INSULIN-LIKE GROWTH-FACTOR BINDING PROTEIN-1 AT MOUSE NEUROMUSCULAR SYNAPSES

The insulin-like growth factor (IGF) signaling system includes the gro wth factors and their cell surface receptors, along with circulating I GF binding proteins (IGFBPs) that may alter and modulate the action of these neurotrophic hormones. These IGFBPs, along with IGFs and recept ors, have been detected in various tissues including the brain. In thi s study, using polyclonal antibody to human IGFBP-1 or bovine IGFBP-8, we found that mouse muscle extracts contain similar-sized proteins th at crossreact with these antibodies on Western immunoblots. After esta blishing that these antibodies reacted with the homologous murine IGFB Ps, we performed immunocytochemistry to demonstrate the localization o f IGFBP-1 at the neuromuscular junction, a model nicotinic, cholinergi c synapse, as well as within intramuscular nerves. IGFBP-8, a distinct macromolecule, is present on the surface of muscle fibers and is not present within synapses or nerves. (C) 1994 Wiley-Liss, Inc.