Role of fibronectin in the inhibitory effect of TGF-β on choline acetyltransferase activity in co-cultures of spinal cord neurons and myotubes

Abstract

We have recently shown that the enhanced expression of choline acetyltransferase (ChAT) activity in co-cultures of spinal cord motoneurons and muscle cells was blocked by transforming growth factor-β (TGF-β) ( Dev. Brain Res., 57, 129–137, 1990). This study was performed to investigate the role of fibronectin in this effect. TGF-β increased fibronectin level about 2-fold in extracellular matrix of spinal cord cells and skeletal myotubes in culture. Addition of a synthetic polypeptide that competitively inhibits fibronectin binding to its cell surface receptor recovered the TGF-β-induced suppression of ChAT activity in co-cultures. The polypeptide did not affect ChAT activity in cultures of spinal cord cells alone or in co-cultures without TGF-β. These results indicate that TGF-β inhibits the stimulation of ChAT activity in spinal cord neurons in co-culture through a change in the composition and/or amount of fibronectin in the extracellular matrix at neuromuscular contacts.