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 su bstrates for neuronal attachment and ougrowth 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 d evelopment and adult neuronal plasticity. In this study we examined the int eraction 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 diame ter and more extensive neurite outgrowth than BCNs grown on laminin or frbr onectin. BCNs also interact in a substrate-dependent way with GFs: BDNF tre atment leads to a reduction of outgrowth on poly-L-lysine but an enhancemen t on frbronectin and laminin. CNTF reduces the soma diameter on collagen IV but enlarges it on laminin or fibronectin. In contrast, NGF induces a redu ction of both soma diameter and outgrowth, on all substrate. Plating of BCN s in the presence of anti-beta 1-integrin reduces adhesion to frbronectin b ut does not change outgrowth. In contrast, RGD peptides block adhesion to l aminin and poly-L-lysine and, additionally, reduce outgrowth on laminin. Th ese data suggest that BCNs use different beta 1-integrin-dependent as well as RGD-dependent mechanisms for adhesion and outgrowth on different ECM sub strata, providing possible sites of modulation by specific GFs.