The Golgi apparatus is a multi-compartment central sorting station at the intersection of secretory and endocytic vesicular traffic. The mechanisms that permit cargo-loaded transport vesicles from different origins to selectively access different Golgi compartments are incompletely understood. Here, we develop a re-routing and capture assay to investigate systematically the vesicle-tethering activities of ten widely conserved golgin coiled-coil proteins. We find that subsets of golgins with distinct localizations on the Golgi surface have capture activities toward vesicles of different origins. These findings demonstrate that golgins act as tethers in vivo, and hence the specificity we find to be encoded in this tethering is likely to make a major contribution to the organization of membrane traffic at the Golgi apparatus.The functionality of the membrane-bound organelles of eukaryotic cells is determined by their constituent proteins and lipids. A major determinant of organelle composition in the endomembrane system is the highly selective transfer of cargo-laden vesicles between compartments. Not only should the correct cargo be collected at the origin, but the transport vesicle must be selectively delivered to the correct destination. SNARE proteins on the vesicle and destination organelle assemble to drive membrane fusion (1). The diversity of cellular SNAREs, their differential localization, and their selective pairwise interactions implicate them in contributing specificity to membrane traffic (2-4). However, the relatively small size of SNAREs means they can only interact after a vesicle is closely apposed to its potential destination. A process called 'tethering' is thought to attach the vesicle to the organelle before SNARE complex assembly (5-7). The degree to which organelle tethers confer specificity rather than efficiency to membrane traffic is presently unclear.To investigate this problem, we focused on the Golgi apparatus, the central sorting station in the endomembrane system (8). The Golgi is a stack of distinct cisternae arranged from cis to trans, and particular vesicles appear to preferentially fuse with different cisternae within the stack. For example, vesicles derived from the endoplasmic reticulum (ER) deliver cargo to the cis face of the Golgi, while those from the endocytic pathway deliver cargo to the trans Golgi. Moreover, vesicles mediate selective transfer of contents between Golgi cisternae. Thus, providing spatial cues to vesicles arriving at the Golgi is critical for endomembrane traffic and represents an ideal system to investigate the basis of vesicle targeting specificity. One set of candidate vesicle tethers at the Golgi is the "golgins", large well conserved coiled-coil proteins anchored to the membrane via their C-termini (9-11). The golgins have been suggested to act as tethers but in vivo evidence for this role is lacking (12, 13). In addition, other roles have been proposed for some golgins include recruiting kinases or cytoskeletal regulators (14,15). Golgin mut...

BackgroundThe internal organization of cells depends on mechanisms to ensure that transport carriers, such as vesicles, fuse only with the correct destination organelle. Several types of proteins have been proposed to confer specificity to this process, and we have recently shown that a set of coiled-coil proteins on the Golgi, called golgins, are able to capture specific classes of carriers when relocated to an ectopic location.ResultsMapping of six different golgins reveals that, in each case, a short 20–50 residue region is necessary and sufficient to capture specific carriers. In all six of GMAP-210, golgin-84, TMF, golgin-97, golgin-245, and GCC88, this region is located at the extreme N-terminus of the protein. The vesicle-capturing regions of GMAP-210, golgin-84, and TMF capture intra-Golgi vesicles and share some sequence features, suggesting that they act in a related, if distinct, manner. In the case of GMAP-210, this shared feature is in addition to a previously characterized “amphipathic lipid-packing sensor” motif that can capture highly curved membranes, with the two motifs being apparently involved in capturing distinct types of vesicles. Of the three GRIP domain golgins that capture endosome-to-Golgi carriers, golgin-97 and golgin-245 share a closely related capture motif, whereas that in GCC88 is distinct, suggesting that it works by a different mechanism and raising the possibility that the three golgins capture different classes of endosome-derived carriers that share many cargos but have distinct features for recognition at the Golgi.ConclusionsFor six different golgins, the capture of carriers is mediated by a short region at the N-terminus of the protein. There appear to be at least four different types of motif, consistent with specific golgins capturing specific classes of carrier and implying the existence of distinct receptors present on each of these different carrier classes.

Highlights d Tissue recovers robust migration in the continued presence of a chemokine flood d Chemokine-driven phosphorylation triggers recycling of the scavenger receptor Cxcr7b d Phospho-deficient Cxcr7b mediates migration but not adaption to elevated chemokine levels d Adaptation to chemokine changes outsourced from the guidance receptor Cxcr4 to Cxcr7b

Quantitative microscopy is becoming increasingly crucial in efforts to disentangle the complexity of organogenesis, yet adoption of the potent new toolbox provided by modern data science has been slow, primarily because it is often not directly applicable to developmental imaging data. We tackle this issue with a newly developed algorithm that uses point cloud-based morphometry to unpack the rich information encoded in 3D image data into a straightforward numerical representation. This enabled us to employ data science tools, including machine learning, to analyze and integrate cell morphology, intracellular organization, gene expression and annotated contextual knowledge. We apply these techniques to construct and explore a quantitative atlas of cellular architecture for the zebrafish posterior lateral line primordium, an experimentally tractable model of complex self-organized organogenesis. In doing so, we are able to retrieve both previously established and novel biologically relevant patterns, demonstrating the potential of our data-driven approach.