JIP4 is recruited by the phosphoinositide-binding protein Phafin2 to promote recycling tubules on macropinosomes

J Cell Sci. 2021 Jul 15;134(14):jcs258495. doi: 10.1242/jcs.258495. Epub 2021 Jul 20.


Macropinocytosis allows cells to take up extracellular material in a non-selective manner into large vesicles called macropinosomes. After internalization, macropinosomes acquire phosphatidylinositol 3-phosphate (PtdIns3P) on their limiting membrane as they mature into endosomal-like vesicles. The molecular mechanisms that underlie recycling of membranes and transmembrane proteins from these macropinosomes still need to be defined. Here, we report that JIP4 (officially known as SPAG9), a protein previously described to bind to microtubule motors, is recruited to tubulating subdomains on macropinosomes by the PtdIns3P-binding protein Phafin2 (officially known as PLEKHF2). These JIP4-positive tubulating subdomains on macropinosomes contain F-actin, the retromer recycling complex and the retromer cargo VAMP3. Disruption of the JIP4-Phafin2 interaction, deletion of Phafin2 or inhibition of PtdIns3P production by VPS34 impairs JIP4 recruitment to macropinosomes. Whereas knockout of JIP4 suppresses tubulation, its overexpression enhances tubulation from macropinosomes. JIP4-knockout cells display increased retention of macropinocytic cargo in both early and late macropinosomes. Collectively, these data identify JIP4 and Phafin2 as components of a tubular recycling pathway that operates from macropinosomes. This article has an associated First Person interview with the first author of the paper.

Keywords: Endosomes; Macropinocytosis; Membrane recycling; Trafficking.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing* / genetics
  • Adaptor Proteins, Signal Transducing* / metabolism
  • Carrier Proteins* / genetics
  • Carrier Proteins* / metabolism
  • Endosomes / metabolism
  • Humans
  • Phosphatidylinositols* / metabolism
  • Pinocytosis
  • Protein Binding
  • Protein Transport
  • Vesicular Transport Proteins* / genetics
  • Vesicular Transport Proteins* / metabolism


  • Adaptor Proteins, Signal Transducing
  • Carrier Proteins
  • PLEKHF2 protein, human
  • Phosphatidylinositols
  • SPAG9 protein, human
  • Vesicular Transport Proteins