Protein kinase C and progesterone-induced maturation in Xenopus oocytes

Development ◽  
1990 ◽  
Vol 109 (3) ◽  
pp. 597-604
Author(s):  
R.L. Varnold ◽  
L.D. Smith
Keyword(s):  
Cell Cycle ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Xenopus Oocytes ◽  
Plasma Membranes ◽  
Protein Kinase C Inhibitors ◽  
Kinase C ◽  
Protein Kinase C Activity ◽  
Concomitant Reduction ◽  
Dependent Protein

Though progesterone-induced maturation has been studied extensively in Xenopus oocytes, the mechanism whereby the prophase block arrest is released is not well understood. The current hypothesis suggests that a reduction in cAMP and subsequent inactivation of cAMP-dependent protein kinase is responsible for reentry into the cell cycle. However, several lines of evidence indicate that maturation can be induced without a concomitant reduction in cAMP. We show that the mass of diacylglycerol in whole oocytes and plasma membranes decreases 29% and 10% respectively, within the first 15 sec after the addition of progesterone. Diacylglycerol in plasma membranes further decreased 59% by 5 min. We also show that the protein kinase C inhibitors sphingosine and staurosporine can induce oocyte maturation. In addition, the synthetic diglyceride, DiC8, and microinjected PKC can inhibit or delay progesterone-induced maturation. These results together suggest that a transient decrease in protein kinase C activity may regulate entry into the cell cycle. The mechanism whereby DAG is decreased in response to progesterone is unclear. Initial studies show that progesterone leads to a decrease in IP3 suggesting that progesterone may act by reducing the hydrolysis of PIP2. On the other hand, progesterone caused a decrease in the amount of [3H]arachidonate labelling in DAG during the same time suggesting that progesterone may stimulate lipase activity. The relationship between postulated changes in the PKC pathway and those hypothesized for the PKA pathway are discussed.

scholarly journals Phosphorylation of membrane proteins in erythrocytes treated with lead

1996 ◽  
Vol 315 (2) ◽  
pp. 401-406 ◽  
Author(s):  
Luisa BELLONI-OLIVI ◽  
Madhu ANNADATA ◽  
Gary W. GOLDSTEIN ◽  
Joseph P. BRESSLER
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Membrane Proteins ◽  
Lead Acetate ◽  
Direct Interaction ◽  
Cytoskeletal Proteins ◽  
Human Erythrocytes ◽  
Kinase C ◽  
Protein Kinase C Activity ◽  
Dependent Protein

In immature rat microvessels, endothelial cells and glioma cells, exposure to lead results in an increase in the level of protein kinase C in membranes. In this paper we have extended these studies to human erythrocytes and, in addition, studied the phosphorylation of membrane proteins. A significant increase in the phosphorylation of membrane cytoskeletal proteins of molecular mass 120, 80, 52 and 45 kDa was observed in human erythrocytes treated for 60 min with lead acetate at concentrations greater than 100 nM. These same proteins were phosphorylated when erythrocytes were treated for 10 min with 50 nM phorbol 12-myristate 13-acetate (PMA). Similarly, protein kinase C activity was elevated and an increase in the amount of protein kinase C-α was observed in membranes from erythrocytes exposed to concentrations of lead acetate above 100 nM. No changes, however, in the activities of cAMP-dependent protein kinase, protein phosphatases I and IIA or casein kinase were observed. Phosphorylation of these membrane proteins stimulated by lead acetate or by PMA was not observed in erythrocytes depleted of protein kinase C by a 72-h treatment with 500 nM phorbol 12,13-dibutyrate. Finally, no changes in the levels of calcium or diacylglycerol were observed in erythrocytes stimulated with 100 nM lead acetate. These results indicate that, in erythrocytes, lead acetate stimulates the phosphorylation of membrane cytoskeletal proteins by a mechanism dependent on protein kinase C. Since levels of calcium or diacylglycerols did not increase, it appears that lead may activate the enzyme by a direct interaction.

Trypsin stimulation of aldosterone and 18-hydroxycorticosterone production by rat adrenal zona glomerulosa tissue is mediated by activation of protein kinase C

1990 ◽  
Vol 5 (1) ◽  
pp. 85-93 ◽  
Author(s):  
G. P. Vinson ◽  
S. M. Laird ◽  
J. P. Hinson ◽  
N. Mallick ◽  
S. Marsigliante ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Phospholipase C ◽  
Polymyxin B ◽  
Zona Glomerulosa ◽  
Protein Kinase C Inhibitors ◽  
Kinase C ◽  
Protein Kinase C Activity ◽  
Tissue Sensitivity ◽  
Protein Components

ABSTRACT When rat adrenal whole capsules, containing the zona glomerulosa, were incubated, addition of the protein kinase C inhibitors TMB-8 (10 μmol/l), W7, H7, polymyxin-B and sphingosine (all 1 μmol/l) was found to inhibit the steroidogenic response to trypsin. Aldosterone and 18-hydroxycorticosterone were strongly, and corticosterone moderately, affected, while the production of 18-hydroxydeoxycorticosterone was neither stimulated by trypsin nor inhibited by the protein kinase C inhibitors. Addition of neomycin, which prevents substrate interaction with phospholipase C, also inhibited the response to trypsin, while addition of phospholipase C itself stimulated aldosterone, 18-hydroxycorticosterone and corticosterone production with the same tissue sensitivity as trypsin. Addition of phospholipase A2 had no effect. Direct assay of protein kinase C activity showed that trypsin stimulation effected the translocation of Ca2+/phospholipid-activated protein kinase C from the cytosolic to the membrane fraction. When glomerulosa tissue was incubated with [32P]ATP, and cytosolic proteins were subjected to isoelectric focusing on polyacrylimide gels, autoradiography showed that incorporation of 32P into several protein components was increased by trypsin stimulation. It was concluded that trypsin exerts its stimulatory effects on steroidogenesis by activating protein kinase C; not, however, by generating the Ca2+/phospholipid-independent fragment, but possibly by enhancing the activity of phospholipase C.

scholarly journals Involvement of calcium-sensitive phospholipid-dependent protein kinase in control of acid secretion by isolated rat parietal cells

1985 ◽  
Vol 232 (2) ◽  
pp. 609-611 ◽  
Author(s):  
N G Anderson ◽  
P J Hanson
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Acid Secretion ◽  
Phorbol Esters ◽  
Inhibitory Effect ◽  
Dependent Protein Kinase ◽  
Kinase C ◽  
Protein Kinase C Activity ◽  
Dependent Protein ◽  
Isolated Rat

The relative potency with which phorbol esters inhibited histamine-stimulated aminopyrine accumulation (an index of acid secretion) paralleled that which has been established for the activation of purified protein kinase C. The inhibitory effect of 1-oleoyl-2-acetylglycerol on aminopyrine accumulation stimulated by various secretagogues was similar to that of 12-O-tetradecanoylphorbol 13-acetate. Protein kinase C activity was present in a parietal-cell-enriched fraction. In conclusion, protein kinase C could be involved in mechanisms regulating gastric acid secretion.

Sign in / Sign up

Export Citation Format

Share Document