Structure of the chicken neuron-glia cell adhesion molecule, Ng-CAM: origin of the polypeptides and relation to the Ig superfamily.

Abstract

The neuron-glia cell adhesion molecule (Ng-CAM) mediates both neuron-neuron and neuron-glia adhesion; it is detected on SDS-PAGE as a predominant 135-kD glycoprotein, with minor components of 80, 190, and 210 kD. We have isolated cDNA clones encoding the entire sequence of chicken Ng-CAM. The predicted extracellular region includes six immunoglobulin-like domains followed by five fibronectin-type III repeats, structural features that are characteristic of several neural CAMs of the N-CAM superfamily. The amino acid sequence of chicken Ng-CAM is most similar to that of mouse L1 but the overall identity is only 40% and Ng-CAM contains a short fibronectin-like segment with an RGD sequence that has no counterpart in L1. These findings suggest that Ng-CAM and L1 may not be equivalent molecules in chicken and mouse. The amino-terminal sequences of the 210-, 190-, and 135-kD components of Ng-CAM are all the same as the predicted amino terminus of the molecule, whereas the 80-kD component begins within the third fibronectin repeat. The cDNA sequence is continuous across the junction between the 135- and 80-kD components, and a single 170-kD Ng-CAM polypeptide was isolated from tunicamycin-treated cells. In addition, all cDNA probes hybridized on Northern blots to a 6-kb RNA, and most hybridized to single bands on Southern blots. These results indicate that the Ng-CAM components are derived from a single polypeptide encoded by a single gene, and that the 135- and 80-kD components are generated from the 210/190-kD species by proteolytic cleavage. The 135-kD component contains most of the extracellular region including all of the immunoglobulin-like domains. It has no transmembrane segment, but it is tightly associated with the membrane. The 80-kD component contains two and a half type III repeats plus the RGD-containing segment, as well as the single transmembrane and cytoplasmic domains. These structural features of Ng-CAM provide a framework for understanding its multiple functions in neuron-neuron interactions, neurite fasciculation, and neuron-glia interactions.

• Authors: M P Burgoon, M Grumet, V Mauro, G M Edelman, B A Cunningham
• Journal: The Journal of cell biology (J Cell Biol) Vol. 112 Issue 5 Pg. 1017-29 (Mar 1991) ISSN: 0021-9525 [Print] United States
• PMID: 1705558 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Cell Adhesion Molecules, Neuronal
• Extracellular Matrix Proteins
• Fibronectins
• Immunoglobulins
• Tenascin

Topics

• Amino Acid Sequence
• Animals
• Base Sequence
• Blotting, Northern
• Blotting, Southern
• Cell Adhesion Molecules, Neuronal (chemistry, genetics)
• Chickens
• Cloning, Molecular
• Extracellular Matrix Proteins (chemistry, genetics)
• Fibronectins (chemistry)
• Genes
• Immunoglobulins (chemistry, genetics)
• Molecular Sequence Data
• Multigene Family
• Repetitive Sequences, Nucleic Acid
• Sequence Homology, Nucleic Acid
• Tenascin