Sequence-Dependent Sorting of Recycling Proteins by Actin-Stabilized Endosomal Microdomains

SummaryThe functional consequences of signaling receptor endocytosis are determined by the endosomal sorting of receptors between degradation and recycling pathways. How receptors recycle efficiently, in a sequence-dependent manner that is distinct from bulk membrane recycling, is not known. Here, in live cells, we visualize the sorting of a prototypical sequence-dependent recycling receptor, the beta-2 adrenergic receptor, from bulk recycling proteins and the degrading delta-opioid receptor. Our results reveal a remarkable diversity in recycling routes at the level of individual endosomes, and indicate that sequence-dependent recycling is an active process mediated by distinct endosomal subdomains distinct from those mediating bulk recycling. We identify a specialized subset of tubular microdomains on endosomes, stabilized by a highly localized but dynamic actin machinery, that mediate this sorting, and provide evidence that these actin-stabilized domains provide the physical basis for a two-step kinetic and affinity-based model for protein sorting into the sequence-dependent recycling pathway.PaperFlick Help with MOV filesOptionsDownload video (37600 K)

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► B2AR is sorted into a specialized subset of tubules in the endosome and recycled
► A highly localized actin-based machinery stabilizes this subset of tubular domains
► This allows selective sequence-dependent entry of B2AR by regulated diffusion
► Actin binding via PDZ domains concentrates B2AR in these recycling domains