Integration of GPCR Signaling and Sorting from Very Early Endosomes via Opposing APPL1 Mechanisms

Silvia Sposini, Frederic G. Jean-Alphonse, Mohammed A. Ayoub, Affiong Oqua, Camilla West, Stuart Lavery, Jan J. Brosens, Eric Reiter, Aylin C. Hanyaloglu

Research output: Contribution to journalArticlepeer-review

65 Citations (Scopus)


Endocytic trafficking is a critical mechanism for cells to decode complex signaling pathways, including those activated by G-protein-coupled receptors (GPCRs). Heterogeneity in the endosomal network enables GPCR activity to be spatially restricted between early endosomes (EEs) and the recently discovered endosomal compartment, the very early endosome (VEE). However, the molecular machinery driving GPCR activity from the VEE is unknown. Using luteinizing hormone receptor (LHR) as a prototype GPCR for this compartment, along with additional VEE-localized GPCRs, we identify a role for the adaptor protein APPL1 in rapid recycling and endosomal cAMP signaling without impacting the EE-localized β2-adrenergic receptor. LHR recycling is driven by receptor-mediated Gαs/cAMP signaling from the VEE and PKA-dependent phosphorylation of APPL1 at serine 410. Receptor/Gαs endosomal signaling is localized to microdomains of heterogeneous VEE populations and regulated by APPL1 phosphorylation. Our study uncovers a highly integrated inter-endosomal communication system enabling cells to tightly regulate spatially encoded signaling. Sposini et al. report that G-protein signaling from specific GPCRs is spatially restricted in very early endosomes (VEEs), compartments distinct from classic early endosomes. Mechanistically, receptor signaling and sorting from VEEs occur via opposing phosphorylation states of APPL1 adaptor protein, providing novel decoding mechanisms for cells to tightly control signaling.

Original languageEnglish
Pages (from-to)2855-2867
Number of pages13
JournalCell Reports
Issue number10
Publication statusPublished - Dec 5 2017
Externally publishedYes


  • APPL1
  • G-protein-coupled receptor
  • cAMP
  • endosome
  • recycling

ASJC Scopus subject areas

  • General Biochemistry,Genetics and Molecular Biology


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