DIFFERENTIAL EXPRESSION OF UBIQUITOUS AND NEURONAL KINESIN HEAVY-CHAINS DURING DIFFERENTIATION OF HUMAN NEUROBLASTOMA AND PC12 CELLS

Kinesin is a microtubule-based motor protein involved in intracellular organelle transport. Neurons are characterized by the presence of at least two isoforms of conventional kinesin: ubiquitous kinesin, expres sed in all cells and tissues, and neuronal kinesin, whose pattern of e xpression is confined to neuronal cells. In order to investigate wheth er the two kinesin motors, which are encoded by different genes, may p lay distinct biological roles in neurons, we studied their expression during neuronal differentiation. Human neuroblastoma SH-SY5Y and IMR32 cells and rat phaeochromocytoma PC12 cells were used as an in vitro s ystem for neuronal differentiation and were induced to differentiate i n the presence of retinoic acid, a combination of dibutyryl cAMP and 5 -bromodeoxyuridine, and nerve growth factor respectively. The expressi on level of each kinesin isoform was evaluated by quantitative immunob lot before and after pharmacological treatment. We found that in all c ell types the expression level of neuronal kinesin, but not of ubiquit ous kinesin, is stimulated during differentiation. In particular, SH-S Y5Y cells show a 4.5-fold, IMR32 cells a 3-fold and PC12 cells a 7-fol d increase in the level of expression of neuronal kinesin. By Northern blot analysis we found that the selective increase in the expression of neuronal kinesin is paralleled by an increase in its mRNA, indicati ng that there is a transcriptional control of the expression of this k inesin isoform during differentiation of neuroblastoma and PC12 cells. Our results suggest that these cells represent an adequate model to s tudy the function of conventional kinesin and its isoforms.