Fig. 2

β-arrestins influence trafficking of Cxcr7b into and out of Lamp1-positive endosomes. (A) Snapshots from supplementary material Movie 1 (example 1) showing that a Cxcr7-EGFP-labeled vesicle enters (arrow, upper panels) and splits from (arrow, lower panels) the Lamp1-DsRedmonomer-labeled endosomes in control cells. Time stamps indicate minutes:seconds. First frame corresponds to 1:33 (upper left) and 2:36 (lower left) in supplementary material Movie 1. (B) In cells lacking β-arrestin, Cxcr7-EGFP-labeled vesicles fuse with Lamp1-DsRedmonomer vesicles. First time point corresponds to 2:54 in supplementary material Movie 2. Arrow marks the vesicle of interest. (C) Illustration of a transplantation experiment. Images illustrate decay of the Cxcl12a-EGFP signal, relative to that of the receptor (supplementary material Movie 3). Arrow points at the vesicle of interest. (D) Representation of the internalization and subsequent recycling of Cxcr7b to the cell membrane after targeting Cxcl12a to degradation (left). In the absence of β-arrestin, Cxcr7b accumulates in late endosomes, compromising sink function (right).