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Inhibitors of protein phosphatase 1 and 2A decrease the level of tubulin carboxypeptidase activity associated with

María A Contín1, Silvia A Purro, C Gastón Bisig

  • 1Centro de Investigaciones en Química Biológica de Córdoba, CIQUIBIC (UNC-CONICET), Departamento de Química Biológica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Argentina.

European Journal of Biochemistry
|December 5, 2003
PubMed

Insights

Protein phosphatases regulate tubulin carboxypeptidase association with microtubules. Inhibitors like okadaic acid cause dissociation, suggesting phosphorylation controls enzyme binding to dynamic microtubules.

Area of Science:

  • Cell Biology
  • Biochemistry
  • Cytoskeleton Dynamics

Background:

  • Tubulin carboxypeptidase activity is linked to microtubule tyrosination.
  • The regulation of tubulin carboxypeptidase association with microtubules remains unclear.

Purpose of the Study:

  • To investigate the role of protein phosphatases in tubulin carboxypeptidase binding to microtubules.
  • To determine how microtubule dynamics influence this association.

Main Methods:

  • Treatment of COS cells with protein phosphatase inhibitors (okadaic acid).
  • Isolation of cytoskeletal and soluble fractions.
  • In vitro and in vivo assays of tubulin carboxypeptidase activity.
  • Microtubule stabilization using taxol.

Main Results:

  • Okadaic acid and PP1/PP2A inhibitors depleted microtubule-associated carboxypeptidase activity.
  • Carboxypeptidase dissociated from microtubules and recovered in the soluble fraction upon okadaic acid treatment.
  • Dynamic microtubules are required for okadaic acid to induce dissociation; stabilization post-treatment did not reverse the effect.
  • PP2B and tyrosine phosphatase inhibitors had no effect.

Conclusions:

  • Dephosphorylation, likely of the enzyme or an intermediate, regulates tubulin carboxypeptidase association with microtubules.
  • Phosphorylation state dictates the enzyme's ability to bind to microtubules.
  • Microtubule dynamics are crucial for this regulatory process.

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