The fibronectin domains of the neural adhesion molecule TAX-1 are necessary and sufficient for homophilic binding.
Cell adhesion molecules belonging to the immunoglobulin superfamily promote cell aggregation and neurite outgrowth. These proteins are multidomain molecules comprising a number of distinct modules, notably Ig domains of the C2 class and fibronectin type III repeats. A subgroup of these neural adhesion molecules are linked to the membrane with a glycosylphosphatidylinositol anchor and show a more restricted pattern of expression in the embryo. Among them, the human homologue of the transient axonal glycoprotein, named TAX-1, shares a great degree of similarity at the protein level with rodent TAG-1. In the present study we set out to determine which domains of TAX-1 are involved in promoting the homophilic, adhesive properties of the molecule. We established stable Schneider-2 cell lines expressing the intact molecule, the fibronectin, or the immunoglobulin domains. The fibronectin domains were necessary and sufficient to mediate homophilic binding and induce cell aggregation, a response also observed with cells expressing the intact TAX-1 molecule. Aggregation was inhibited by the secreted form of the TAG-1 protein. On the other hand, the immunoglobulin domains by themselves were not able to induce cell aggregation. In addition, TAX-1 was localized in areas of cell contact among aggregating cells, justifying its role as an adhesion molecule.
Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology, Heraklion 71110, Crete, Greece. karagogeos@nefeli.imbb.forth.gr
P C
PC
Tsiotra
K
K
Theodorakis
J
J
Papamatheakis
D
D
Karagogeos
D015816:Cell Adhesion Molecules, Neuronal / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D058969:Contactin 2; D018076:DNA, Complementary; D005353:Fibronectins / Q000378:metabolism*; D006133:Growth Substances / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007136:Immunoglobulins / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism; D011485:Protein Binding
C548674:CNTN2 protein, human; D015816:Cell Adhesion Molecules, Neuronal; D058969:Contactin 2; D018076:DNA, Complementary; D005353:Fibronectins; D006133:Growth Substances; D007136:Immunoglobulins; D008562:Membrane Glycoproteins; D010727:Phosphoric Diester Hydrolases; D043265:Phosphatidylinositol Diacylglycerol-Lyase