Phosphorylation and inactivation of rat liver glycogen synthase by cAMP-dependent protein kinase and cAMP-independent synthase (casein) kinase-1.

A Ca2+-pump ATPase, similar to that in the endoplasmic reticulum, has been located on the outer membrane of rat liver nuclei. The effect of cAMP-dependent protein kinase (PKA) on nuclear Ca2+-ATPase (NCA) was studied by using purified rat liver nuclei. Treatment of isolated nuclei with the catalytic unit of PKA resulted in the phosphorylation of a 105-kDa band that was recognized by antibodies specific for sarcoplasmic reticulum Ca2+-ATPase type 2b. Partial purification and immunoblotting confirmed that the 105-kDa protein band phosphorylated by PKA is NCA. The stoichiometry of phosphorylation was 0.76 mol of phosphate incorporated/mol of partially purified enzyme. Measurement of ATP-dependent 45Ca2+ uptake into purified nuclei showed that PKA phosphorylation enhanced the Ca2+-pumping activity of NCA. We show that PKA phosphorylation of Ca2+-ATPase enhances the transport of 10-kDa fluorescent-labeled dextrans across the nuclear envelope. The findings reported in this paper are consistent with the notion that the crosstalk between the cAMP/PKA- and Ca2+-dependent signaling pathways identified at the cytoplasmic level extends to the nucleus. Furthermore, these data support a function for crosstalk in the regulation of calcium-dependent transport across the nuclear envelope.

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Protein phosphatases active on acetyl-CoA carboxylase phosphorylated by casein kinase I, casein kinase II and the cAMP-dependent protein kinase

Biochemical and Biophysical Research Communications ◽

10.1016/0006-291x(85)91733-4 ◽

1985 ◽

Vol 130 (3) ◽

pp. 1132-1138 ◽

Cited By ~ 10

Author(s):

Lee A. Witters ◽

Geoffrey W. Bacon

Keyword(s):

Protein Kinase ◽

Protein Phosphatases ◽

Casein Kinase Ii ◽

Casein Kinase ◽

Acetyl Coa Carboxylase ◽

Casein Kinase I ◽

Dependent Protein Kinase ◽

Acetyl Coa ◽

Camp Dependent Protein Kinase ◽

Dependent Protein

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EFFECTS OF SEPSIS ON cAMP DEPENDENT PROTEIN KINASE A (PKA) ACTIVITY IN RAT LIVER

Shock ◽

10.1097/00024382-199506000-00154 ◽

1995 ◽

Vol 3 (6) ◽

pp. 44

Author(s):

K. Andrejko ◽

C. Deutschman

Keyword(s):

Protein Kinase ◽

Protein Kinase A ◽

Rat Liver ◽

Dependent Protein Kinase ◽

Camp Dependent Protein Kinase ◽

Dependent Protein ◽

Kinase A

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Effects of vanadate on protein kinases in rat hepatocytes

Biochemical Journal ◽

10.1042/bj2620563 ◽

1989 ◽

Vol 262 (2) ◽

pp. 563-567 ◽

Cited By ~ 7

Author(s):

C Villar-Palasi ◽

J J Guinovart ◽

A M Gómez-Foix ◽

J E Rodriguez-Gil ◽

F Bosch

Keyword(s):

Protein Kinase ◽

Cyclic Amp ◽

Kinase Activity ◽

Activity Ratio ◽

Glycogen Synthase ◽

Rat Hepatocytes ◽

Casein Kinase ◽

Optimal Time ◽

Dependent Protein Kinase ◽

Dependent Protein

In rat hepatocytes, vanadate modifies neither the intracellular concentration of cyclic AMP nor the -cyclic AMP/+cyclic AMP activity ratio for cyclic AMP-dependent protein kinase. Vanadate can, however, counteract the increase in cyclic AMP and the increase in the -cyclic AMP/+cyclic AMP activity ratio of cyclic AMP-dependent protein kinase induced by glucagon. On the other hand, vanadate treatment of hepatocytes can produce a time- and concentration-dependent increase in cyclic AMP- and Ca2+-independent casein kinase activity. Maximal activation at the optimal time with 5 mM-vanadate was about 70% over control. A clear relationship was observed between the activation of casein kinase and the inactivation of glycogen synthase after vanadate treatment. These results suggest that casein kinase activity may be involved in vanadate actions in rat hepatocytes.

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