Discrete GPCR-triggered endocytic modes enable β-arrestins to flexibly regulate cell signaling

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Abstract

β-arrestins are master regulators of cellular signaling that operate by desensitizing ligand-activated G protein-coupled receptors (GPCRs) at the plasma membrane and promoting their subsequent endocytosis. The endocytic activity of β-arrestins is ligand-dependent, triggered by GPCR binding, and increasingly recognized to have a multitude of downstream signaling and trafficking consequences that are specifically programmed by the bound GPCR. However, only one biochemical 'mode' for GPCR-mediated triggering of the endocytic activity is presently known- displacement of the β-arrestin C-terminus (CT) to expose CCP-binding determinants that are masked in the inactive state. Here we revise this view by uncovering a second mode of GPCR-triggered endocytic activity that is independent of the β-arrestin CT and, instead, requires the cytosolic base of the β-arrestin C-lobe (CLB). We further show each of the discrete endocytic modes is triggered in a receptor-specific manner, with GPCRs that bind β-arrestin transiently ('class A') primarily triggering the CLB-dependent mode and GPCRs that bind more stably ('class B') triggering both the CT and CLB -dependent modes in combination. Moreover, we show that different modes have opposing effects on the net signaling output of receptors- with the CLB-dependent mode promoting rapid signal desensitization and the CT-dependent mode enabling prolonged signaling. Together, these results fundamentally revise understanding of how β-arrestins operate as efficient endocytic adaptors while facilitating diversity and flexibility in the control of cell signaling.

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All numerical data used to generate the figures has been included in the supporting data file. Source data for each figure panel is included as a separate worksheet in the combined excel document.

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Benjamin Barsi-Rhyne

Tetrad Graduate Program, University of California, San Francisco, San Francisco, United States

Competing interests
The authors declare that no competing interests exist.
Aashish Manglik

Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, United States

For correspondence
Aashish.Manglik@ucsf.edu

Competing interests
The authors declare that no competing interests exist.
Mark von Zastrow

Department of Psychiatry and Behavioral Sciences, University of California, San Francisco, San Francisco, United States

For correspondence
mark.vonzastrow@ucsf.edu

Competing interests
The authors declare that no competing interests exist.

"This ORCID iD identifies the author of this article:" 0000-0003-1375-6926

Funding

NIH Office of the Director (DP5OD023048)

Aashish Manglik

National Institutes of Health (R01DA010711)

Mark von Zastrow

National Institutes of Health (R01DA012864)

Mark von Zastrow

American Heart Association (19PRE34380570)

Benjamin Barsi-Rhyne

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

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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.