title: Nucleotide exchange factor ECT2 interacts with the polarity protein complex Par6/Par3/protein kinase Czeta (PKCzeta) and regulates PKCzeta activity.
abstract: Regulation of cell polarity is an important biological event that governs diverse cell functions such as localization of embryonic determinants and establishment of tissue and organ architecture. The Rho family GTPases and the polarity complex Par6/Par3/atypical protein kinase C (PKC) play a key role in the signaling pathway, but the molecules that regulate upstream signaling are still not known. Here we identified the guanine nucleotide exchange factor ECT2 as an activator of the polarity complex. ECT2 interacted with Par6 as well as Par3 and PKCzeta. Coexpression of Par6 and ECT2 efficiently activated Cdc42 in vivo. Overexpression of ECT2 also stimulated the PKCzeta activity, whereas dominant-negative ECT2 inhibited the increase in PKCzeta activity stimulated by Par6. ECT2 localization was detected at sites of cell-cell contact as well as in the nucleus of MDCK cells. The expression and localization of ECT2 were regulated by calcium, which is a critical regulator of cell-cell adhesion. Together, these results suggest that ECT2 regulates the polarity complex Par6/Par3/PKCzeta and possibly plays a role in epithelial cell polarity.
authors.affiliation: Molecular Tumor Biology Section, Laboratory of Cell Biology, National Cancer Institute, Building 37, Room 2144, 37 Convent Dr., MSC 4255, Bethesda, MD 20892-4255, USA.
authors.forename: Xiu-Fen
authors.initials: XF
authors.lastname: Liu
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ishida
authors.forename: Razi
authors.initials: R
authors.lastname: Raziuddin
authors.forename: Toru
authors.initials: T
authors.lastname: Miki
mesh_terms: D000818:Animals; D015153:Blotting, Western; D019556:COS Cells; D002448:Cell Adhesion; D002460:Cell Line; D004285:Dogs; D004847:Epithelial Cells / Q000378:metabolism; D005799:Genes, Dominant; D005822:Genetic Vectors; D006367:HeLa Cells; D006801:Humans; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D011233:Precipitin Tests; D011485:Protein Binding; D011493:Protein Kinase C / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism / Q000502:physiology*; D034741:RNA, Small Interfering / Q000378:metabolism; D018179:Receptors, Thrombin / Q000378:metabolism*; D020798:Two-Hybrid System Techniques; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism; D020830:rac1 GTP-Binding Protein / Q000378:metabolism; D000099221:Protein Kinase C zeta
chemical_list: D011493:Protein Kinase C; D011506:Proteins; D011518:Proto-Oncogene Proteins; D034741:RNA, Small Interfering; D018179:Receptors, Thrombin; D020764:cdc42 GTP-Binding Protein; D020830:rac1 GTP-Binding Protein; D000099221:Protein Kinase C zeta; C489850:ECT2 protein, human; C105295:protease-activated receptor 3