1. Cell Biology
  2. Structural Biology and Molecular Biophysics
Download icon

A structural mechanism for phosphorylation-dependent inactivation of the AP2 complex

  1. Edward A Partlow
  2. Richard W Baker  Is a corresponding author
  3. Gwendolyn M Beacham
  4. Joshua S Chappie
  5. Andres E Leschziner  Is a corresponding author
  6. Gunther Hollopeter  Is a corresponding author
  1. Cornell University, United States
  2. University of California, San Diego, United States
Research Advance
  • Cited 1
  • Views 2,480
  • Annotations
Cite this article as: eLife 2019;8:e50003 doi: 10.7554/eLife.50003

Abstract

Endocytosis of transmembrane proteins is orchestrated by the AP2 clathrin adaptor complex. AP2 dwells in a closed, inactive state in the cytosol, but adopts an open, active conformation on the plasma membrane. Membrane-activated complexes are also phosphorylated, but the significance of this mark is debated. We recently proposed that NECAP negatively regulates AP2 by binding open and phosphorylated complexes (Beacham et al., 2018). Here, we report high-resolution cryo-EM structures of NECAP bound to phosphorylated AP2. The site of AP2 phosphorylation is directly coordinated by residues of the NECAP PHear domain that are predicted from genetic screens in C. elegans. Using membrane mimetics to generate conformationally open AP2, we find that a second domain of NECAP binds these complexes and cryo-EM reveals both domains of NECAP engaging closed, inactive AP2. Assays in vitro and in vivo confirm these domains cooperate to inactivate AP2. We propose that phosphorylation marks adaptors for inactivation.

Data availability

The density maps generated during this study are available at the Electron Microscopy Data Bank (EMD-20215, unclamped and EMD-20220, clamped). The atomic structures generated during this study are available at the Protein Data Bank (PDB 6OWO, unclamped and 6OXL, clamped).

Article and author information

Author details

  1. Edward A Partlow

    Department of Molecular Medicine, Cornell University, Ithaca, United States
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0001-5513-088X
  2. Richard W Baker

    Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, United States
    For correspondence
    ribaker@ucsd.edu
    Competing interests
    The authors declare that no competing interests exist.
  3. Gwendolyn M Beacham

    Department of Molecular Medicine, Cornell University, Ithaca, United States
    Competing interests
    The authors declare that no competing interests exist.
  4. Joshua S Chappie

    Department of Molecular Medicine, Cornell University, Ithaca, United States
    Competing interests
    The authors declare that no competing interests exist.
  5. Andres E Leschziner

    Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, United States
    For correspondence
    aleschziner@ucsd.edu
    Competing interests
    The authors declare that no competing interests exist.
  6. Gunther Hollopeter

    Department of Molecular Medicine, Cornell University, Ithaca, United States
    For correspondence
    gh383@cornell.edu
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-6409-0530

Funding

National Institute of General Medical Sciences (R01 GM127548-01A1)

  • Gunther Hollopeter

Damon Runyon Cancer Research Foundation (DRG-#2285-17)

  • Richard W Baker

National Science Foundation (DGE-1650441)

  • Gwendolyn M Beacham

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Reviewing Editor

  1. Suzanne R Pfeffer, Stanford University School of Medicine, United States

Publication history

  1. Received: July 9, 2019
  2. Accepted: August 28, 2019
  3. Accepted Manuscript published: August 29, 2019 (version 1)
  4. Version of Record published: September 10, 2019 (version 2)

Copyright

© 2019, Partlow et al.

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.

Metrics

  • 2,480
    Page views
  • 440
    Downloads
  • 1
    Citations

Article citation count generated by polling the highest count across the following sources: Crossref, PubMed Central, Scopus.

Download links

A two-part list of links to download the article, or parts of the article, in various formats.

Downloads (link to download the article as PDF)

Download citations (links to download the citations from this article in formats compatible with various reference manager tools)

Open citations (links to open the citations from this article in various online reference manager services)

Further reading

    1. Cell Biology
    Jennifer M Kunselman et al.
    Research Article Updated

    Many signal transduction systems have an apparent redundancy built into them, where multiple physiological agonists activate the same receptors. Whether this is true redundancy, or whether this provides an as-yet unrecognized specificity in downstream signaling, is not well understood. We address this question using the kappa opioid receptor (KOR), a physiologically relevant G protein-coupled receptor (GPCR) that is activated by multiple members of the Dynorphin family of opioid peptides. We show that two related peptides, Dynorphin A and Dynorphin B, bind and activate KOR to similar extents in mammalian neuroendocrine cells and rat striatal neurons, but localize KOR to distinct intracellular compartments and drive different post-endocytic fates of the receptor. Strikingly, localization of KOR to the degradative pathway by Dynorphin A induces sustained KOR signaling from these compartments. Our results suggest that seemingly redundant endogenous peptides can fine-tune signaling by regulating the spatiotemporal profile of KOR signaling.

    1. Cell Biology
    2. Neuroscience
    Vladimir Zhemkov et al.
    Research Article

    Sigma 1 receptor (S1R) is a 223-amino-acid-long transmembrane endoplasmic reticulum (ER) protein. S1R modulates activity of multiple effector proteins and is a well-established drug target. However, signaling functions of S1R in cells are poorly understood. Here, we test the hypothesis that biological activity of S1R in cells can be explained by its ability to interact with cholesterol and to form cholesterol-enriched microdomains in the ER membrane. By performing experiments in reduced reconstitution systems, we demonstrate direct effects of cholesterol on S1R clustering. We identify a novel cholesterol-binding motif in the transmembrane region of human S1R. Mutations of this motif impair association of recombinant S1R with cholesterol beads, affect S1R clustering in vitro and disrupt S1R subcellular localization. We demonstrate that S1R-induced membrane microdomains have increased local membrane thickness and that increased local cholesterol concentration and/or membrane thickness in these microdomains can modulate signaling of inositol-requiring enzyme 1α in the ER. Further, S1R agonists cause disruption of S1R clusters, suggesting that biological activity of S1R agonists is linked to remodeling of ER membrane microdomains. Our results provide novel insights into S1R-mediated signaling mechanisms in cells.