Diverse functions of the extracellular matrix molecule agrin

The extracellular matrix is a well organized structure with profound effects on the development and the integrity of adherent tissues. Agrin is a component of many matrices, such as the basement membrane of kidney, blood capillaries and the muscle fiber basal lamina, where it is highly concentrated at the neuromuscular junction. During synapse formation agrin is believed to promote differentiation of the postsynaptic muscle fibers and the presynaptic motor neuron. This complex process is, at least in part, based on specific interactions of agrin with other matrix molecules and with membrane-associated or integral membrane proteins of the abutting cells. This review summarizes studies concerning the integration of agrin with other molecules and highlights possible functions of agrin in the synaptic basal lamina and in other matrices.