Macropinocytosis of the PDGF β-receptor promotes fibroblast transformation by H-RasG12V

Research output: Contribution to journalArticlepeer-review


  • C Schmees
  • R Villaseñor
  • W Zheng
  • H Ma
  • M Zerial
  • C-H Heldin
  • C Hellberg

Colleges, School and Institutes


Receptor tyrosine kinase (RTK) signaling is frequently increased in tumor cells, sometimes as a result of decreased receptor down-regulation. The extent to which the endocytic trafficking routes can contribute to such RTK hyperactivation is unclear. Here, we show for the first time that fibroblast transformation by H-RasG12V induces the internalization of platelet-derived growth factor β-receptor (PDGFRβ) by macropinocytosis, enhancing its signaling activity and increasing anchorage-independent proliferation. H-RasG12V transformation and PDGFRβ activation were synergistic in stimulating phosphatidylinositol (PI) 3-kinase activity, leading to receptor macropinocytosis. PDGFRβ macropinocytosis was both necessary and sufficient for enhanced receptor activation. Blocking macropinocytosis by inhibition of PI 3-kinase prevented the increase in receptor activity in transformed cells. Conversely, increasing macropinocytosis by Rabankyrin-5 overexpression was sufficient to enhance PDGFRβ activation in nontransformed cells. Simultaneous stimulation with PDGF-BB and epidermal growth factor promoted macropinocytosis of both receptors and increased their activation in nontransformed cells. We propose that H-Ras transformation promotes tumor progression by enhancing growth factor receptor signaling as a result of increased receptor macropinocytosis.


Original languageEnglish
Pages (from-to)2571-82
Number of pages12
JournalMolecular Biology of the Cell
Issue number13
Publication statusPublished - 2012