Integrin-linked Kinase Controls Neurite Outgrowth in N1E-115 Neuroblastoma Cells

Abstract

Mouse N1E-115 cells grown on a laminin matrix exhibit neurite outgrowth in response to serum deprivation. Treatment of cells with an antibody against β1 integrin inhibits neurite outgrowth. Thus, β 1 integrin is involved in the neuritogenesis of N1E-115 cells on a laminin matrix. Integrin-linked kinase (ILK), a recently identified cytoplasmic serine/threonine protein kinase that binds to the cytoplasmic domain of β1 integrin, has an important role in transmembrane signal transduction via integrins. We report that ILK is expressed in N1E-115 cells, the expression levels of which are constant under both normal and differentiating conditions. A stable transfection of a kinase-deficient mutant of ILK (DN-ILK) results in inhibition of neurite outgrowth in serum-starved N1E-115 cells grown on laminin. On the other hand, a transient expression of wild type ILK stimulated neurite outgrowth. The ILK activity in the parental cells was transiently activated after seeding on the laminin matrix, whereas that in the DN-ILK-transfected cells was not. These results suggest that transient activation of ILK is required for neurite outgrowth in serum-starved N1E-115 cells on laminin. Under the same conditions, p38 mitogen-activated protein (MAP) kinase, but neither MAP kinase/extracellular signal-regulated kinase kinase (MEK) nor extracellular signal-regulated kinases (ERK), was transiently activated after NIE-115 cell attachment to laminin, but not in the DN-ILK-expressed cells. The time course of p38 MAP kinase activation was very similar to that of ILK activation. Furthermore, a p38 MAP kinase inhibitor, SB203580, significantly blocked neurite outgrowth. Thus, activation of p38 MAP kinase is involved in ILK-mediated signal transduction leading to integrin-dependent neurite outgrowth in N1E-115 cells.