Selective Protection of an ARF1-GTP Signaling Axis by a Bacterial Scaffold Induces Bidirectional Trafficking Arrest

Abstract

SUMMARY Bidirectional vesicular transport between the endoplasmic reticulum (ER) and Golgi is mediated largely by ARF and Rab GTPases, which orchestrate vesicle fission and fusion, respectively. How their activities are coordinated in order to define the successive steps of the secretory pathway and preserve traffic directionality is not well understood in part due to the scarcity of molecular tools that simultaneously target ARF and Rab signaling. Here, we take advantage of the unique scaffolding properties of E. coli secreted protein G (EspG) to describe the critical role of ARF1/Rab1 spatiotemporal coordination in vesicular transport at the ER-Golgi intermediate compartment. Structural modeling and cellular studies show that EspG induces bidirectional traffic arrest by tethering vesicles through select ARF1-GTP/effector complexes and local inactivation of Rab1. The mechanistic insights presented here establish the effectiveness of a small bacterial catalytic scaffold for studying complex processes and reveal an alternative mechanism of immune regulation by an important human pathogen.

Enterohaemorrhagic E. coli modulates an ARF6:Rab35 signaling axis to prevent recycling endosome maturation during infection

“…Consistent with previous in vitro data [25], EspG was preferentially co-immunoprecipitated with GTP-bound rather than GDP-bound ARF6 (Fig. 2a).…”

STING Activation by Translocation from the ER Is Associated with Infection and Autoinflammatory Disease

“…We showed previously that Nocodazole prevents membrane trafficking beyond ERGIC in a manner analogous to Rab1 inhibition by the VirA homolog EspG (Selyunin et al, 2014). Brefeldin A (BFA) potently inhibits ARF1 GTPase and can therefore be considered ‘IpaJ-like’.…”

“…Microinjection experiments was done as described in (Selyunin et al, 2014). Briefly, microinjections of IpaJΔ50 and VirAΔ26 were performed using a semiautomatic InjectMan NI2 micromanipulator (Eppendorf).…”

Enterohaemorrhagic E scherichia coli inhibits recycling endosome function and trafficking of surface receptors

“…In the same study, EPEC EspG was shown to reduce hGH secretion and IL-8 release. The phenotypes of both VirA and EspG were attributed specifically to Rab1 inactivation and the resultant decrease in ER-Golgi transport (Dong et al ., 2012), and a model of EspG activity has been proposed where EspG interacts with ARF1 at the cis -Golgi membrane and deactivates the local Rab1 population resulting in bidirectional ER-Golgi trafficking arrest (Selyunin et al ., 2014). …”