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LAD-1, the Caenorhabditis elegans L1CAM homologue, participates in embryonic and gonadal morphogenesis and is a substrate for fibroblast growth factor receptor pathway-dependent phosphotyrosine-based signaling.

Chen L, Ong B, Bennett V - J. Cell Biol. (2001)

Bottom Line: In addition, the ubiquitously expressed LAD-1, which binds to ankyrin-G, colocalizes with the C. elegans ankyrin, UNC-44, in multiple tissues at sites of cell-cell contact.These findings suggest a novel ankyrin-independent role for LAD-1 related to FGFR signaling.Taken together, these results indicate that L1CAMs constitute a family of ubiquitous adhesion molecules, which participate in tissue morphogenesis and maintaining tissue integrity in metazoans.

View Article: PubMed Central - PubMed

Affiliation: Howard Hughes Medical Institute, Department of Cell Biology, and Department of Biochemistry, Duke University Medical Center, Durham, NC 27710, USA. l.chen@cellbio.duke.edu

ABSTRACT
This study shows that L1-like adhesion (LAD-1), the sole Caenorhabditis elegans homologue of the L1 family of neuronal adhesion molecules, is required for proper development of the germline and the early embryo and embryonic and gonadal morphogenesis. In addition, the ubiquitously expressed LAD-1, which binds to ankyrin-G, colocalizes with the C. elegans ankyrin, UNC-44, in multiple tissues at sites of cell-cell contact. Finally, we show that LAD-1 is phosphorylated in a fibroblast growth factor receptor (FGFR) pathway-dependent manner on a tyrosine residue in the highly conserved ankyrin-binding motif, FIGQY, which was shown previously to abolish the L1 family of cell adhesion molecule (L1CAM) binding to ankyrin in cultured cells. Immunofluorescence studies revealed that FIGQY-tyrosine-phosphorylated LAD-1 does not colocalize with nonphosphorylated LAD-1 or UNC-44 ankyrin but instead is localized to sites that undergo mechanical stress in polarized epithelia and axon-body wall muscle junctions. These findings suggest a novel ankyrin-independent role for LAD-1 related to FGFR signaling. Taken together, these results indicate that L1CAMs constitute a family of ubiquitous adhesion molecules, which participate in tissue morphogenesis and maintaining tissue integrity in metazoans.

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The LAD-1 cytoplasmic tail binds and recruits mammalian ankyrin to the plasma membrane in cultured cells and similar to LAD-1 UNC-44 ankyrin is localized to the plasma membrane at sites of cell–cell contact in multiple tissues in C. elegans. (A) Cytoplasmic localization of exogenous ankyrin in human embryonic kidney 293 cells transfected with murine GFP-tagged ankyrinG (Zhang et al., 1998). Upon cotransfection with a neurofascin–LAD-1 cytoplasmic tail chimera, cytoplasmic ankyrinG (green) is recruited to the plasma membrane, colocalizing with the L1CAM chimera (B, red). Immunofluorescence labeling of UNC-44 in multiple tissues in embryos as shown in C and D. The long arrows in C point to cytoplasmic ankyrin in the intestinal primordium. No unc-44 ankyrin expression is evident in early embryos as indicated by the short arrow, which shows a 12-cell staged embryo. The arrows in D and E point to strong unc-44 ankyrin expression in the nerve ring in the embryo and adult, respectively. In the adult (F), UNC-44 ankyrin is detected in the pharynx (short arrow), body wall muscles (small arrowhead), body wall muscle sarcomeres (large arrowhead), and commissural axons (long arrow). Bars: (A and B) 5 μm; (C and D) 10 μm; (E and F) 50 μm.
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fig3: The LAD-1 cytoplasmic tail binds and recruits mammalian ankyrin to the plasma membrane in cultured cells and similar to LAD-1 UNC-44 ankyrin is localized to the plasma membrane at sites of cell–cell contact in multiple tissues in C. elegans. (A) Cytoplasmic localization of exogenous ankyrin in human embryonic kidney 293 cells transfected with murine GFP-tagged ankyrinG (Zhang et al., 1998). Upon cotransfection with a neurofascin–LAD-1 cytoplasmic tail chimera, cytoplasmic ankyrinG (green) is recruited to the plasma membrane, colocalizing with the L1CAM chimera (B, red). Immunofluorescence labeling of UNC-44 in multiple tissues in embryos as shown in C and D. The long arrows in C point to cytoplasmic ankyrin in the intestinal primordium. No unc-44 ankyrin expression is evident in early embryos as indicated by the short arrow, which shows a 12-cell staged embryo. The arrows in D and E point to strong unc-44 ankyrin expression in the nerve ring in the embryo and adult, respectively. In the adult (F), UNC-44 ankyrin is detected in the pharynx (short arrow), body wall muscles (small arrowhead), body wall muscle sarcomeres (large arrowhead), and commissural axons (long arrow). Bars: (A and B) 5 μm; (C and D) 10 μm; (E and F) 50 μm.

Mentions: L1CAMs interact with ankyrins via the FIGQY ankyrin-binding motif located in their cytoplasmic tails (Garver et al., 1997; Zhang et al., 1998), which is also present in LAD-1. To determine if LAD-1 binds ankyrin, we performed a binding/recruitment assay using human embryonic kidney 293 cell cultures (Fig. 3, A and B) as described (Zhang et al., 1998). Green fluorescent protein (GFP)–tagged 270 kD rat ankyrinG transfected into 293 cells was primarily localized in the cytoplasm (Fig. 3 A) (Zhang et al., 1998). Upon cotransfection with a chimera construct comprised of the LAD-1 cytoplasmic tail fused to the entire rat neurofascin extracellular and transmembrane domains, the cytoplasmic ankyrinG–GFP redistributed to the plasma membrane, colocalizing with the neurofascin–LAD-1 chimeric protein (Fig. 3 B). This result showed that the LAD-1 cytoplasmic tail could bind and recruit cytoplasmic mammalian ankyrin to the plasma membrane.


LAD-1, the Caenorhabditis elegans L1CAM homologue, participates in embryonic and gonadal morphogenesis and is a substrate for fibroblast growth factor receptor pathway-dependent phosphotyrosine-based signaling.

Chen L, Ong B, Bennett V - J. Cell Biol. (2001)

The LAD-1 cytoplasmic tail binds and recruits mammalian ankyrin to the plasma membrane in cultured cells and similar to LAD-1 UNC-44 ankyrin is localized to the plasma membrane at sites of cell–cell contact in multiple tissues in C. elegans. (A) Cytoplasmic localization of exogenous ankyrin in human embryonic kidney 293 cells transfected with murine GFP-tagged ankyrinG (Zhang et al., 1998). Upon cotransfection with a neurofascin–LAD-1 cytoplasmic tail chimera, cytoplasmic ankyrinG (green) is recruited to the plasma membrane, colocalizing with the L1CAM chimera (B, red). Immunofluorescence labeling of UNC-44 in multiple tissues in embryos as shown in C and D. The long arrows in C point to cytoplasmic ankyrin in the intestinal primordium. No unc-44 ankyrin expression is evident in early embryos as indicated by the short arrow, which shows a 12-cell staged embryo. The arrows in D and E point to strong unc-44 ankyrin expression in the nerve ring in the embryo and adult, respectively. In the adult (F), UNC-44 ankyrin is detected in the pharynx (short arrow), body wall muscles (small arrowhead), body wall muscle sarcomeres (large arrowhead), and commissural axons (long arrow). Bars: (A and B) 5 μm; (C and D) 10 μm; (E and F) 50 μm.
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Related In: Results  -  Collection

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fig3: The LAD-1 cytoplasmic tail binds and recruits mammalian ankyrin to the plasma membrane in cultured cells and similar to LAD-1 UNC-44 ankyrin is localized to the plasma membrane at sites of cell–cell contact in multiple tissues in C. elegans. (A) Cytoplasmic localization of exogenous ankyrin in human embryonic kidney 293 cells transfected with murine GFP-tagged ankyrinG (Zhang et al., 1998). Upon cotransfection with a neurofascin–LAD-1 cytoplasmic tail chimera, cytoplasmic ankyrinG (green) is recruited to the plasma membrane, colocalizing with the L1CAM chimera (B, red). Immunofluorescence labeling of UNC-44 in multiple tissues in embryos as shown in C and D. The long arrows in C point to cytoplasmic ankyrin in the intestinal primordium. No unc-44 ankyrin expression is evident in early embryos as indicated by the short arrow, which shows a 12-cell staged embryo. The arrows in D and E point to strong unc-44 ankyrin expression in the nerve ring in the embryo and adult, respectively. In the adult (F), UNC-44 ankyrin is detected in the pharynx (short arrow), body wall muscles (small arrowhead), body wall muscle sarcomeres (large arrowhead), and commissural axons (long arrow). Bars: (A and B) 5 μm; (C and D) 10 μm; (E and F) 50 μm.
Mentions: L1CAMs interact with ankyrins via the FIGQY ankyrin-binding motif located in their cytoplasmic tails (Garver et al., 1997; Zhang et al., 1998), which is also present in LAD-1. To determine if LAD-1 binds ankyrin, we performed a binding/recruitment assay using human embryonic kidney 293 cell cultures (Fig. 3, A and B) as described (Zhang et al., 1998). Green fluorescent protein (GFP)–tagged 270 kD rat ankyrinG transfected into 293 cells was primarily localized in the cytoplasm (Fig. 3 A) (Zhang et al., 1998). Upon cotransfection with a chimera construct comprised of the LAD-1 cytoplasmic tail fused to the entire rat neurofascin extracellular and transmembrane domains, the cytoplasmic ankyrinG–GFP redistributed to the plasma membrane, colocalizing with the neurofascin–LAD-1 chimeric protein (Fig. 3 B). This result showed that the LAD-1 cytoplasmic tail could bind and recruit cytoplasmic mammalian ankyrin to the plasma membrane.

Bottom Line: In addition, the ubiquitously expressed LAD-1, which binds to ankyrin-G, colocalizes with the C. elegans ankyrin, UNC-44, in multiple tissues at sites of cell-cell contact.These findings suggest a novel ankyrin-independent role for LAD-1 related to FGFR signaling.Taken together, these results indicate that L1CAMs constitute a family of ubiquitous adhesion molecules, which participate in tissue morphogenesis and maintaining tissue integrity in metazoans.

View Article: PubMed Central - PubMed

Affiliation: Howard Hughes Medical Institute, Department of Cell Biology, and Department of Biochemistry, Duke University Medical Center, Durham, NC 27710, USA. l.chen@cellbio.duke.edu

ABSTRACT
This study shows that L1-like adhesion (LAD-1), the sole Caenorhabditis elegans homologue of the L1 family of neuronal adhesion molecules, is required for proper development of the germline and the early embryo and embryonic and gonadal morphogenesis. In addition, the ubiquitously expressed LAD-1, which binds to ankyrin-G, colocalizes with the C. elegans ankyrin, UNC-44, in multiple tissues at sites of cell-cell contact. Finally, we show that LAD-1 is phosphorylated in a fibroblast growth factor receptor (FGFR) pathway-dependent manner on a tyrosine residue in the highly conserved ankyrin-binding motif, FIGQY, which was shown previously to abolish the L1 family of cell adhesion molecule (L1CAM) binding to ankyrin in cultured cells. Immunofluorescence studies revealed that FIGQY-tyrosine-phosphorylated LAD-1 does not colocalize with nonphosphorylated LAD-1 or UNC-44 ankyrin but instead is localized to sites that undergo mechanical stress in polarized epithelia and axon-body wall muscle junctions. These findings suggest a novel ankyrin-independent role for LAD-1 related to FGFR signaling. Taken together, these results indicate that L1CAMs constitute a family of ubiquitous adhesion molecules, which participate in tissue morphogenesis and maintaining tissue integrity in metazoans.

Show MeSH
Related in: MedlinePlus