Involvement of LMO7 in the association of two cell-cell adhesion molecules, nectin and E-cadherin, through afadin and alpha-actinin in epithelial cells.
Nectins are Ca(2+)-independent immunoglobulin-like cell-cell adhesion molecules that are involved in formation of cadherin-based adherens junctions (AJs). The nectin-based cell-cell adhesion induces activation of Cdc42 and Rac small G proteins, which eventually enhances the formation of AJs through reorganization of the actin cytoskeleton. Although evidence has accumulated that nectins recruit cadherins to the nectin-based cell-cell adhesion sites through their cytoplasm-associated proteins, afadin and catenins, it is not fully understood how nectins are physically associated with cadherins. Here we identified a rat counterpart of the human LIM domain only 7 (LMO7) as an afadin- and alpha-actinin-binding protein. Rat LMO7 has two splice variants, LMO7a and LMO7b, consisting of 1,729 and 1,395 amino acids, respectively. LMO7 has calponin homology, PDZ, and LIM domains. Western blotting revealed that LMO7 was expressed ubiquitously in various rat tissues. Immunofluorescence and immunoelectron microscopy revealed that LMO7 localized at cell-cell AJs, where afadin localized, in epithelial cells of rat gallbladder. In addition, LMO7 localized at the cytoplasmic faces of apical membranes in the same epithelial cells. We furthermore revealed that LMO7 bound alpha-actinin, an actin filament-bundling protein, which bound to alpha-catenin. Immunoprecipitation analysis revealed that LMO7 was associated with both the nectin-afadin and E-cadherin-catenin systems. LMO7 was assembled at the cell-cell adhesion sites after both the nectin-afadin and E-cadherin-catenin systems had been assembled. These results indicate that LMO7 is an afadin- and alpha-actinin-binding protein that connects the nectin-afadin and E-cadherin-catenin systems through alpha-actinin.
Ooshio
Takako
T
Department of Molecular Biology and Biochemistry, Osaka University Graduate School of Medicine/Faculty of Medicine, 2-2 Yamada-oka Suita, Osaka 565-0871, USA.
Irie
Kenji
K
Morimoto
Koji
K
Fukuhara
Atsunori
A
Imai
Toshio
T
Takai
Yoshimi
Y
D000185:Actinin / Q000235:genetics / Q000378:metabolism*; D022005:Adherens Junctions / Q000378:metabolism; D000818:Animals; D015820:Cadherins / Q000235:genetics / Q000378:metabolism*; D002448:Cell Adhesion / Q000502:physiology; D015815:Cell Adhesion Molecules / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D003598:Cytoskeletal Proteins / Q000378:metabolism; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D016547:Kinesins; D060588:LIM Domain Proteins; D051379:Mice; D008840:Microfilament Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D009218:Myosins; D000075983:Nectins; D011485:Protein Binding; D051381:Rats; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D014018:Tissue Distribution; D015534:Trans-Activators / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D020798:Two-Hybrid System Techniques; D051178:alpha Catenin; D051176:beta Catenin
C095516:AFDN protein, human; C490657:Afdn protein, mouse; C495273:CTNNA1 protein, human; C495270:CTNNB1 protein, human; C495267:CTNNB1 protein, mouse; D015820:Cadherins; D015815:Cell Adhesion Molecules; C495272:Ctnna1 protein, mouse; C495268:Ctnnb1 protein, rat; D003598:Cytoskeletal Proteins; D018398:Homeodomain Proteins; D060588:LIM Domain Proteins; C116184:LMO7 protein, human; C490020:LMO7 protein, rat; C485492:Lmo7 protein, mouse; D008840:Microfilament Proteins; D000075983:Nectins; D011994:Recombinant Proteins; D015534:Trans-Activators; D014157:Transcription Factors; C108835:afadin; D051178:alpha Catenin; D051176:beta Catenin; D000185:Actinin; D009218:Myosins; D016547:Kinesins