Human neuroblastoma cell differentiation requires protein kinase C-θ

Neuroblastoma LAN-5 cells exposed to retinoic acid cease to multiply and extend neurite outgrowths acquiring a neuronal phenotype. We now report that protein kinase C-θ (PKC-θ) isozyme is involved in this differentiation process due to the following findings: (i) PKC-θ is expressed by LAN-5 cells as a nuclear and perinuclear protein; (ii) cell stimulation with retinoic acid promotes in a large increase in the expression level of the kinase and its intracellular redistribution; and (iii) a PKC-θ antisense oligonucleotide reduces at the same time the expression level of the kinase and the cell response to retinoic acid. Altogether these data are consistent with a specific role played by PKC-θ in the differentiation program of neuronal cells.