The innate immunity kinase TAK1 phosphorylates Rab1 on a hotspot for post-translational modifications by host and pathogen

ABSTRACT: TGF-β Activated Kinase 1 (TAK1) is a critical signaling hub responsible for translating antigen binding signals to immune receptors for the activation of the AP-1 and NF-κB master transcriptional programs. Despite its importance, known substrates of TAK1 are limited to kinases of the MAPK and IKK families and include no direct effectors of biochemical processes. Here, we identify over 200 novel substrates of TAK1 using a chemical genetic kinase strategy. We validate phosphorylation of the dynamic switch II region of GTPase Rab1 at T75 to be regulated by TAK1 in vivo. TAK1 preferentially phosphorylates the inactive (GDP-bound) state of Rab1. Phosphorylation of Rab1 disrupts interaction with GDP Dissociation Inhibitor 1 (GDI1), but not GEF or GAP proteins, and is exclusive to membrane localized Rab1, suggesting phosphorylation may stimulate Rab1 activation and membrane association. We found phosphorylation of Rab1 at T75 to be necessary for normal Rab1 mediated ER to Golgi vesicular transport. Previous studies established that the pathogen Legionella pneumophila is capable of hijacking Rab1 function through post-translational modifications of the switch II region. Here, we present the first evidence that Rab1 is regulated by the host in a similar fashion; and that the innate immunity kinase TAK1 and Legionella effectors compete directly to regulate Rab1 by switch II modifications during infection.

INSTRUMENT(S): LTQ Orbitrap Velos

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Cell Culture

SUBMITTER: Rebecca Levin  

LAB HEAD: Kevan Shokat

PROVIDER: PXD004213 | Pride | 2016-07-19

REPOSITORIES: Pride