Receptor-mediated Endocytosis Involves Tyrosine Phosphorylation of Cortactin

Abstract

Efficient internalization of cell surface receptors requires actin polymerization mediated by Arp2/3 complex and cortactin, a prominent substrate of the protein-tyrosine kinase Src. However, the significance of cortactin tyrosine phosphorylation in endocytosis is unknown. We found that overexpression of a cortactin mutant deficient in tyrosine phosphorylation decreased transferrin uptake. Suppression of cortactin expression by RNA interference also reduced transferrin internalization. Such inhibition was effectively rescued by overexpressing wild-type cortactin but not a cortactin mutant deficient in tyrosine phosphorylation or a mutant with deletion of the Src homology 3 domain. Likewise, purified phosphorylation-null cortactin failed to restore the formation of clathrin-coated vesicles in a cortactin-depleted cell extract. In vitro analysis revealed that Src-mediated phosphorylation enhanced the association of cortactin with dynamin-2 in a tyrosine phosphorylation-dependent manner. Quantitative analysis demonstrated that Src enhances the affinity of cortactin for dynamin-2 by more than 3-fold. On the other hand, Src-treated dynamin-2 had no effect on its interaction with cortactin. These data indicate that Src kinase is implicated in clathrin-mediated endocytosis by phosphorylation of cortactin.

Multiple regulatory inputs converge on cortactin to control invadopodia biogenesis and extracellular matrix degradation

“…In this process, dynamin 2 could also affect the activity of the Arp2/3 complex indirectly through cortactin Krueger et al, 2003). Of note, recent findings have shown that Src-dependent phosphorylation of cortactin enhances its affinity for dynamin-2 more than threefold (Zhu et al, 2007), suggesting a possible molecular basis for the stimulatory effect of cortactin phosphorylation by SFK in invadopodia formation. An interesting twist might be provided by a recent report suggesting that cortactin functions in regulating matrix metalloprotease secretion at invadopodia (Clark et al, 2007).…”

The Endocytic Fate of the Transferrin Receptor Is Regulated by c-Abl Kinase

“…Based on our previous observations that Src kinase can regulate internalization and release of TfR1 containing clathrin-coated pits by tyrosine phosphorylation of Dyn2 and its actin binding partner cortactin (10,11), it is possible that several potential layers of regulation exist that mediate the internalization and trafficking of this trophic receptor.…”

“…However, recent studies by us and others (10,11) have suggested that the binding of the Tf ligand leads to the activation of Src kinase, which in turn promotes phosphorylation of specific components of the endocytic machinery such as dynamin 2 (Dyn2) and its actin-associated binding partner cortactin (12)(13)(14)(15)(16). The Src-mediated phosphorylation event of these specific endocytic components appears to be essential for efficient assembly and scission of clathrin-coated pits that are utilized to internalize this receptor-ligand complex.…”

microRNA-182 inhibits the proliferation and invasion of human lung adenocarcinoma cells through its effect on human cortical actin-associated protein

“…There is increasing evidence supporting that cortactin is a prominent substrate of Src-protein-tyrosine kinase (18,26), and that tyrosine phosphorylation of cortactin occurs frequently in response to various extracellular stimuli, including growth factors, bacterially-mediated phagocytosis, cell shrinkage and membrane injury. Although studies have found that the introduction of a mutant cortactin deficient in tyrosine phosphorylation impairs cell motility, tumor invasion, invadopodia, and podosome formation (18,20,27,28), and that cortactin plays important roles in tumor growth, there have been few reports on the role of cortactin regulation in tumors by epigenetic modification.…”