The dense‐core vesicle maturation protein CCCP‐1 binds RAB‐2 and membranes through its C‐terminal domain

Abstract

Dense-core vesicles (DCVs) are secretory organelles that store and release modulatory neurotransmitters from neurons and endocrine cells. Recently, the conserved coiled-coil protein CCCP-1 was identified as a component of the DCV biogenesis pathway in the nematode C. elegans. CCCP-1 binds the small GTPase RAB-2 and colocalizes with it at the trans-Golgi. Here we report a structure-function analysis of CCCP-1 to identify domains of the protein important for its localization, binding to RAB-2, and function in DCV biogenesis. We find that the CCCP-1 C-terminal domain (CC3) has multiple activities. CC3 is necessary and sufficient for CCCP-1 localization and for binding to RAB-2, and is required for the function of CCCP-1 in DCV biogenesis. Additionally, CCCP-1 binds membranes directly through its CC3 domain, indicating that CC3 may comprise a previously uncharacterized lipid-binding motif. We conclude that CCCP-1 is a coiled-coil protein that binds an activated Rab and localizes to the Golgi via its C-terminus, properties similar to members of the golgin family of proteins. CCCP-1 also shares biophysical features with golgins; it has an elongated shape and forms oligomers.

An early endosome–derived retrograde trafficking pathway promotes secretory granule maturation

“…among a subset of SGs that require endosomal trafficking (Ailion et al, 2014;Azouz et al, 2014;Cattin-Ortolá et al, 2017;Klein et al, 2017;Sparvoli et al, 2018;Topalidou et al, 2016).…”

“…However, although AP-3 is required for targeting CD63 to mature WPBs and large dense core vesicles ( Grabner et al, 2006 ; Harrison-Lavoie et al, 2006 ), AP-3 is dispensable for glue granule maturation ( Burgess et al, 2012 ; this study). Nevertheless, the requirement for CD63- and PI4KII-dependent retrograde trafficking indicates that glue granules are among a subset of SGs that require endosomal trafficking ( Ailion et al, 2014 ; Azouz et al, 2014 ; Cattin-Ortolá et al, 2017 ; Klein et al, 2017 ; Sparvoli et al, 2018 ; Topalidou et al, 2016 ).…”

Extracellular vesicle budding is inhibited by redundant regulators of TAT-5 flippase localization and phospholipid asymmetry

“…To confirm that TAT-5 is mislocalized to late endosomes, we tested whether TAT-5 colocalizes with the Rab2 homolog UNC-108, which is found on the Golgi and recruited to endosomes after early endosome markers, such as RAB-5 and PI3P, and acts before late endosome markers, such as RAB-7 ( 31 , 32 ). GFP::TAT-5 colocalized with a subset of mCherry-tagged UNC-108 in control embryos, showing a positive Pearson’s coefficient ( Fig.…”

EIPR1 controls dense-core vesicle cargo retention and EARP complex localization in insulin-secreting cells

“…CCDC186/CCCP-1 is a coiled-coil protein that functions in DCV biogenesis in the same genetic pathway as EIPR1 and EARP (Cattin-Ortolá, Topalidou, et al, 2019), but is not required for transferrin recycling (Figure 8A). CCDC186 is localized near immature DCVs and the TGN (Ailion et al, 2014;Cattin-Ortolá et al, 2017;Cattin-Ortolá, Topalidou, et al, 2019), but is distinct from recycling endosomes marked by transferrin (Supplemental Figure S9A). Notably, localization of CCDC186 does not require EIPR1 (Supplemental Figure S9B).…”