Critical role of the FERM domain in Pyk2 stimulated glioma cell migration.

The strong tendency of malignant glioma cells to invade locally into surrounding normal brain precludes effective surgical resection, reduces the efficacy of radiotherapy, and is associated with increased resistance to chemotherapy regimens. We report that the N-terminal FERM domain of Pyk2 regulates its promigratory function. A 3-dimensional model of the Pyk2 FERM domain was generated and mutagenesis studies identified residues essential for Pyk2 promigratory function. Model-based targeted mutations within the FERM domain decreased Pyk2 phosphorylation and reduced the capacity of Pyk2 to stimulate glioma cell migration but did not significantly alter the intracellular distribution of Pyk2. Expression of autonomous Pyk2 FERM domain fragments containing analogous mutations exhibited reduced capacity to inhibit glioma cell migration and Pyk2 phosphorylation relative to expression of an autonomous wild type FERM domain fragment. These results indicate that the FERM domain plays an important role in regulating the functional competency of Pyk2 as a promigratory factor in glioma.

The tyrosine kinase pyk2 promotes migration and invasion of glioma cells.

Glioblastoma multiforme is extraordinarily aggressive due to the propensity of cells to migrate away from the tumor core into the surrounding normal brain. In this report, we investigated the role of proline-rich tyrosine kinase 2 (Pyk2) and FAK with regard to influencing glioma cell phenotypes. Expression of Pyk2 stimulated glioma cell migration, whereas expression of FAK inhibited glioma cell migration and stimulated cell cycle progression. Pyk2 autophosphorylation was necessary, but not sufficient, to stimulate cellular migration. The N-terminal domain of Pyk2 is required for stimulation of migration as an N-terminally deleted variant of Pyk2 failed to stimulate migration, whereas expression of an autonomous Pyk2 N-terminal domain inhibited cell migration. Substitution of the C-terminal domain of Pyk2 with the corresponding domain of FAK stimulated cell migration as effectively as wild-type Pyk2; however, substitution of the N-terminal domain of Pyk2 with that of FAK inhibited cell migration, substantiating that the N-terminal domain of Pyk2 was required to stimulate migration. Silencing of Pyk2 expression by RNA interference significantly inhibited glioma migration. Cell migration was restored on re-expression of Pyk2, but expression of FAK in Pyk2 knockdown cells failed to restore migration. We conclude that Pyk2 plays a central role in the migratory behavior of glioblastomas.