The diverse roles and multiple forms of focal adhesion kinase in brain

Although it was originally characterized as a constituent of focal adhesions in fibroblasts, focal adhesion kinase (FAK) is now considered to be not only a mediator of adhesion processes but also a crucial regulator of guidance and a modulator of gene expression. FAK is the main transducer of the integrin signaling required to stabilize the actin cytoskeleton. However, additional activities have been described over the years. In the brain, FAK deserves particular attention as it is found in various alternatively spliced forms - these distributed in multiple subcellular compartments or bound to multiple partners. Moreover, its signaling involves not only phosphorylation but also ubiquitination and proteolysis. Several experimental cell models demonstrate that FAK increases or decreases migration, participates in differentiation and contributes to plasticity events. In addition, this kinase is linked to cell survival in cancer and apoptosis. This review focuses on the diversity of events involving brain-located forms of FAK.