Phosphorylation of tau by proline-directed protein kinase (p34cdc2/p58cyclin A) decreases tau-induced microtubule assembly and antibody SMI33 reactivity

Clay W. Scott, Philip R Vulliet, Claudia B. Caputo

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35 Scopus citations


Tau protein was evaluated as a substrate for a proline-directed protein kinase (p34cdc2/p58cyclin A) which recognizes the phosphorylation site motif X-Ser/Thr-Pro-X. The shortest human tau isoform, expressed as a recombinant protein, was phosphorylated to a stoichiometry of 2 mol phosphate/mol tau. Phosphoamino acid analysis revealed phosphorylation of both serine and threonine residues. Phosphorylation of recombinant tau resulted in a decreased ability to induce microtubule assembly but had no effect on the final extent of microtubule formation or on the rate of cold-induced microtubule disassembly. Phosphorylation of tau by the proline-directed protein kinase completely blocked immunoreactivity with antibody SMI33. Phosphorylation did not create the epitopes for the phosphate-dependent antibodies SMI31 or SMI34. Antibody SMI33 recognizes neurofibrillary tangles after treatment with alkaline phosphatase, suggesting that the proline-directed protein kinase may phosphorylate tau at sites that are phosphorylated in Alzheimer's disease.

Original languageEnglish (US)
Pages (from-to)237-242
Number of pages6
JournalBrain Research
Issue number2
StatePublished - May 21 1993


  • Alzheimer's disease
  • Cytoskeleton
  • Microtubule-associated protein

ASJC Scopus subject areas

  • Developmental Biology
  • Molecular Biology
  • Clinical Neurology
  • Neuroscience(all)


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