Glial cells express N-CAM/D2-CAM-like polypeptides in vitro

Abstract

The joining together of neurites to form fascicles and the growth of axons along glial surfaces during early development suggest that neurone-neurone and neurone-glial adhesion interactions are of considerable importance for defining nerve tracts. In vitro studies have indicated that adhesion between neurones involves a glycoprotein that has been independently studied under the names of N-CAM (for neural cell adhesion molecule), D2-CAM and BSP-2 (refs 10, 11). As N-CAM/D2-CAM appears to be a homophilic ligand that binds to N-CAM/D2-CAM polypeptide on adjacent cells, this glycoprotein is potentially important in adhesion interactions between any two N-CAM/D2-CAM-expressing cells. While it has been suggested that neurone-glial adhesion involves molecules other than N-CAM/D2-CAM, it is known that N-CAM/D2-CAM antigenic determinants are expressed by glial cells in vivo and that injection of anti-N-CAM antibodies into the eye-cup of chick embryos disrupts normal patterns of neuritic apposition to glial endfeet in the developing optic stalk. Do the molecules expressed by glia share restricted antigenic determinants, or binding domains, with N-CAM/D2-CAM, or are N-CAM/D2-CAM polypeptides expressed by glia? Here we present immunocytochemical evidence which suggests that all classes of macroglia express N-CAM/D2-CAM antigenic determinants on their surfaces and immunochemical analyses which indicate that the molecules expressed by purified astrocytes are closely similar, or identical, to at least some forms of N-CAM/D2-CAM obtained from whole brain or purified neurones. However, our results also suggest that different N-CAM/D2-CAM polypeptides may be separately expressed by neurones and astrocytes.

A heparin-binding domain from N-CAM is involved in neural cell-substratum adhesion.

“…N-CAM has been previously shown to mediate neuron-neuron (33) and neuron-muscle (11) adhesion, and recently has been shown to be present on glial cells (18,20) and to participate in neuron-glia cell adhesion (18). Our data indicate that N-CAM contains a heparinbinding domain that is required for cell attachment to retinal cell extracellular matrix material.…”

“…In light of the evidence that neurite outgrowth can be promoted by heparin-binding domains of extracellular matrix molecules (8,24), it is promising to speculate that glial endfeet contain a subset of N-CAM molecules that possess a heparin-binding domain. Recent studies in several laboratories suggest that distinct subsets of N-CAM are present on different classes of cells in the nervous system (18,20,35). Immunocytochemical staining of developing nervous tissue with the BIA3 MAb could provide information regarding whether this MAb recognizes a subset of N-CAM.…”

Characterization of the kinetics of neural cell adhesion molecule homophilic binding

“…The neural cell adhesion molecule (NCAM; for review see [1,2]) is currently the most extensively characterized of these. It is expressed on all major neural cell types in the central and peripheral nervous systems [3][4][5]. It mediates aggregation of single cells [6] and histotypic deployment in neural tissue culture [7].…”

Endocrine cells share expression of N‐CAM with neurones

“…While N-CAM was originally considered to be limited to neurones in adult tissues, ultrastructural immunocytochemical studies have since provided unequivocal evidence that glial cells, both astrocytes [6,10] and Schwann cells [ 111, also express N-CAM (see also [ 12,131). Apart from a very limited expression by skeletal muscle at the neuromuscular junction [14], its expression in the adult …”