Integrin-linked kinase controls neurite outgrowth in N1E-115 neuroblastomacells

Mouse N1E-115 cells grown on a laminin matrix exhibit neurite outgrowth in response to serum deprivation. Treatment of cells with an antibody against beta (1) integrin inhibits neurite outgrowth. Thus, beta (1) integrin is in volved in the neuritogenesis of N1E-115 cells on a laminin matrix. Integrin -linked kinase (ILK), a recently identified cytoplasmic serine/threonine pr otein kinase that binds to the cytoplasmic domain of beta (1) integrin, has an important role in transmembrane signal transduction via integrins. We r eport that ILK is expressed in N1E-115 cells, the expression levels of whic h are constant under both normal and differentiating conditions. A stable t ransfection of a kinase-deficient mutant of ILK (DN-ILK) results in inhibit ion of neurite outgrowth in serum-starved N1E-115 cells grown on laminin. O n the other hand, a transient expression of wild type ILK stimulated neurit e outgrowth. The ILK activity in the parental cells was transiently activat ed after seeding on the laminin matrix, whereas that in the DN-ILK-transfec ted cells was not. These results suggest that transient activation of ILK i s 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 aft er N1E-115 cell attachment to laminin, but not in the DN-ILK-expressed cell s. The time course of p38 MAP kinase activation was very similar to that of ILK activation. Furthermore, a p38 MAP kinase inhibitor, SB203580, signifi cantly blocked neurite outgrowth. Thus' activation of p38 MAP kinase is inv olved in ILK-mediated signal transduction leading to integrin-dependent neu rite outgrowth in N1E-115 cells.