In vitro reconstitution reveals phosphoinositides as cargo-release factors and activators of the ARF6 GAP ADAP1

Proc Natl Acad Sci U S A. 2021 Jan 5;118(1):e2010054118. doi: 10.1073/pnas.2010054118. Epub 2020 Dec 18.


The differentiation of cells depends on a precise control of their internal organization, which is the result of a complex dynamic interplay between the cytoskeleton, molecular motors, signaling molecules, and membranes. For example, in the developing neuron, the protein ADAP1 (ADP-ribosylation factor GTPase-activating protein [ArfGAP] with dual pleckstrin homology [PH] domains 1) has been suggested to control dendrite branching by regulating the small GTPase ARF6. Together with the motor protein KIF13B, ADAP1 is also thought to mediate delivery of the second messenger phosphatidylinositol (3,4,5)-trisphosphate (PIP3) to the axon tip, thus contributing to PIP3 polarity. However, what defines the function of ADAP1 and how its different roles are coordinated are still not clear. Here, we studied ADAP1's functions using in vitro reconstitutions. We found that KIF13B transports ADAP1 along microtubules, but that PIP3 as well as PI(3,4)P2 act as stop signals for this transport instead of being transported. We also demonstrate that these phosphoinositides activate ADAP1's enzymatic activity to catalyze GTP hydrolysis by ARF6. Together, our results support a model for the cellular function of ADAP1, where KIF13B transports ADAP1 until it encounters high PIP3/PI(3,4)P2 concentrations in the plasma membrane. Here, ADAP1 disassociates from the motor to inactivate ARF6, promoting dendrite branching.

Keywords: PIP3 signaling; in vitro reconstitution; microtubule transport; neuronal development; small GTPases.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • ADP-Ribosylation Factor 6
  • ADP-Ribosylation Factors / metabolism*
  • ADP-Ribosylation Factors / physiology
  • Adaptor Proteins, Signal Transducing / metabolism*
  • Adaptor Proteins, Signal Transducing / physiology
  • Animals
  • Axons / metabolism
  • Biological Transport / physiology
  • Cell Membrane / metabolism
  • Cytoskeleton / metabolism
  • GTPase-Activating Proteins / metabolism
  • Humans
  • Inositol Phosphates / metabolism
  • Kinesins / metabolism
  • Microtubules / metabolism
  • Nerve Tissue Proteins / metabolism*
  • Nerve Tissue Proteins / physiology
  • Phosphatidylinositol Phosphates / metabolism
  • Phosphatidylinositols / metabolism*
  • Signal Transduction


  • ADAP1 protein, human
  • ADP-Ribosylation Factor 6
  • Adaptor Proteins, Signal Transducing
  • GTPase-Activating Proteins
  • Inositol Phosphates
  • Nerve Tissue Proteins
  • Phosphatidylinositol Phosphates
  • Phosphatidylinositols
  • KIF13B protein, human
  • Kinesins
  • ADP-Ribosylation Factors
  • ARF6 protein, human