WNT Activates the AAK1 Kinase to Promote Clathrin-Mediated Endocytosis of LRP6 and Establish a Negative Feedback Loop

Cell Rep. 2019 Jan 2;26(1):79-93.e8. doi: 10.1016/j.celrep.2018.12.023.

Abstract

β-Catenin-dependent WNT signal transduction governs development, tissue homeostasis, and a vast array of human diseases. Signal propagation through a WNT-Frizzled/LRP receptor complex requires proteins necessary for clathrin-mediated endocytosis (CME). Paradoxically, CME also negatively regulates WNT signaling through internalization and degradation of the receptor complex. Here, using a gain-of-function screen of the human kinome, we report that the AP2 associated kinase 1 (AAK1), a known CME enhancer, inhibits WNT signaling. Reciprocally, AAK1 genetic silencing or its pharmacological inhibition using a potent and selective inhibitor activates WNT signaling. Mechanistically, we show that AAK1 promotes clearance of LRP6 from the plasma membrane to suppress the WNT pathway. Time-course experiments support a transcription-uncoupled, WNT-driven negative feedback loop; prolonged WNT treatment drives AAK1-dependent phosphorylation of AP2M1, clathrin-coated pit maturation, and endocytosis of LRP6. We propose that, following WNT receptor activation, increased AAK1 function and CME limits WNT signaling longevity.

Keywords: AAK1; AP2M1; LRP6; WNT signaling; clathrin; endocytosis; feedback loop; gain-of-function screen; kinase.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Clathrin / metabolism*
  • Endocytosis / physiology*
  • Feedback, Physiological
  • HEK293 Cells
  • Humans
  • Low Density Lipoprotein Receptor-Related Protein-6 / metabolism*
  • Male
  • Mice
  • Protein Kinase Inhibitors / pharmacology
  • Protein-Serine-Threonine Kinases / antagonists & inhibitors
  • Protein-Serine-Threonine Kinases / metabolism*
  • Wnt Proteins / metabolism*
  • Wnt Signaling Pathway / physiology*

Substances

  • Clathrin
  • LRP6 protein, human
  • Low Density Lipoprotein Receptor-Related Protein-6
  • Lrp6 protein, mouse
  • Protein Kinase Inhibitors
  • Wnt Proteins
  • AAK1 protein, human
  • Aak1 protein, mouse
  • Protein-Serine-Threonine Kinases