Tau protein is phosphorylated by cyclic AMP-dependent protein kinase and calcium/calmodulin-dependent protein kinase II within its microtubule-binding domains at Ser-262 and Ser-356.
Phosphorylation of tau protein at Ser-262 has been shown to diminish its ability to bind to taxol-stabilized microtubules. The paired helical filaments (PHFs) found in Alzheimer's disease brain are composed of PHF-tau, which is hyperphosphorylated at multiple sites including Ser-262. However, protein kinase(s) able to phosphorylate this site are still under investigation. In this study, the ability of cyclic AMP-dependent protein kinase (cAMP-PK) and calcium/calmodulin-dependent protein kinase II (CaMKII) to phosphorylate tau at Ser-262, as well as Ser-356, is demonstrated by use of a monoclonal antibody (12E8) which has been shown to recognize tau when these sites are phosphorylated. Cleavage of cAMP-PK-phosphorylated tau at cysteine residues by 2-nitro-5-thiocyanobenzoic acid, which cuts the protein into essentially two fragments and separates Ser-262 from Ser-356, revealed that cAMP-PK phosphorylates both Ser-262 and Ser-356. In addition, phosphorylation with cAMP-PK or CaMKII of recombinant tau in which Ser-262, Ser-356 or both had been mutated to alanines, clearly demonstrated that cAMP-PK and CaMKII were able to phosphorylate both sites. Mitogen-activated protein kinase or protein kinase C did not phosphorylate tau at Ser-262 and/or Ser-356. Finally, evidence is presented that phosphorylation of both these sites occurs in cultured nerve cells under certain conditions, indicating their potential physiological relevance.
Litersky
J M
JM
Department of Psychiatry, University of Alabama at Birmingham 35294-0017, USA.
Johnson
G V
GV
Jakes
R
R
Goedert
M
M
Lee
M
M
Seubert
P
P
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D015153:Blotting, Western; D001921:Brain / Q000378:metabolism; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002417:Cattle; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D007527:Isoenzymes / Q000737:chemistry / Q000378:metabolism; D008870:Microtubules / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D010766:Phosphorylation; D051381:Rats; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012694:Serine / Q000378:metabolism; D013861:Thiocyanates / Q000378:metabolism; D016875:tau Proteins / Q000378:metabolism*
D004791:Enzyme Inhibitors; D007527:Isoenzymes; D011994:Recombinant Proteins; D013861:Thiocyanates; D016875:tau Proteins; D012694:Serine; D017868:Cyclic AMP-Dependent Protein Kinases; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases; C008658:2-nitro-5-thiocyanobenzoic acid