Distinct roles for TANGO1S domains in maintaining ER-Golgi architecture

The endoplasmic reticulum (ER)-Golgi interface is a dynamic trafficking hub maintained in part by TANGO1, a scaffolding protein that coordinates proteins and membranes at ER exit sites (ERES). TANGO1 has two isoforms: TANGO1L, which has a lumenal SH3 domain, and TANGO1S, which lacks this domain but retains the transmembrane and cytoplasmic coiled-coil (CC), TEER, and PRD domains common to both forms. We showed previously that loss of both isoforms disrupts ER-Golgi organization more severely than TANGO1L loss alone, indicating TANGO1S is functional and can compensate. Here we dissect the role of each TANGO1 cytoplasmic domain in maintaining secretory pathway organisation by expressing TANGO1S domain-deletion mutants in TANGO1L-/S-knockout cells. We show that TANGO1 loss causes cis-Golgi vesiculation that cannot be rescued by TANGO1S, suggesting the lumenal domain of TANGO1L is essential in supporting Golgi architecture. Meanwhile, the TEER domain is essential for the organisation of the ER, whilst the TEER, CC2 and PRD domain are required for a defined ERGIC. All constructs partially rescue COPII recruitment. This study represents an advance towards a domain-level resolution of TANGO1S function. Summary statementIn this study we perform rescue experiments in TANGO1 knockout cells to dissect the role of the TANGO1 cytoplasmic domains in maintaining the ER-ERGIC-Golgi continuum.