Staurosporine-induced morphological differentiation of human neuroblastoma cells

SH-SY-5Y human neuroblastoma cells rapidly elaborated an extensive network of neuritic processes following treatment with staurosporine, an inhibitor of protein kinase C. These neurites were retracted within 24hr following removal of inhibitor. Another inhibitor of protein kinase C, H7 [1-(5-isoquinolinesulfonyl)-2-methylpiperazine dihydrochloride], also induced rapid, reversible neurite outgrowth. However, neurites induced by these two inhibitors were morphologically distinct: staurosporine-treated cells elaborated a branching neuritic network adjacent to cell bodies, with some longer, unbranching neurites extending out of this network, while H7-treated cells elaborated only long, unbranching neurites. HA-1004 [N-(2-guanidinoethyl)-5-isoquinolinesulfonamide], which inhibits of cAMP- and cGMP-dependent protein kinases but not protein kinase C, did not induce neuritogenesis. Staurosporine-induced neurite outgrowth did not require protein synthesis but did require microtubule assembly, suggesting that cells contained the necessary components for neuritogenesis, and that alterations in protein phosphorylation alone was sufficient to initiate neurite outgrowth by rearrangement of existing structures or cytoskeletal precursors. These results implicate phosphorylation in the regulation of neuronal differentiation and neuritogenesis.