scholarly journals Retention of a cell adhesion complex at the paranodal junction requires the cytoplasmic region of Caspr

2002 ◽  
Vol 157 (7) ◽  
pp. 1247-1256 ◽  
Author(s):  
Leora Gollan ◽  
Helena Sabanay ◽  
Sebastian Poliak ◽  
Erik O. Berglund ◽  
Barbara Ranscht ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Cell Adhesion ◽  
Cell Surface ◽  
Cell Adhesion Molecules ◽  
Cytoplasmic Domain ◽  
Short Sequence ◽  
Extracellular Region ◽  
A Cell ◽  
Adhesion Complex ◽  
Protein 4.1B

An axonal complex of cell adhesion molecules consisting of Caspr and contactin has been found to be essential for the generation of the paranodal axo-glial junctions flanking the nodes of Ranvier. Here we report that although the extracellular region of Caspr was sufficient for directing it to the paranodes in transgenic mice, retention of the Caspr–contactin complex at the junction depended on the presence of an intact cytoplasmic domain of Caspr. Using immunoelectron microscopy, we found that a Caspr mutant lacking its intracellular domain was often found within the axon instead of the junctional axolemma. We further show that a short sequence in the cytoplasmic domain of Caspr mediated its binding to the cytoskeleton-associated protein 4.1B. Clustering of contactin on the cell surface induced coclustering of Caspr and immobilized protein 4.1B at the plasma membrane. Furthermore, deletion of the protein 4.1B binding site accelerated the internalization of a Caspr–contactin chimera from the cell surface. These results suggest that Caspr serves as a “transmembrane scaffold” that stabilizes the Caspr/contactin adhesion complex at the paranodal junction by connecting it to cytoskeletal components within the axon.

scholarly journals Replacement of the phospholipid-anchor in the contact site A glycoprotein of D. discoideum by a transmembrane region does not impede cell adhesion but reduces residence time on the cell surface

1994 ◽  
Vol 124 (1) ◽  
pp. 205-215 ◽  
Author(s):  
A Barth ◽  
A Müller-Taubenberger ◽  
P Taranto ◽  
G Gerisch
Keyword(s):  
Plasma Membrane ◽  
Cell Adhesion ◽  
Cell Surface ◽  
Transmembrane Region ◽  
Contact Site ◽  
A Cell ◽  
Internalization Rate ◽  
Actin Promoter ◽  
Wild Type Form

The contact site A (csA) glycoprotein of Dictyostelium discoideum, a cell adhesion molecule expressed in aggregating cells, is inserted into the plasma membrane by a ceramide-based phospholipid (PL) anchor. A carboxyterminal sequence of 25 amino acids of the primary csA translation product proved to contain the signal required for PL modification. CsA is known to be responsible for rapid, EDTA-resistant cohesion of cells in agitated suspensions. To investigate the role of the PL modification of this protein, the anchor was replaced by the transmembrane region and short cytoplasmic tail of another plasma membrane protein of D. discoideum. In cells transformed with appropriate vectors, PL-anchored or transmembrane csA was expressed under the control of an actin promoter during growth and development. The transmembrane form enabled the cells to agglutinate in the presence of shear forces, similar to the PL-anchored wild-type form. However, the transmembrane form was much more rapidly internalized and degraded. In comparison to other cell-surface glycoproteins of D. discoideum the internalization rate of the PL-anchored csA was extremely slow, most likely because of its exclusion from the clathrin-mediated pathway of pinocytosis. Thus, our results indicate that the phospholipid modification is not essential for the csA-mediated fast type of cell adhesion but guarantees long persistence of the protein on the cell surface.

scholarly journals Cytoskeletal-membrane interactions: a stable interaction between cell surface glycoconjugates and doublet microtubules of the photoreceptor connecting cilium.

1987 ◽  
Vol 105 (6) ◽  
pp. 2973-2987 ◽  
Author(s):  
C J Horst ◽  
D M Forestner ◽  
J C Besharse
Keyword(s):  
Plasma Membrane ◽  
Cell Surface ◽  
Molecular Mass ◽  
Lipid Bilayer ◽  
Neonatal Rat ◽  
Sds Page ◽  
A Cell ◽  
The Cross ◽  
Triton X ◽  
Cell Surface Glycoconjugates

The ciliary base is marked by a transition zone in which Y-shaped cross-linkers extend from doublet microtubules to the plasma membrane. Our goal was to investigate the hypothesis that the cross-linkers form a stable interaction between membrane or cell surface components and the underlying microtubule cytoskeleton. We have combined Triton X-100 extraction with lectin cytochemistry in the photoreceptor sensory cilium to investigate the relationship between cell surface glycoconjugates and the underlying cytoskeleton, and to identify the cell surface components involved. Wheat germ agglutinin (WGA) binds heavily to the cell surface in the region of the Y-shaped cross-linkers of the neonatal rat photoreceptor cilium. WGA binding is not removed by prior digestion with neuraminidase and succinyl-WGA also binds the proximal cilium, suggesting a predominance of N-acetylglucosamine containing glycoconjugates. Extraction of the photoreceptor plasma membrane with Triton X-100 removes the lipid bilayer, leaving the Y-shaped crosslinkers associated with the axoneme. WGA-binding sites are found at the distal ends of the crosslinkers after Triton X-100 extraction, indicating that the microtubule-membrane cross-linkers retain both a transmembrane and a cell surface component after removal of the lipid bilayer. To identify glycoconjugate components of the cross-linkers we used a subcellular fraction enriched in axonemes from adult bovine retinas. Isolated, detergent-extracted bovine axonemes show WGA binding at the distal ends of the cross-linkers similar to that seen in the neonatal rat. Proteins of the axoneme fraction were separated by SDS-PAGE and electrophoretically transferred to nitrocellulose. WGA labeling of the nitrocellulose transblots reveals three glycoconjugates, all of molecular mass greater than 400 kD. The major WGA-binding glycoconjugate has an apparent molecular mass of approximately 600 kD and is insensitive to prior digestion with neuraminidase. This glycoconjugate may correspond to the dominant WGA-binding component seen in cytochemical experiments.

scholarly journals Tyrosine Phosphorylation at a Site Highly Conserved in the L1 Family of Cell Adhesion Molecules Abolishes Ankyrin Binding and Increases Lateral Mobility of Neurofascin

1997 ◽  
Vol 137 (3) ◽  
pp. 703-714 ◽  
Author(s):  
Timothy D. Garver ◽  
Qun Ren ◽  
Shmuel Tuvia ◽  
Vann Bennett
Keyword(s):  
Cell Adhesion ◽  
Tyrosine Phosphorylation ◽  
Adhesion Molecules ◽  
Tyrosine Kinases ◽  
Cell Adhesion Molecules ◽  
Protein Tyrosine Kinase ◽  
Neuroblastoma Cells ◽  
Cytoplasmic Domain ◽  
Lateral Mobility

This paper presents evidence that a member of the L1 family of ankyrin-binding cell adhesion molecules is a substrate for protein tyrosine kinase(s) and phosphatase(s), identifies the highly conserved FIGQY tyrosine in the cytoplasmic domain as the principal site of phosphorylation, and demonstrates that phosphorylation of the FIGQY tyrosine abolishes ankyrin-binding activity. Neurofascin expressed in neuroblastoma cells is subject to tyrosine phosphorylation after activation of tyrosine kinases by NGF or bFGF or inactivation of tyrosine phosphatases with vanadate or dephostatin. Furthermore, both neurofascin and the related molecule Nr-CAM are tyrosine phosphorylated in a developmentally regulated pattern in rat brain. The FIGQY sequence is present in the cytoplasmic domains of all members of the L1 family of neural cell adhesion molecules. Phosphorylation of the FIGQY tyrosine abolishes ankyrin binding, as determined by coimmunoprecipitation of endogenous ankyrin and in vitro ankyrin-binding assays. Measurements of fluorescence recovery after photobleaching demonstrate that phosphorylation of the FIGQY tyrosine also increases lateral mobility of neurofascin expressed in neuroblastoma cells to the same extent as removal of the cytoplasmic domain. Ankyrin binding, therefore, appears to regulate the dynamic behavior of neurofascin and is the target for regulation by tyrosine phosphorylation in response to external signals. These findings suggest that tyrosine phosphorylation at the FIGQY site represents a highly conserved mechanism, used by the entire class of L1-related cell adhesion molecules, for regulation of ankyrin-dependent connections to the spectrin skeleton.

scholarly journals Identification of novel cell-adhesion molecules in peripheral nerves using a signal-sequence trap

2005 ◽  
Vol 2 (1) ◽  
pp. 27-38 ◽  
Author(s):  
IVO SPIEGEL ◽  
KONSTANTIN ADAMSKY ◽  
MENAHEM EISENBACH ◽  
YAEL ESHED ◽  
ADRIAN SPIEGEL ◽  
...  
Keyword(s):  
Cell Adhesion ◽  
Sciatic Nerve ◽  
Cell Surface ◽  
Adhesion Molecules ◽  
Schwann Cells ◽  
Cell Adhesion Molecules ◽  
Signal Sequence ◽  
Cdna Libraries ◽  
Rat Sciatic Nerve ◽  
Myelinated Nerves

The development and maintenance of myelinated nerves in the PNS requires constant and reciprocal communication between Schwann cells and their associated axons. However, little is known about the nature of the cell-surface molecules that mediate axon–glial interactions at the onset of myelination and during maintenance of the myelin sheath in the adult. Based on the rationale that such molecules contain a signal sequence in order to be presented on the cell surface, we have employed a eukaryotic-based, signal-sequence-trap approach to identify novel secreted and membrane-bound molecules that are expressed in myelinating and non-myelinating Schwann cells. Using cDNA libraries derived from dbcAMP-stimulated primary Schwann cells and 3-day-old rat sciatic nerve mRNAs, we generated an extensive list of novel molecules expressed in myelinating nerves in the PNS. Many of the identified proteins are cell-adhesion molecules (CAMs) and extracellular matrix (ECM) components, most of which have not been described previously in Schwann cells. In addition, we have identified several signaling receptors, growth and differentiation factors, ecto-enzymes and proteins that are associated with the endoplasmic reticulum and the Golgi network. We further examined the expression of several of the novel molecules in Schwann cells in culture and in rat sciatic nerve by primer-specific, real-time PCR and in situ hybridization. Our results indicate that myelinating Schwann cells express a battery of novel CAMs that might mediate their interactions with the underlying axons.

scholarly journals Ankyrin-binding proteins related to nervous system cell adhesion molecules: candidates to provide transmembrane and intercellular connections in adult brain.

1993 ◽  
Vol 121 (1) ◽  
pp. 121-133 ◽  
Author(s):  
J Q Davis ◽  
T McLaughlin ◽  
V Bennett
Keyword(s):  
Nervous System ◽  
Cell Adhesion ◽  
Amino Acid ◽  
Amino Acid Sequence ◽  
Binding Site ◽  
Adhesion Molecules ◽  
Cell Adhesion Molecules ◽  
Binding Proteins ◽  
Cytoplasmic Domain ◽  
System Cell

A major class of ankyrin-binding glycoproteins have been identified in adult rat brain of 186, 155, and 140 kD that are alternatively spliced products of the same pre-mRNA. Characterization of cDNAs demonstrated that ankyrin-binding glycoproteins (ABGPs) share 72% amino acid sequence identity with chicken neurofascin, a membrane-spanning neural cell adhesion molecule in the Ig super-family expressed in embryonic brain. ABGP polypeptides have the following features consistent with a role as ankyrin-binding proteins in vitro and in vivo: (a) ABGPs and ankyrin associate as pure proteins in a 1:1 molar stoichiometry; (b) the ankyrin-binding site is located in the COOH-terminal 21 kD of ABGP186 which contains the predicted cytoplasmic domain; (c) ABGP186 is expressed at approximately the same levels as ankyrin (15 pmoles/milligram of membrane protein); and (d) ABGP polypeptides are co-expressed with the adult form of ankyrinB late in postnatal development and are colocalized with ankyrinB by immunofluorescence. Similarity in amino acid sequence and conservation of sites of alternative splicing indicate that genes encoding ABGPs and neurofascin share a common ancestor. However, the major differences in developmental expression reported for neurofascin in embryos versus the late postnatal expression of ABGPs suggest that ABGPs and neurofascin represent products of gene duplication events that have subsequently evolved in parallel with distinct roles. The predicted cytoplasmic domains of rat ABGPs and chicken neurofascin are nearly identical to each other and closely related to a group of nervous system cell adhesion molecules with variable extracellular domains, which includes L1, Nr-CAM, and Ng-CAM of vertebrates, and neuroglian of Drosophila. The ankyrin-binding site of rat ABGPs is localized to the C-terminal 200 residues which encompass the cytoplasmic domain, suggesting the hypothesis that ability to associate with ankyrin may be a shared feature of neurofascin and related nervous system cell adhesion molecules.

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