Respective roles of protein tyrosine kinases and protein kinases C in the upregulation of beta-catenin distribution, and compaction in mouse preimplantation embryos: a pharmacological approach.
The cellular distribution of beta-catenin was determined by western blotting and laser confocal scanning microscopy in both control and pharmacologically-manipulated mouse preimplantation embryos. Most of the stored maternal beta-catenin is Triton X-100-extractable and distributed throughout the cytoplasm. In 2-cell stage embryos, the remaining molecules are concentrated in regions of cell contact and, to a lesser extent, at non apposed surfaces. Association of beta-catenin with the cortex of non apposed membranes decreases as cleavage proceeds, and is lost at compaction. In contrast to the rapid cross-linking of cell surfaces induced by wheat germ agglutinin, the diacylglyceride-induced compaction-like adhesion of 2- and 4-cell embryos correlates with complete restriction of beta-catenin to the apposing membranes. On the contrary, tyrphostin B46, a specific protein tyrosine kinase inhibitor, fails to induce both premature beta-catenin relocalisation and compaction. In addition, we show that orthovanadate induces a dramatic increase in the level of phosphotyrosine labelling of cell-cell junctions in compacted 8-cell stage embryos without inducing their decompaction. However, most of these orthovanadate tyrosine-phosphorylated proteins are detergent-soluble, while beta-catenin restricted to the apposing membranes is not. In conclusion, our results confirm that diacylglycerol-dependent kinases upregulate both beta-catenin redistribution and compaction, and indicate that neither tyrosine kinases, nor tyrosine phosphatases are critical for the proper onset of compaction which seems, in addition, not causally linked to tyrosine dephosphorylation of beta-catenin.
Service de biologie et embryologie, faculté de médecine et de pharmacie, université de Mons-Hainaut, Mons, Belgium.
J J
JJ
Goval
A
A
Van Cauwenberge
H
H
Alexandre
D000818:Animals; D001755:Blastocyst / Q000166:cytology / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D002448:Cell Adhesion / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism; D048429:Cell Size / Q000187:drug effects; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D003599:Cytoskeleton / Q000378:metabolism; D004075:Diglycerides / Q000494:pharmacology; D005260:Female; D015151:Immunoblotting; D008297:Male; D051379:Mice; D008856:Microscopy, Fluorescence; D017830:Octoxynol / Q000737:chemistry; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D015534:Trans-Activators; D014638:Vanadates / Q000494:pharmacology / Q000633:toxicity; D051176:beta Catenin
C495267:CTNNB1 protein, mouse; D003598:Cytoskeletal Proteins; D004075:Diglycerides; D015534:Trans-Activators; D051176:beta Catenin; D014638:Vanadates; C038237:1-oleoyl-2-acetylglycerol; D017830:Octoxynol; D011505:Protein-Tyrosine Kinases; D011493:Protein Kinase C