Dephosphorylation of Microtubule Proteins by Brain Protein Phosphatases 1 and 2A, and Its Effect on Microtubule Assembly

Hideyuki Yamamoto, Yoshiki Saitoh, Kohji Fukunaga, Hiroshi Nishimura, Eishichi Miyamoto

Research output: Contribution to journalArticlepeer-review

104 Citations (Scopus)

Abstract

Abstract: Protein phosphatase C was purified 140‐fold from bovine brain with 8% yield using histone H1 phosphorylated by the catalytic subunit of cyclic AMP‐dependent protein kinase (cyclic AMP‐kinase). Brain protein phosphatase C was considered to consist of 10 and 90%, respectively, of the catalytic subunits of protein phosphatases 1 and 2A on the basis of the effects of ATP and inhibitor‐2. Protein phosphatase C dephosphorylated microtubule‐associated protein 2 (MAP2), τ factor, and tubulin phosphorylated by a multifunctional Ca2+/calmodulin‐dependent protein kinase (calmodulin‐kinase) and the catalytic subunit of cyclic AMP‐kinase. The properties of dephosphorylation of MAP2, τ factor, and tubulin were compared. The Km values were in the ranges of 1.6–2.7 μM for MAP2 and τ factor. The Km value for tubulin decreased from 25 to 10–12.5 μM in the presence of 1.0 μM Mn2+. No difference in kinetic properties of dephosphorylation was observed between the substrates phosphorylated by the two kinases. Protein phosphatase C did not dephosphorylate the native tubulin, but universally dephosphorylated tubulin phosphorylated by the two kinases. The holoenzyme of protein phosphatase 2A from porcine brain could also dephosphorylate MAP2, τ factor, and tubulin phosphorylated by the two kinases. The phosphorylation of MAP2 and τ factor by calmodulin‐kinase separately induced the inhibition of microtubule assembly, and the dephosphorylation by protein phosphatase C removed its inhibitory effect. These data suggest that brain protein phosphatases 1 and 2A are involved in the switch‐off mechanism of both Ca2+/calmodulin‐dependent and cyclic AMP‐dependent regulation of microtubule formation.

Original languageEnglish
Pages (from-to)1614-1623
Number of pages10
JournalJournal of Neurochemistry
Volume50
Issue number5
DOIs
Publication statusPublished - 1988 May
Externally publishedYes

Keywords

  • Ca/calmodulin‐dependent protein kinase
  • Cyclic AMP‐dependent protein kinase
  • Microtubule‐associated protein 2
  • Protein phosphatase
  • Tubulin
  • τ factor

ASJC Scopus subject areas

  • Biochemistry
  • Cellular and Molecular Neuroscience

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