Involvement of LMO7 in the Association of Two Cell-Cell Adhesion Molecules, Nectin and E-cadherin, through Afadin and α-Actinin in Epithelial Cells

Abstract

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 ␣-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 cellcell 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 ␣-actinin, an actin filament-bundling protein, which bound to ␣-catenin. Immunoprecipitation analysis revealed that LMO7 was associated with both the nectin-afadin and E-cadherin-catenin systems. LMO7 was assembled at the cellcell adhesion sites after both the nectin-afadin and Ecadherin-catenin systems had been assembled. These results indicate that LMO7 is an afadin-and ␣-actininbinding protein that connects the nectin-afadin and Ecadherin-catenin systems through ␣-actinin.

Anchoring Junctions As Drug Targets: Role in Contraceptive Development

“…ADIP was also found to localize to the perinuclear region, specifically the Golgi complex, and bind to ␤Ј-COP in vitro and in vivo (Asada et al, 2004), a subunit protein of the coatomer complex involved in protein trafficking events (Schekman and Orci, 1996). The fourth and most recently described type of cross-talk involves LIM domain only 7, an l-afadin and ␣-actinin binding protein that connects the two multiprotein complexes via ␣-actinin (Ooshio et al, 2004). Specifically, LIM domain only 7 associated with both nectin-afadin and cadherin-catenin adhesion complexes by immunoprecipitation (Ooshio et al, 2004) and failed to localize to the desmosome and tight junction by immunofluorescence and immunoelectron microscopy (Ooshio et al, 2004 Kuroda et al, 2002;Takai and Nakanishi, 2003)] were infertile, resulting from malformations in the head and midpiece of elongated spermatids (Mueller et al, 2003;Inagaki et al, 2006).…”

“…The fourth and most recently described type of cross-talk involves LIM domain only 7, an l-afadin and ␣-actinin binding protein that connects the two multiprotein complexes via ␣-actinin (Ooshio et al, 2004). Specifically, LIM domain only 7 associated with both nectin-afadin and cadherin-catenin adhesion complexes by immunoprecipitation (Ooshio et al, 2004) and failed to localize to the desmosome and tight junction by immunofluorescence and immunoelectron microscopy (Ooshio et al, 2004 Kuroda et al, 2002;Takai and Nakanishi, 2003)] were infertile, resulting from malformations in the head and midpiece of elongated spermatids (Mueller et al, 2003;Inagaki et al, 2006). In addition, nectin-like molecule-2 [TSLC1, also known as IGSF4 (Wakayama et al, 2003)], a member of the nectin family of cell adhesion proteins and a germ cell product, was shown to be equally important for spermatogenesis and fertility (Wakayama et al, 2003;Fujita et al, 2006;Surace et al, 2006;Yamada et al, 2006b).…”

The N and C Termini of ZO-1 Are Surrounded by Distinct Proteins and Functional Protein Networks

“…Consistent with this differential tagging, cingulin (22) and actin (21) are known to interact with the C terminus of ZO-1. LMO7 is known to interact at cell junctions with nectin and afadin and to shuttle to the nucleus, where it functions as a transcriptional regulator (44).…”

Knockdown of Lmo7 inhibits chick myogenesis

“…1). The CH domain, at the amino terminal end, is predicted to bind actin, and the PDZ and LIM domains are both protein-protein interaction domains [7,20]. In skeletal muscle, Lmo7 has a role as a transcription factor regulating the expression of many skeletal muscle genes, including Pax3, Pax7, MyoD, and Myf5 [5,9].…”

“…Lmo7 is a multifunctional protein that can be found in the nucleus, cytoplasm and/or at adhesion junctions in many tissues, with high levels of expression in skeletal muscle and heart [20,21]. It is alternatively spliced and contains a predicted calponin homology (CH) Abbreviations DMEM, Dulbecco's modified Eagle's medium; DSHB, Developmental Studies Hybridoma Bank; eGFP, enhanced Green Fluorescent Protein; MbCD, methyl-b-cyclodextrin.…”