ARIA - A NEUROMUSCULAR-JUNCTION NEUREGULIN

Motor neurons influence the expression and the distribution of acetylc holine receptors in skeletal muscle. Molecules that mediate this caref ully choreographed interaction have recently been identified. One of t hem, ARIA, is a polypeptide purified from chicken brain on the basis o f its ability to stimulate the synthesis of muscle acetylcholine recep tors. The predicted amino acid sequence suggests that ARIA is synthesi zed as a transmembrane precursor protein and that it is a member of a family of ligands that activate receptor tyrosine kinases related to t he epidermal growth factor receptor. Certain features of the ligand fa mily (the neuregulins) and their receptors (erbBs) are reviewed. Evide nce that ARIA plays an important role at developing and mature neuromu scular junctions is discussed.