Growth factor modulation of substrate-specific morphological patterns in Aplysia bag cell neurons.

Components of the extracellular matrix (ECM) can act not only as passive substrates for neuronal attachment and outgrowth but also as active sites for signal transduction. Thus, specific ECM components may modulate effects of growth factors (GFs) that play an important role in structural changes in development and adult neuronal plasticity. In this study we examined the interaction of cultured Aplysia bag cell neurons (BCNs) with components of ECM and different GFs. Different ECM substrata induce a substrate-specific BCN morphology: BCNs grown on collagen or poly-L-lysine have larger soma diameter and more extensive neurite outgrowth than BCNs grown on laminin or fibronectin. BCNs also interact in a substrate-dependent way with GFs: BDNF treatment leads to a reduction of outgrowth on poly-L-lysine but an enhancement on fibronectin and laminin. CNTF reduces the soma diameter on collagen IV but enlarges it on laminin or fibronectin. In contrast, NGF induces a reduction of both soma diameter and outgrowth, on all substrata. Plating of BCNs in the presence of anti-beta1-integrin reduces adhesion to fibronectin but does not change outgrowth. In contrast, RGD peptides block adhesion to laminin and poly-L-lysine and, additionally, reduce outgrowth on laminin. These data suggest that BCNs use different beta1-integrin-dependent as well as RGD-dependent mechanisms for adhesion and outgrowth on different ECM substrata, providing possible sites of modulation by specific GFs.