TY - JOUR
T1 - MAP kinase becomes stably activated at metaphase and is associated with microtubule-organizing centers during meiotic maturation of mouse oocytes
AU - Verlhac, Marie Hélène
AU - De Pennart, Henri
AU - Maro, Bernard
AU - Cobb, Melante H.
AU - Clarke, Hugh J.
N1 - Copyright:
Copyright 2017 Elsevier B.V., All rights reserved.
PY - 1993/8
Y1 - 1993/8
N2 - Using antisera generated against sequences conserved between the ERK1- and the ERK2-encoded species of mitogen-activated protein (MAP) kinases of the rat, species of approximate Mr 42 and 44 kDa were identified in mouse oocytes. When oocytes underwent meiotic maturation, both species displayed a retarded electrophoretic mobility, consistent with modification by phosphorylation. The slow-migrating forms first appeared after the oocytes had entered metaphase, and their appearance was sensitive to inhibitors of protein synthesis or phosphorylation. These forms remained throughout maturation and in oocytes arrested at metaphase II. Following oocyte activation, which induces a transition to interphase, the slow-migrating forms were replaced by the fast-migrating forms observed in prophase oocytes. MAP kinase activity also increased after oocytes entered metaphase, and this increase required protein synthesis and phosphorylation. To investigate the intracellular distribution of the immunoreactive species, spindles were purified from metaphase II eggs. Both the 42- and the 44-kDa species were detected in immunoblots, and bright staining of the spindle poles was observed by immunofluorescence. When intact oocytes undergoing maturation were examined by immunofluorescence, foci of staining were initially detected on opposing sides of the condensing chromosomes and then became congregated at each pole of the first meiotic spindle. No localized staining was observed during the first meiotic division, but stained foci were present at the poles of the second meiotic spindle. In addition, several cytoplasmic foci of staining often could be seen. When oo-cytes were exposed to taxol, which permits nonspindle microtubule-organizing centers (MTOCs) present in the cytoplasm to nucleate micro tubule assembly, the cytoplasmic foci labeled by the MAP kinase antibodies were found to contain tubulin. We conclude that mouse oocytes contain 42- and 44-kDa species of MAP kinase and that, after maturing oocytes enter metaphase, MAP kinase activity is stimulated by means of a process requiring protein synthesis and phosphorylation. MAP kinase is present in the spindle and is specifically associated with the MTOCs present at the spindle poles and in the cytoplasm. Evidence from cell-free systems suggests that the alterations in MTOC activity that normally occur at metaphase in oocytes may be regulated by MAP kinase. The association of MAP kinase with MTOCs provides a potential structural basis for this cell cycle-dependent change in MTOC activity.
AB - Using antisera generated against sequences conserved between the ERK1- and the ERK2-encoded species of mitogen-activated protein (MAP) kinases of the rat, species of approximate Mr 42 and 44 kDa were identified in mouse oocytes. When oocytes underwent meiotic maturation, both species displayed a retarded electrophoretic mobility, consistent with modification by phosphorylation. The slow-migrating forms first appeared after the oocytes had entered metaphase, and their appearance was sensitive to inhibitors of protein synthesis or phosphorylation. These forms remained throughout maturation and in oocytes arrested at metaphase II. Following oocyte activation, which induces a transition to interphase, the slow-migrating forms were replaced by the fast-migrating forms observed in prophase oocytes. MAP kinase activity also increased after oocytes entered metaphase, and this increase required protein synthesis and phosphorylation. To investigate the intracellular distribution of the immunoreactive species, spindles were purified from metaphase II eggs. Both the 42- and the 44-kDa species were detected in immunoblots, and bright staining of the spindle poles was observed by immunofluorescence. When intact oocytes undergoing maturation were examined by immunofluorescence, foci of staining were initially detected on opposing sides of the condensing chromosomes and then became congregated at each pole of the first meiotic spindle. No localized staining was observed during the first meiotic division, but stained foci were present at the poles of the second meiotic spindle. In addition, several cytoplasmic foci of staining often could be seen. When oo-cytes were exposed to taxol, which permits nonspindle microtubule-organizing centers (MTOCs) present in the cytoplasm to nucleate micro tubule assembly, the cytoplasmic foci labeled by the MAP kinase antibodies were found to contain tubulin. We conclude that mouse oocytes contain 42- and 44-kDa species of MAP kinase and that, after maturing oocytes enter metaphase, MAP kinase activity is stimulated by means of a process requiring protein synthesis and phosphorylation. MAP kinase is present in the spindle and is specifically associated with the MTOCs present at the spindle poles and in the cytoplasm. Evidence from cell-free systems suggests that the alterations in MTOC activity that normally occur at metaphase in oocytes may be regulated by MAP kinase. The association of MAP kinase with MTOCs provides a potential structural basis for this cell cycle-dependent change in MTOC activity.
UR - http://www.scopus.com/inward/record.url?scp=0027258955&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0027258955&partnerID=8YFLogxK
U2 - 10.1006/dbio.1993.1192
DO - 10.1006/dbio.1993.1192
M3 - Article
C2 - 8344454
AN - SCOPUS:0027258955
SN - 0012-1606
VL - 158
SP - 330
EP - 340
JO - Developmental Biology
JF - Developmental Biology
IS - 2
ER -