Multi-functional ARF1 compartments serve as a hub for short-range cargo transfer to endosomes

Abstract

AbstractCellular membrane homeostasis is maintained via a tightly regulated membrane and cargo flow between organelles of the endocytic and secretory pathways. Adaptor protein complexes (APs), which are recruited to membranes by the small GTPase ARF1, facilitate cargo selection and incorporation into trafficking intermediates. According to the classical model, small vesicles would facilitate bi-directional long-range vesicular transport between the Golgi and endosomes. Here we revisit the intracellular organization of the vesicular sorting machinery using a combination of CRISPR-Cas9 gene editing, live-cell high temporal (fast-confocal) or spatial (stimulated emission depletion (STED)) microscopy as well as correlative light and electron microscopy. We characterize novel tubulo-vesicular ARF1 compartments that harbor clathrin and different APs, and coordinate Golgi export as well as endocytic recycling. Rather than long-range vesicle shuttling, we observe transient interactions of ARF1 compartments and recycling endosomes, with the sorting machinery localizing at the interface between the two membranes. Our findings suggest that endocytic and secretory cargo transfer from ARF1 compartments to endosomes may be mediated by a kiss-and-run mechanism rather than by fusion of transport vesicles.