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.
Highlights
Receptor-mediated endocytosis constitutes an important cellular mechanism to take nutrients into cells and transduce extracellular signals essential for cell homeostasis, proliferation, and differentiation
The molecules implicated in the assembly of clathrin-coated vesicles (CCV),3 including clathrin, AP-2, AP-180, dynamin and other proteins such as epsin, amphiphysin, and synaptotagmin, are known to serve as the substrates of either protein tyrosine or serine and threonine kinases [3]
Our recent in vitro analysis of Tfn sequestration using perforated cells demonstrates that depletion of cortactin in cytosol extracts weakens the formation of clathrin-coated vesicles [22], indicating that cortactin is important for clathrin-mediated endocytosis
Summary
Receptor-mediated endocytosis constitutes an important cellular mechanism to take nutrients into cells and transduce extracellular signals essential for cell homeostasis, proliferation, and differentiation. 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. the significance of cortactin tyrosine phosphorylation in endocytosis is unknown.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
