scholarly journals Inactivation of glycogen synthase kinase-3β by phosphorylation: new kinase connections in insulin and growth-factor signalling

1993 ◽  
Vol 296 (1) ◽  
pp. 15-19 ◽  
Author(s):  
C Sutherland ◽  
I A Leighton ◽  
P Cohen
Keyword(s):  
Growth Factor ◽  
Protein Kinase ◽  
Glycogen Synthase ◽  
Inhibitory Effect ◽  
Glycogen Synthase Kinase ◽  
Glycogen Synthase Kinase 3 ◽  
Beta Activity ◽  
S6 Kinase ◽  
Growth Factor Signalling ◽  
Phosphatase 2A

The beta-isoform of glycogen synthase kinase-3 (GSK3 beta) isolated from rabbit skeletal muscle was inactivated 90-95% following incubation with MgATP and either MAP kinase-activated protein kinase-1 (MAPKAP kinase-1, also termed RSK-2) or p70 S6 kinase (p70S6K), and re-activated with protein phosphatase 2A. MAPKAP kinase-1 and p70S6K phosphorylated the same tryptic peptide on GSK3 beta, and the site of phosphorylation was identified as the serine located nine residues from the N-terminus of the protein. The inhibitory effect of Ser-9 phosphorylation on GSK3 beta activity was observed with three substrates, (inhibitor-2, c-jun and a synthetic peptide), and also with glycogen synthase provided that 0.15 M KCl was added to the assays. The results suggest that Ser-9 phosphorylation underlies the reported inhibition of GSK3 beta by insulin and that GSK3 may represent a point of convergence of two major growth-factor-stimulated protein kinase cascades.

scholarly journals The mechanism by which epidermal growth factor inhibits glycogen synthase kinase 3 in A431 cells

1994 ◽  
Vol 303 (1) ◽  
pp. 27-31 ◽  
Author(s):  
Y Saito ◽  
J R Vandenheede ◽  
P Cohen
Keyword(s):  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Glycogen Synthase ◽  
Glycogen Synthase Kinase ◽  
Glycogen Synthase Kinase 3 ◽  
A431 Cells ◽  
S6 Kinase ◽  
P70 S6 Kinase ◽  
Epidermal Growth

Glycogen synthase kinase 3 (GSK3) was inhibited by 50% within 5 min when A431 cells were stimulated with epidermal growth factor (EGF). The inhibition was unaffected by rapamycin at concentrations which blocked the activation of p70 S6 kinase, and reversed by incubation with protein phosphatase-1. EGF stimulation of A431 cells inhibited GSK3 alpha and GSK3 beta to a similar extent, and inhibition was accompanied by phosphorylation of the tryptic peptides containing the serine residues phosphorylated in vitro by p70 S6 kinase or MAP kinase-activated protein (MAPKAP) kinase-1 beta (also termed Rsk-2). These results demonstrate that EGF inhibits GSK3 by inducing phosphorylation of a serine residue and that GSK3 is not phosphorylated in vivo by either p70 S6 kinase or protein kinase C.

Analysis of RIM11, a yeast protein kinase that phosphorylates the meiotic activator IME1

1994 ◽  
Vol 14 (12) ◽  
pp. 7909-7919 ◽  
Author(s):  
K S Bowdish ◽  
H E Yuan ◽  
A P Mitchell
Keyword(s):  
Protein Kinase ◽  
Immune Complexes ◽  
Functional Relationship ◽  
Biological Function ◽  
Glycogen Synthase ◽  
Glycogen Synthase Kinase ◽  
Glycogen Synthase Kinase 3 ◽  
Yeast Protein ◽  
Yeast Genes

Many yeast genes that are essential for meiosis are expressed only in meiotic cells. Known regulators of early meiotic genes include IME1, which is required for their expression, and SIN3 and UME6, which prevent their expression in nonmeiotic cells. We report here the molecular characterization of the RIM11 gene, which we find is required for expression of several early meiotic genes. A close functional relationship between RIM11 and IME1 is supported by two observations. First, sin3 and ume6 mutations are epistatic to rim11 mutations; prior studies have demonstrated their epistasis to ime1 mutations. Second, overexpression of RIM11 can suppress an ime1 missense mutation (ime1-L321F) but not an ime1 deletion. Sequence analysis indicates that RIM11 specifies a protein kinase related to rat glycogen synthase kinase 3 and the Drosophila shaggy/zw3 gene product. Three partially defective rim11 mutations alter residues involved in ATP binding or catalysis, and a completely defective rim11 mutation alters a tyrosine residue that corresponds to the site of an essential phosphorylation for glycogen synthase kinase 3. Immune complexes containing a hemagglutinin (HA) epitope-tagged RIM11 derivative, HA-RIM11, phosphorylate two proteins, p58 and p60, whose biological function is undetermined. In addition, HA-RIM11 immune complexes phosphorylate a functional IME1 derivative but not the corresponding ime1-L321F derivative. We propose that RIM11 stimulates meiotic gene expression through phosphorylation of IME1.

scholarly journals Multiple mechanisms for the phosphorylation of C-terminal regulatory sites in rabbit muscle glycogen synthase expressed in COS cells

1996 ◽  
Vol 313 (1) ◽  
pp. 45-50 ◽  
Author(s):  
Alexander V. SKURAT ◽  
Peter J. ROACH
Keyword(s):  
Protein Kinase ◽  
Protein Kinases ◽  
Glycogen Synthase ◽  
Glycogen Synthase Kinase ◽  
Glycogen Synthase Kinase 3 ◽  
Rabbit Muscle ◽  
Cos Cells ◽  
Additional Mutation ◽  
Regulatory Sites

Glycogen synthase can be inactivated by sequential phosphorylation at the C-terminal residues Ser652 (site 4), Ser648 (site 3c), Ser644 (site 3b) and Ser640 (site 3a) catalysed by glycogen synthase kinase-3. In vitro, glycogen synthase kinase-3 action requires that glycogen synthase has first been phosphorylated at Ser656 (site 5) by casein kinase II. Recently we demonstrated that inactivation is linked only to phosphorylation at site 3a and site 3b, and that, in COS cells, modification of these sites can occur by alternative mechanisms independent of any C-terminal phosphorylations [Skurat and Roach (1995) J. Biol. Chem. 270, 12491-12497]. To address these mechanisms multiple Ser → Ala mutations were introduced in glycogen synthase such that only site 3a or site 3b remained intact. Additional mutation of Arg637 → Gln eliminated phosphorylation of site 3a, indicating that Arg637 may be important for recognition of site 3a by its corresponding protein kinase(s). Similarly, additional mutation of Pro645 → Ala eliminated phosphorylation of site 3b, indicating a possible involvement of ‘proline-directed’ protein kinase(s). Mutation of Arg637 alone did not activate glycogen synthase as expected from the loss of phosphorylation at site 3a. Rather, mutation of both Arg637 and the Ser → Ala substitution at site 3b was required for substantial activation. The results suggest that sites 3a and 3b can be phosphorylated independently of one another by distinct protein kinases. However, phosphorylation of site 3b can potentiate phosphorylation of site 3a, by an enzyme such as glycogen synthase kinase-3.

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