Functional involvement of Xenopus LIM kinases in progression of oocyte maturation.
LIM kinases (LIMK), including LIMK1 and LIMK2, are unique LIM-family proteins containing a catalytic (kinase) domain. These kinases phosphorylate an actin-depolymerizing factor, cofilin, involved in the regulation of actin-filament dynamics. An unanswered question is the in vivo function of LIMK and how they contribute to development. When we cloned Xenopus homologues of mammalian LIMK, Xlimk1 and Xlimk2, we found that their mRNA and products were abundantly expressed in oocytes. In addition, we obtained evidence for the functional involvement of Xlimk1/2 during oocyte maturation. The microinjection of Xlimk1/2 mRNA into progesterone-treated oocytes significantly inhibited the appearance of a white maturation spot (WMS), an indicator of entry into meiosis. In oocytes lacking a WMS, the organization and/or migration of the microtubule-derived precursor of the meiotic spindle was predominantly affected. We also found that the ectopic expression of Xlimk1/2 clearly prevented dephosphorylation (activation) of Xenopus cofilin (XAC) during oocyte maturation. Furthermore, co-injection of Xlimk1/2 with the constitutively active type of XAC overcame the inhibitory effects by Xlimk1/2, suggesting that XLIMK-induced abnormality in oocyte maturation was mediated by XAC inactivation. Based on these findings, we propose that XLIMK is a putative regulator of cytoskeletal rearrangements during oocyte maturation, and the interaction between XLIMK activity and microtubule dynamics seems highly likely.
Takahashi
T
T
Division of Biochemistry, Department of Oncology, Biomedical Research Center B7, Osaka University Medical School, Suita, Osaka, 565-0871, Japan.
Koshimizu
U
U
Abe
H
H
Obinata
T
T
Nakamura
T
T
D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D005260:Female; D018507:Gene Expression Regulation, Developmental; D015971:Gene Expression Regulation, Enzymologic; D015723:Gene Library; D006367:HeLa Cells; D006801:Humans; D054461:Lim Kinases; D008969:Molecular Sequence Data; D009865:Oocytes / Q000502:physiology*; D010053:Ovary / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D011374:Progesterone / Q000494:pharmacology; D011494:Protein Kinases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014162:Transfection; D029867:Xenopus Proteins; D014982:Xenopus laevis / Q000235:genetics*; D016335:Zinc Fingers
D004268:DNA-Binding Proteins; D011994:Recombinant Proteins; D029867:Xenopus Proteins; D011374:Progesterone; D011494:Protein Kinases; C515892:LIMK1 protein, human; C102895:LIMK2 protein, human; D054461:Lim Kinases; C490645:Limk2 protein, Xenopus; D017346:Protein Serine-Threonine Kinases