ABSTRACT
Collagen export from the endoplasmic reticulum (ER) requires TANGO1, COPII coats, and retrograde fusion of ERGIC membranes. How do these components come together to produce a transport carrier commensurate with the bulky cargo collagen? TANGO1 is known to form a ring that corrals COPII coats, and we show here how this ring or fence is assembled. Our data reveal that a TANGO1 ring is organized by its radial interaction with COPII, and lateral interactions with cTAGE5, TANGO1-short or itself. Of particular interest is the finding that TANGO1 recruits ERGIC membranes for collagen export via the NRZ (NBAS/RINT1/ZW10) tether complex. Therefore, TANGO1 couples retrograde membrane flow to anterograde cargo transport. Without the NRZ complex, the TANGO1 ring does not assemble, suggesting its role in nucleating or stabilising this process. Thus, coordinated capture of COPII coats, cTAGE5, TANGO1-short, and tethers by TANGO1 assembles a collagen export machine at the ER.
Subject(s)
Antigens, Neoplasm/genetics , Aryl Hydrocarbon Receptor Nuclear Translocator/genetics , Endoplasmic Reticulum/genetics , Neoplasm Proteins/genetics , Protein Transport/genetics , Antigens, Neoplasm/chemistry , Aryl Hydrocarbon Receptor Nuclear Translocator/chemistry , COP-Coated Vesicles/chemistry , COP-Coated Vesicles/genetics , Cell Cycle Proteins/chemistry , Cell Cycle Proteins/genetics , Chromosomal Proteins, Non-Histone/chemistry , Chromosomal Proteins, Non-Histone/genetics , Collagen/chemistry , Collagen/genetics , Collagen/metabolism , Endoplasmic Reticulum/chemistry , Golgi Apparatus/chemistry , Golgi Apparatus/genetics , HeLa Cells , Humans , Microtubule-Associated Proteins/chemistry , Microtubule-Associated Proteins/genetics , Neoplasm Proteins/chemistryABSTRACT
TANGO1 binds and exports Procollagen VII from the endoplasmic reticulum (ER). In this study, we report a connection between the cytoplasmic domain of TANGO1 and SLY1, a protein that is required for membrane fusion. Knockdown of SLY1 by siRNA arrested Procollagen VII in the ER without affecting the recruitment of COPII components, general protein secretion, and retrograde transport of the KDEL-containing protein BIP, and ERGIC53. SLY1 is known to interact with the ER-specific SNARE proteins Syntaxin 17 and 18, however only Syntaxin 18 was required for Procollagen VII export. Neither SLY1 nor Syntaxin 18 was required for the export of the equally bulky Procollagen I from the ER. Altogether, these findings reveal the sorting of bulky collagen family members by TANGO1 at the ER and highlight the existence of different export pathways for secretory cargoes one of which is mediated by the specific SNARE complex containing SLY1 and Syntaxin 18.DOI: http://dx.doi.org/10.7554/eLife.02784.001.
