tailieunhanh - Báo cáo khoa học: Inhibitors of protein phosphatase 1 and 2A decrease the level of tubulin carboxypeptidase activity associated with microtubules

The association of tubulin carboxypeptidase with micro-tubules may be involved in the determination of the tyrosi-nation state of the microtubules, . their proportion of tyrosinated vs. nontyrosinated tubulin. We investigated the role of protein phosphatases in the association of carb-oxypeptidase with microtubules in COS cells. Okadaic acid and other PP1/PP2A inhibitors, when added to culture medium before isolation of the cytoskeletal fraction, pro-duced near depletion of the carboxypeptidase activity asso-ciated with microtubules. . | Eur. J. Biochem. 270 4921-4929 2003 FEBS 2003 doi Inhibitors of protein phosphatase 1 and 2A decrease the level of tubulin carboxypeptidase activity associated with microtubules Maria A. Contin Silvia A. Purro C. Gaston Bisig Hector S. Barra and Carlos A. Arce Centro de Investigaciones en Quimica Biologica de Cordoba CIQUIBIC UNC-CONICET Departamento de Quimica Biologica Facultad de Ciencias Quimicas Universidad Nacional de Cordoba Argentina The association of tubulin carboxypeptidase with microtubules may be involved in the determination of the tyrosi-nation state of the microtubules . their proportion of tyrosinated vs. nontyrosinated tubulin. We investigated the role of protein phosphatases in the association of carboxypeptidase with microtubules in COS cells. Okadaic acid and other PP1 PP2A inhibitors when added to culture medium before isolation of the cytoskeletal fraction produced near depletion of the carboxypeptidase activity associated with microtubules. Isolation of the native assembled and nonassembled tubulin fractions from cells treated and not treated with okadaic acid and subsequent in vitro assay of the carboxypeptidase activity revealed that the enzyme was dissociated from microtubules by okadaic acid treatment and recovered in the soluble fraction. There was no effect by nor-okadaone an inactive okadaic acid analogue or inhibitors of PP2B and of tyrosine phosphatases which do not affect PP1 PP2A activity. When tested in an in vitro system okadaic acid neither dissociated the enzyme from microtubules nor inactivated it. In living cells prior stabilization of microtubules with taxol prevented the dissociation of carboxypeptidase by okadaic acid indicating that dynamic microtubules are needed for okadaic acid to exert its effect. On the other hand stabilization of microtubules subsequent to okadaic acid treatment did not reverse the dissociating effect of okadaic acid. These results suggest that dephosphorylation

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