein Kinase C ◽  
Parathyroid Hormone ◽  
Protein Kinase ◽  
Adenylyl Cyclase ◽  
Catalytic Subunit ◽  
Mrna Levels ◽  
Binding Studies ◽  
Kinase C ◽  
Bidirectional Modulation ◽  
Umr 106

The temporal pattern with which phorbol 12-myristate 13-acetate (PMA), an activator of protein kinase C (PKC), modulates parathyroid hormone (PTH)-responsive adenylyl cyclase (AC) was evaluated in a clonal osteoblast-like cell line (UMR-106). Brief (< or = 1 h) exposure of UMR-106 cells to PMA enhanced PTH stimulation of AC, whereas more prolonged PMA treatment decreased the PTH response, with maximum inhibition occurring at < or = 6 h. PMA treatment also resulted in initial activation followed by downregulation of PKC. Exposure of cells to 1,2-dioctanoyl-sn-glycerol, which activated but did not downregulate PKC, resulted in bidirectional modulation of PTH-responsive AC identical to that produced by PMA. Prolonged PMA exposure decreased PTH receptor number, as determined by radioligand binding studies, and reduced PTH receptor mRNA levels, assessed by Northern blot analysis. Forskolin activation of the catalytic subunit of AC was also decreased after prolonged PMA treatment. The results suggest that activation of PKC sequentially stimulates and then inhibits PTH responsiveness. Inhibition of the PTH response occurs by PKC actions exerted on the PTH receptor and the AC catalytic subunit.

The interaction of pyrene labeled diacylglycerol with protein kinase C in mixed micelles

1993 ◽  
Vol 48 (2) ◽  
pp. 183-191 ◽  
Author(s):  
Philippe I.H. Bastiaens ◽  
Everard H.W. Pap ◽  
Jan-Willem Borst ◽  
Arie van Hoek ◽  
Tadeusz Kulinski ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Mixed Micelles ◽  
Kinase C

scholarly journals Effects of phorbol esters and secretagogues on nitrobenzylthioinosine binding to nucleoside transporters and nucleoside uptake in cultured chromaffin cells

1991 ◽  
Vol 279 (3) ◽  
pp. 651-655 ◽  
Author(s):  
E G Delicado ◽  
R P Sen ◽  
M T Miras-Portugal
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Binding Sites ◽  
Chromaffin Cells ◽  
Phorbol Esters ◽  
Binding Studies ◽  
High Affinity ◽  
Kinase C ◽  
Adenosine Uptake ◽  
Protein Kinase C Activators

Secretagogues inhibited adenosine uptake in chromaffin cells without causing apparent changes in the uptake affinity. The inhibition caused by carbachol, nicotine and acetylcholine reached 50%. This inhibition was reproduced by the action of protein kinase C activators such as phorbol 12-myristate 13-acetate (PMA; 100 nM), phorbol 12,13-dibutyrate (PDBu; 100 nM), dicaproin (10 micrograms/ml) and tricaprylin (10 micrograms/ml), with inhibitions of Vmax. of 18, 20, 37 and 47% respectively. No changes in the affinity of uptake were observed with these effectors. Down-regulation of protein kinase C by phorbol esters decreased the inhibitory effects of carbachol on adenosine uptake. Binding studies with nitrobenzylthioinosine (NBTI) showed a similar decrease in the number of transporters when chromaffin cells were treated with the same effectors used for the uptake studies. The high-affinity dissociation constants showed minor changes with respect to the control. The ratio between maximal uptake capacity and the transporter number per cell was not significantly modified by the action of secretagogues or direct effectors of protein kinase C. The number of high-affinity binding sites for NBTI was decreased in cellular homogenates by the direct action of protein kinase C activators, with staurosporine able to reverse this action. Protein kinase C from bovine brain in the presence of ATP and effectors, decreased the number of high-affinity NBTI-binding sites in purified chromaffin cell plasma membranes. These data suggest the possibility of a molecular modification at the transporter level.

Studies on the mechanism of action of a bilayer stabilizing inhibitor of protein kinase C: Cholesterylphosphoryldimethylethanolamine

1989 ◽  
Vol 9 (3) ◽  
pp. 315-328 ◽  
Author(s):  
Richard M. Epand ◽  
Alan R. Stafford ◽  
Remo Bottega ◽  
Eric H. Ball
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Active Site ◽  
Potent Inhibitor ◽  
Competitive Inhibition ◽  
Inhibition Kinetics ◽  
Kinase C ◽  
Triton X ◽  
Kinetics Of ◽  
Tryptic Hydrolysis

Cholesterylphosphoryldimethylethanolamine is a zwitterionic compound which is a good bilayer stabilizer. As has been found with many other compounds having these properties, cholesterylphosphoryldimethylethanolamine is found to be a potent inhibitor of protein kinase C in both vesicle and micelle assay systems. The kinetics of the inhibition in Triton X-100 micelles was non-competitive with respect to ATP, histone, diolein, phorbol ester and Ca2+. It has a Ki of about 30 μm. The inhibition kinetics as a function of phosphatidylserine concentration is more complex but suggestive of competitive inhibition. Cholesterylphosphoryldimethylethanolamine does not prevent the partitioning of protein kinase C into the membrane. This inhibitor lowers the Ca2+-phosphatidylserine-independent phosphorylation of protamine sulfate by protein kinase C and directly affects the catalytic segment of the enzyme generated by tryptic hydrolysis. Thus, this zwitterionic bilayer stabilizing inhibitor of protein kinase C both competes with the binding of phosphatidylserine as well as affects the active site of protein kinase C.

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