Ankyrin-G Is a Molecular Partner of E-cadherin in Epithelial Cells and Early Embryos

Abstract

E-cadherin is a ubiquitous component of lateral membranes in epithelial tissues and is required to form the first lateral membrane domains in development. Here, we identify ankyrin-G as a molecular partner of E-cadherin and demonstrate that ankyrin-G and ␤-2-spectrin are required for accumulation of E-cadherin at the lateral membrane in both epithelial cells and early embryos. Ankyrin-G binds to the cytoplasmic domain of E-cadherin at a conserved site distinct from that of ␤-catenin. Ankyrin-G also recruits ␤-2-spectrin to E-cadherin-␤-catenin complexes, thus providing a direct connection between E-cadherin and the spectrin/actin skeleton. In addition to restricting the membrane mobility of E-cadherin, ankyrin-G and ␤-2-spectrin also are required for exit of E-cadherin from the trans-Golgi network in a microtubule-dependent pathway. Ankyrin-G and ␤-2-spectrin co-localize with E-cadherin in preimplantation mouse embryos. Moreover, knockdown of either ankyrin-G or ␤-2-spectrin in one cell of a two-cell embryo blocks accumulation of E-cadherin at sites of cell-cell contact. E-cadherin thus requires both ankyrin-G and ␤-2-spectrin for its cellular localization in early embryos as well as cultured epithelial cells. We have recently reported that ankyrin-G and ␤-2-spectrin collaborate in biogenesis of the lateral membrane (

Adducin Promotes Micrometer-Scale Organization of β2-Spectrin in Lateral Membranes of Bronchial Epithelial Cells

“…Loss of ankyrin-G or ␤2-spectrin abolishes de novo formation of lateral membranes during mitosis (Kizhatil and Bennett, 2004;Kizhatil et al, 2007a), whereas loss of adducin has no effect ( Figure 3B). Moreover, cells depleted of either ankyrin-G or ␤2-spectrin accumulate E-cadherin in the transGolgi (Kizhatil et al, 2007b). In contrast, E-cadherin is not reduced at the lateral membrane and does not appear in an intracellular compartment in adducin-depleted cells ( Figure 2).…”

“…Moreover, a mutant E-cadherin with reduced ankyrin-G-binding activity exhibits increased lateral diffusion in HBE cells (Kizhatil et al, 2007b). We therefore evaluated the lateral mobility of E-cadherin in adducin-depleted cells by measuring the FRAP of E-cadherin-GFP.…”

“…Recently, ␤2-spectrin and ankyrin have been demonstrated to be required for both stability and biogenesis of the lateral membrane of cultured epithelial cells (Kizhatil and Bennett, 2004;Kizhatil et al, 2007a). Furthermore, E-cadherin has been shown to bind directly to ankyrin-G and to require ankyrin-G and ␤2-spectrin for transport to the lateral membrane (Kizhatil et al, 2007b). Combined, these early and recent findings highlight the need for a closer examination of additional components of the spectrin-based membrane skeleton within epithelial lateral membranes.…”

Genetic Studies of Spectrin in the Larval Fat Body ofDrosophila melanogaster: Evidence for a Novel Lipid Uptake Apparatus

“…Spectrin and ankyrin are most familiar as components of a subplasma membrane protein scaffold known as the spectrin cytoskeleton (Baines 2010). In one long-standing hypothesis the spectrin cytoskeleton is thought to capture and stabilize interacting membrane proteins as they arrive at the cell surface, creating domains of specialized composition and function (Dubreuil 2006).Recent genetic studies in a number of model systems suggest that spectrin and ankyrin have further roles in intracellular membrane traffic (Kizhatil et al 2007(Kizhatil et al , 2009Ayalon et al 2008;Stabach et al 2008;Clarkson et al 2010;Lorenzo et al 2010;Tjota et al 2011).Given the conservation of spectrin and ankyrin genes between vertebrates and invertebrates, one would expect that their functions should also be conserved. Indeed, as is the case in vertebrates, loss-of-function mutations of a-and b-spectrin and ankyrin2 in Drosophila are lethal early in development (Lee et al 1993;Dubreuil et al 2000;Koch et al 2008;Pielage et al 2008).…”

Evidence of a Structural and Functional Ammonium Transporter RhBG·Anion Exchanger 1·Ankyrin-G Complex in Kidney Epithelial Cells

“…A very recent study showed a physical and functional interaction between kAE1 and Na ϩ ,K ϩ -ATPase in renal ␣-intercalated cells (39), and Na ϩ ,K ϩ -ATPase is known to bind ankyrin-G (26). The renal RhBG⅐kAE1⅐ankyrin-G complex described here, possibly including Na ϩ ,K ϩ -ATPase, is a new evidence of the great diversity of proteins that are organized in membrane microdomains in many cell types, under the control of ankyrins: ankyrin-G for neurofascin, KCNQ2/3, and voltage-gated Na ϩ channel in epithelial cells (40 -44) or E-cadherin and Na ϩ ,K ϩ -ATPase in axon initial segment (33,45) and ankyrin-B for Na ϩ ,K ϩ -ATPase, Na ϩ -Ca 2ϩ exchanger, and inositol triphosphate receptor in cardiomyocytes (46 -48) and ankyrin-R for Rh and eAE1 in RBCs (4,6). However, whereas extracellular epitopes of mutant RhBG-F419A/L420A/D421A are detectable at the surface of HEK293 cells (2), mutant kAE1-delABS is not, although it is partly expressed at plasma membrane.…”