Nerve growth factor modulates myelin-associated glycoprotein binding to sensory neurons

Myelin-associated glycoprotein (MAG) is a molecule expressed by myelinating cells at the myelin/axon interface, which binds to an as yet unidentified molecule on neurons. We have used a MAG-immunoglobulin Fc fusion protein to examine the expression and regulation of the MAG binding molecule on sensory neurons in culture. Binding of the MAG-Fc reached a maximum at 24-48 h and was higher on neurons which expressed high levels of neurofilament. Nerve growth factor (NGF) upregulated expression of the MAG binding molecule in a dose dependent manner. Schwann cells co-cultured with sensory neurons in serum-free medium stimulated maximal expression of the MAG binding molecule, which was decreased by addition of anti-NGF to the co-cultures. This indicated that Schwann cells can modulate expression of the MAG binding molecule via production of NGF and may represent a physiological mechanism for regulation of MAG-MAG binding molecule interactions during myelination and remyelination.