Dual effects of PKNalpha and protein kinase C on phosphorylation of tau protein by glycogen synthase kinase-3beta.
We analyzed the effects of PKNalpha and protein kinase C (PKC) on phosphorylation of tau protein by glycogen synthase kinase (GSK)-3beta using monoclonal antibodies (AT8, AT180, and AT270). These antibodies are highly specific for phosphorylated tau in Alzheimer paired helical filaments, and recognize phosphorylated Ser202/Thr205, Thr231, and Thr181 of tau protein, respectively. Immunoblot analysis demonstrated that PKNalpha and PKC did not directly phosphorylate their sites, whereas GSK-3beta efficiently did so. Incubating GSK-3beta with PKNalpha or PKC subtypes inhibited subsequent GSK-3beta-induced AT8 and AT270 immunoreactivity. However, the constitutive active form of the GSK-3beta(S9A) mutant was almost totally inert to each enzyme. Incubating tau with PKNalpha increased the GSK-3beta-induced AT180 immunoreactivity, which was further enhanced when the S9A mutant was used instead of the wild type GSK-3beta. These results suggest that PKNalpha and PKC directly inhibit GSK-3beta activity at least in part by phosphorylating Ser9 of GSK-3beta, and that they indirectly suppress GSK-3beta-stimulated phosphorylation of tau at amino acids Ser202/Thr205 and Thr181, but enhanced phosphorylation at Thr231 through phosphorylation at other sites of tau.
Isagawa
T
T
Graduate School of Science and Technology, Kobe University, Kobe, 657-8501, Japan.
Mukai
H
H
Oishi
K
K
Taniguchi
T
T
Hasegawa
H
H
Kawamata
T
T
Tanaka
C
C
Ono
Y
Y
D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D001426:Bacterial Proteins; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D000939:Epitopes / Q000276:immunology; D038362:Glycogen Synthase Kinase 3; D038341:Glycogen Synthase Kinases; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D010750:Phosphoproteins / Q000737:chemistry / Q000276:immunology / Q000378:metabolism; D010766:Phosphorylation; D010768:Phosphoserine / Q000276:immunology / Q000378:metabolism; D019000:Phosphotyrosine / Q000276:immunology / Q000378:metabolism; D011493:Protein Kinase C / Q000737:chemistry / Q000378:metabolism*; D011494:Protein Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000276:immunology / Q000378:metabolism; D016875:tau Proteins / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*
D000911:Antibodies, Monoclonal; D001426:Bacterial Proteins; D000939:Epitopes; D010750:Phosphoproteins; D011993:Recombinant Fusion Proteins; D016875:tau Proteins; D010768:Phosphoserine; D019000:Phosphotyrosine; D011494:Protein Kinases; C084887:PknA protein, Nostoc sp. PCC 7120; D038341:Glycogen Synthase Kinases; D011493:Protein Kinase C; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D038362:Glycogen Synthase Kinase 3