Tissue transglutaminase is essential for neurite outgrowth in human neuroblastoma SH-SY5Y cells

Tissue transglutaminase is a normal constituent of the central and peripher al nervous systems and in rats transglutaminase activity in brain and spina l cord is highest during fetal stages when axonal outgrowth is occurring. F urther, treatment of human neuroblastoma SH-SY5Y cells with retinoic acid r esults in the cells withdrawing from the cell cycle and extending neurites, in the same time frame that tissue transglutaminase expression significant ly increases. Considering these and other previous findings, this study was carried out to determine whether tissue transglutaminase is involved in ne uronal differentiation of SH-SY5Y cells. For these studies SH-SY5Y cells st ably overexpressing wild-type tissue transglutaminase, an inactive tissue t ransglutaminase mutant (C277S) or an antisense tissue transglutaminase cons truct (which decreased endogenous tissue transglutaminase below detectable levels) were used. SH-SY5Y cells overexpressing wild-type tissue transgluta minase spontaneously differentiated into a neuronal phenotype when grown in low-serum media. In contrast, cells overexpressing inactive tissue transgl utaminase or the antisense tissue transglutaminase continued to proliferate and exhibit a flat polygenic morphology even when maintained in low-serum conditions. In addition, increased tissue transglutaminase expression in re sponse to retinoic acid was abolished in the antisense tissue transglutamin ase cells, and antisense and mutant tissue transglutaminase expressing cell s did not extend neurites in response to retinoic acid. Moreover, wild-type and inactive tissue transglutaminase exhibited differential intracellular localization. These data indicate that tissue transglutaminase is necessary and sufficien t for neuronal differentiation of human neuroblastoma SH-SY5Y cells. (C) 20 01 IBRO. Published by Elsevier Science Ltd. All rights reserved.