Alteration in liver plasma membrane phospholipids and protein kinase activities during the development of chick embryo.

The changes in phospholipid compositions, membrane fluidity and protein kinase A, protein kinase C, tyrosine and casein kinase activities in chick embryo liver plasma membranes during development have been investigated. The percentage participation of sphingomyelin increased while that of phosphatidylserine decreased during chick embryo development. The alterations in membrane sphingomyelin accompanied an increase of steady-state fluorescence anisotropy (rs) of membrane bilayer. Regression analysis indicated positive linear correlations between the percentage participation of sphingomyelin in total membrane phospholipids and (i) protein kinase C (r = 0.903); (ii) casein kinase (r = 0.936); (iii) protein kinase A (r = 0.850); (iv) tyrosine kinase (r = 0.960) activities. We suggest that sphingomyelin might be an specific activator for all types of protein kinase activities investigation.

Role of rat liver plasma membrane phospholipids in regulation of protein kinase activities.

The role of rat liver plasma membrane phospholipids in the regulation of protein kinase A, protein kinase C and tyrosine kinase activities was investigated. Plasma membrane composition was modified by phospholipase A2, phospholipase C and phospholipase D treatment and subsequent incorporation of various phospholipids. Phospholipase A2 deactivated the three types of protein kinases, while phospholipase C and D affected the enzymes in a different manner. Phosphatidylcholine and sphingomyelin were found to be the most effective activators of protein kinase A and tyrosine kinase. Incorporation of sphingomyelin and phosphatidylserine into partially delipidated plasma membranes resulted in a significant stimulation of protein kinase C activity. Since sphingomyelin appeared to be a specific effector of the three types of protein kinases under investigation, one might suggest that its role in cellular signaling could be manifested via regulation of protein kinase C as well as via modulation of protein kinase A and tyrosine kinase activities.

Casein and tyrosine kinase activities of developing chick embryo liver. Effect of triiodothyronine.

Cytosol cAMP-independent quercetin-inhibited protein kinase of developing chick embryo liver was measured at three embryonic ages (days 12, 14 and 18) in the presence of casein and poly (Glu-Na, Tyr) 4:1 as substrates. In the early embryonic stages the tyrosine kinase was almost as active as casein kinase, but on day 18 the tyrosine phosphorylation was only 25% of the casein phosphorylation. Both kinase activities strongly increased by the end of embryonic development: 7-fold with casein and 2.6-fold with poly (Glu-Na, Tyr) 4:1. Triiodothyronine caused twice the stimulation of casein and tyrosine phosphorylation on day 12, but had no effect on day 18.

Effect of membrane phospholipid composition and fluidity on rat liver plasma membrane tyrosine kinase activity.

1. The effect of membrane phospholipid composition and fluidity on tyrosine kinase activity was investigated in rat liver plasma membranes. 2. The phospholipid composition has been modified by in vitro enrichment of plasma membranes with different phospholipids in the presence of lipid transfer proteins and by partial delipidation with exogenous phospholipases A2, C and D and subsequent enrichment with phosphatidylglycerol. 3. Phosphatidylglycerol and dioleoylglycerophosphocholine caused dramatic elevation of this activity, while phosphatidylserine and phosphatidylethanolamine were less effective. Enrichment with dipalmitoylglycerophosphocholine and sphingomyeline reduced tyrosine kinase activity.

Effect of a sunflower oil-supplemented diet on protein kinase activities of rat liver plasma membranes.

1. The effect of a sunflower oil-enriched diet on plasma membrane-bound protein kinase C, protein kinase A, casein and tyrosine kinase activities was studied. 2. The diet induced an increase in the content of linoleic acid and a decrease in the content of palmitic acid. The anisotropy parameter (rs) of the fluorescence probe DPH and SDPH decreased strongly in the experimental group. 3. Protein kinase C was stimulated more than two times. Tyrosine kinase, protein kinase A and casein kinase activities were increased by 65, 57 and 40%, respectively. 4. We suggest that a more fluid lipid environment favours higher plasma membrane-bound protein kinase activities.

Sphingomyelin-metabolizing enzymes and protein kinase C activity in liver plasma membranes of rats fed with cholesterol-supplemented diet.

The effect of cholesterol-supplemented diet on the activities of rat liver plasma membrane sphingomyelin-metabolizing enzymes and protein kinase C was studied. Protein kinase C, phosphatidylcholine:ceramide-phosphocholine transferase, and phosphatidylethanolamine:ceramide-phosphoethanolamine transferase activities were found to increase continuously and almost in parallel during the experimental period on cholesterol diet (days 10, 20, and 30). Linear regression analysis showed a positive correlation between these activities with correlation coefficients r = 0.959 for protein kinase C and phosphatidylcholine:ceramide-phosphocholine transferase, and r = 0.998 for protein kinase C and phosphatidylethanolamine:ceramide-phosphoethanolamine transferase. On the other hand, protein kinase C activation does not correspond to sphingomyelinase activity changes. These data suggest that protein kinase C activation observed in cholesterol-enriched plasma membranes is due to increased production of diacylglycerol and increased acylation of sphingosine to ceramide.

Effect of triiodothyronine on cAMP-dependent and cAMP-independent protein kinase activities in developing chick embryo liver.

1. Changes in liver cytosol cAMP-dependent kinase and cAMP-independent growth-related quercetin-inhibited casein kinase activities during chick embryo development were studied. 2. Both kinase activities were found to increase continuously during the experimental period. 3. Upon treatment of embryos with triiodothyronine, an activation of cAMP-dependent kinase A and cAMP-independent casein kinase was observed which was most pronounced on days 12 and 14.

Phospholipid-dependence of rat liver plasma membrane protein kinase activities--a new approach.

The influence of the phospholipid composition and fluidity on protein kinase A and protein kinase C activities in rat liver plasma membranes was studied. We observed that enrichment of membranes with phosphatidylglycerol, phosphatidylserine, phosphatidylethanolamine and dioleoylphosphatidylcholine caused activation of both protein kinases. Phosphatidylglycerol was found to be most effective activator. The enrichment of plasma membranes with dipalmitoylphosphatidylcholine and sphingomyelin led to decrease in protein kinase A and C activities. The stimulatory effect of phosphatidylglycerol was confirmed in plasma membranes pretreated with exogenous phospholipases A2, C and D, and subsequently enriched with phosphatidylglycerol. We suggest that besides the specific presence of definite phospholipids protein kinases A and C require a more fluid membrane lipid bilayer to display an optimal activity.