An atypical PKC directly associates and colocalizes at the epithelial tight junction with ASIP, a mammalian homologue of Caenorhabditis elegans polarity protein PAR-3.
Cell polarity is fundamental to differentiation and function of most cells. Studies in mammalian epithelial cells have revealed that the establishment and maintenance of cell polarity depends upon cell adhesion, signaling networks, the cytoskeleton, and protein transport. Atypical protein kinase C (PKC) isotypes PKCzeta and PKClambda have been implicated in signaling through lipid metabolites including phosphatidylinositol 3-phosphates, but their physiological role remains elusive. In the present study we report the identification of a protein, ASIP (atypical PKC isotype-specific interacting protein), that binds to aPKCs, and show that it colocalizes with PKClambda to the cell junctional complex in cultured epithelial MDCKII cells and rat intestinal epithelia. In addition, immunoelectron microscopy revealed that ASIP localizes to tight junctions in intestinal epithelial cells. Furthermore, ASIP shows significant sequence similarity to Caenorhabditis elegans PAR-3. PAR-3 protein is localized to the anterior periphery of the one-cell embryo, and is required for the establishment of cell polarity in early embryos. ASIP and PAR-3 share three PDZ domains, and can both bind to aPKCs. Taken together, our results suggest a role for a protein complex containing ASIP and aPKC in the establishment and/or maintenance of epithelial cell polarity. The evolutionary conservation of the protein complex and its asymmetric distribution in polarized cells from worm embryo to mammalian-differentiated cells may mean that the complex functions generally in the organization of cellular asymmetry.
Department of Molecular Biology, Yokohama City University School of Medicine, Yokohama 236-0004, Japan.
Y
Y
Izumi
T
T
Hirose
Y
Y
Tamai
S
S
Hirai
Y
Y
Nagashima
T
T
Fujimoto
Y
Y
Tabuse
K J
KJ
Kemphues
S
S
Ohno
D016475:3T3 Cells; D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D000818:Animals; D017173:Caenorhabditis elegans / Q000502:physiology; D029742:Caenorhabditis elegans Proteins; D002352:Carrier Proteins; D015815:Cell Adhesion Molecules; D018797:Cell Cycle Proteins; D002460:Cell Line; D016764:Cell Polarity / Q000502:physiology*; D004285:Dogs; D004847:Epithelial Cells / Q000502:physiology* / Q000648:ultrastructure; D015801:Helminth Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D007413:Intestinal Mucosa / Q000502:physiology* / Q000648:ultrastructure; D007527:Isoenzymes; D008322:Mammals; D051379:Mice; D008969:Molecular Sequence Data; D011493:Protein Kinase C / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D019108:Tight Junctions / Q000502:physiology* / Q000648:ultrastructure; D014158:Transcription, Genetic; D014162:Transfection; D000099293:Protein Kinase C-lambda; D000099221:Protein Kinase C zeta
D048868:Adaptor Proteins, Signal Transducing; D029742:Caenorhabditis elegans Proteins; D002352:Carrier Proteins; D015815:Cell Adhesion Molecules; D018797:Cell Cycle Proteins; D015801:Helminth Proteins; D007527:Isoenzymes; D011493:Protein Kinase C; D017346:Protein Serine-Threonine Kinases; D012333:RNA, Messenger; D011994:Recombinant Proteins; D000099293:Protein Kinase C-lambda; D000099221:Protein Kinase C zeta; C115084:Pard3 protein, mouse; C097238:PAR-3 protein, C elegans