Protein synthesis and mRNA in isolated growth cones from differentiating SH-SY5Y neuroblastoma cells

The human neuroblastoma cell line, SH-SY5Y, differentiates into a neuronal, sympathetic phenotype in the presence of phorbol ester and serum. Growth cones prepared from differentiating SH-SY5Y cells have characteristics similar to those of growth cones from embryonic rat brain. In addition, SH-SY5Y growth cones contain ribosomes. In this study we show, by metabolic labeling of isolated growth cones, that local protein synthesis occurred in these structures. The pattern of labeled proteins was very similar to that of the corresponding cell body fraction. RNA was shown to be transported to the growth cone compartment, and by in situ hybridization. beta-actin mRNA could be visualized in intact neuritic growth cones. Comparison by Northern blot hybridizations of RNA prepared from growth cones and cell bodies, respectively, showed that mRNAs coding for growth-associated protein 43, microtubule-associated protein 2, actin, neuropeptide tyrosine, and glyceraldehyde-3-phosphate dehydrogenase were present in both fractions. In contrast, mRNAs coding for the nuclear proteins c-jun and N-myc were virtually absent in the growth cone, but readily detectable in the cell body preparation. The selective distribution of mRNAs to the growth cones was not restricted to stable, abundant mRNA species, since mRNA coding for the insulin-like growth factor I receptor was stable, but not present in growth cones. Thus, differentiating SH-SY5Y cells can sort and transport RNA to the growth cone compartment, suggesting that this system of clonal cells could be useful to unravel mechanisms involved in the compartmentalization of mRNA.