Ca(2+)/calmodulin-dependent protein kinase II is stimulated by Wnt and Frizzled homologs and promotes ventral cell fates in Xenopus.
Wnt ligands working through Frizzled receptors have a differential ability to stimulate release of intracellular calcium (Ca(2+)) and activation of protein kinase C (PKC). Since targets of this Ca(2+) release could play a role in Wnt signaling, we first tested the hypothesis that Ca(2+)/calmodulin-dependent protein kinase II (CamKII) is activated by some Wnt and Frizzled homologs. We report that Wnt and Frizzled homologs that activate Ca(2+) release and PKC also activate CamKII activity in Xenopus embryos, while Wnt and Frizzled homologs that activate beta-catenin function do not. This activation occurs within 10 min after receptor activation in a pertussis toxin-sensitive manner, concomitant with autophosphorylation of endogenous CamKII. Based on data that Wnt-5A and Wnt-11 are present maternally in Xenopus eggs, and activate CamKII, we then tested the hypothesis that CamKII participates in axis formation in the early embryo. Measurements of endogenous CamKII activity from dorsal and ventral regions of embryos revealed elevated activity on the prospective ventral side, which was suppressed by a dominant negative Xwnt-11. If this spatial bias in CamKII activity were involved in promoting ventral cell fate one might predict that elevating CamKII activity on the dorsal side would inhibit dorsal cell fates, while reducing CamKII activity on the ventral side would promote dorsal cell fates. Results obtained by expression of CamKII mutants were consistent with this prediction, revealing that CamKII contributes to a ventral cell fate.
Kühl
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Howard Hughes Medical Institute, Department of Pharmacology and Center for Developmental Biology, University of Washington School of Medicine, Seattle, Washington 98195, USA.
Sheldahl
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Malbon
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Moon
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D000818:Animals; D015153:Blotting, Western; D001921:Brain / Q000201:enzymology; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D019070:Cell Lineage; D016764:Cell Polarity; D003598:Cytoskeletal Proteins / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D004789:Enzyme Activation; D051157:Frizzled Receptors; D050989:GATA2 Transcription Factor; D018398:Homeodomain Proteins / Q000378:metabolism; D005810:Multigene Family; D011233:Precipitin Tests; D011493:Protein Kinase C / Q000378:metabolism; D011506:Proteins / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D015347:RNA Probes / Q000378:metabolism; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015398:Signal Transduction; D020825:T-Box Domain Proteins / Q000378:metabolism; D015534:Trans-Activators; D014157:Transcription Factors / Q000378:metabolism; D051153:Wnt Proteins; D014981:Xenopus / Q000196:embryology* / Q000235:genetics*; D029867:Xenopus Proteins; D029961:Zebrafish Proteins; D051176:beta Catenin
C495266:CTNNB1 protein, Xenopus; C495268:Ctnnb1 protein, rat; D003598:Cytoskeletal Proteins; D004268:DNA-Binding Proteins; D051157:Frizzled Receptors; D050989:GATA2 Transcription Factor; C494714:GATA2 protein, Xenopus; C494713:Gata2 protein, rat; D018398:Homeodomain Proteins; D011506:Proteins; D011518:Proto-Oncogene Proteins; D015347:RNA Probes; D011993:Recombinant Fusion Proteins; D020825:T-Box Domain Proteins; C116765:TBXT protein, Xenopus; D015534:Trans-Activators; D014157:Transcription Factors; D051153:Wnt Proteins; D029867:Xenopus Proteins; D029961:Zebrafish Proteins; D051176:beta Catenin; C112507:ventx1.2 protein, Xenopus; C099992:ventx2.1 protein, Xenopus; D011493:Protein Kinase C; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases