Essential role for integrin linked kinase in Akt-mediated integrin survival signaling in hippocampal neurons

Activation of integrin receptors in neurons can promote cell survival and synaptic plasticity, but the underlying signal transduction pathway(s) is unknown. We report that integrin signaling prevents apoptosis of embryonic hippocampal neurons by a mechanism involving integrin-linked kinase (ILK) that activates Akt kinase. Activation of integrins using a peptide containing the amino acid sequence EIKLLIS derived from the α chain of laminin protected hippocampal neurons from apoptosis induced by glutamate or staurosporine, and increased Akt activity in a β₁ integrin-dependent manner. Transfection of neurons with a plasmid encoding dominant negative Akt blocked the protective effect of the integrin-activating peptide, as did a chemical inhibitor of Akt. Although inhibitors of phosphoinositide-3 (PI3) kinase blocked the protective effect of the peptide, we found no increase in PI3 kinase activity following integrin stimulation suggesting that PI3 kinase was necessary for Akt activity but was not sufficient for the increase in Akt activity following integrin activation. Instead, we show a requirement for ILK in integrin receptorinduced Akt activation. ILK was activated following integrin stimulation and dominant negative ILK blocked integrinmediated Akt activation and cell survival. Activation of ILK and Akt were also required for neuroprotection by substrateassociated laminin. These results establish a novel pathway that signals cell survival in neurons in response to integrin receptor activation.