PTK2 and glioblastoma: Further evidence for the role of AMPA receptors in glioblastoma migration was provided by Piao and collaborators, who showed that expression of GluR1, the most abundant AMPAR subunit in glioblastoma, correlates with increased cell-surface expression of β1 integrin and phosphorylation of focal adhesion kinase (FAK), the molecules implicated in glioblastoma invasion.