Biology subjects

Dikic, I.

Publications and source records attributed to Dikic, I..

39 records · Page 3Linked to original sources

bioRxiv2019

Molecular recognition of M1-linked ubiquitin chains by native and phosphorylated UBAN domains

Although the Ub-binding domain in ABIN proteins and NEMO (UBAN) is highly conserved, UBAN-containing proteins exhibit different Ub-binding properties, resulting in their diverse biological roles. Post-translational modifications further control UBAN domain specificity for poly-Ub chains. However, precisely, how the UBAN domain structurally confers such functional diversity remains poorly understood. Here we report crystal structures of ABIN-1 alone and in complex with one or two M1-linked di-Ub chains. ABIN-1 UBAN forms a homo-dimer that provides two symmetrical Ub-binding sites on either side of the coiled-coil structure. Moreover, crystal structures of ABIN1 UBAN in complex with di-Ub chains reveal a concentration-dependency of UBAN/di-Ub binding stoichiometry. Analysis of UBAN/M1-linked di-Ub binding characteristics indicates that phosphorylated S473 in OPTN and its corresponding phospho-mimetic residue in ABIN-1 (E484) are essential for high affinity interactions with M1-linked Ub chains. Also, a phospho-mimetic mutation of A303 in NEMO, corresponding to S473 of OPTN, increases binding affinity for M1-linked Ub chains. These findings are in line with the diverse physiological roles of UBAN domains, as phosphorylation of OPTN UBAN is required to enhance its binding to Ub during mitophagy.

biophysics↗

bioRxiv2017

CYRI1-mediated inhibition of RAC1 signalling restricts Salmonella Typhimurium infection

Salmonella presents a global public health concern. Central to Salmonella pathogenicity is an ability to subvert host defence mechanisms through bacterial effectors that target key host proteins implicated in restricting infection. Thus, to gain insight into host-pathogen interactions governing Salmonella infection, a thorough understanding of host defence mechanisms is needed. To tackle this, we performed an in vivo genome-wide ENU mutagenesis screen to uncover novel host defence proteins. Through this screen we identified an uncharacterised protein, which we name CYRI1 (CYFIP-related RAC1 Interacting protein 1) that serves as a Salmonella resistance factor. We show that CYRI1 binds to the small GTPase RAC1 through a conserved domain present in CYFIP proteins, which are known RAC1 effectors that stimulate actin polymerisation. However, unlike CYFIP proteins, CYRI1 negatively regulates RAC1-driven actin cytoskeleton remodelling, thereby attenuating processes such as phagocytosis and cell migration. This, in turn, enables CYRI1 to counteract Salmonella at various stages of infection, including bacterial entry into epithelial cells, internalisation into myeloid-derived phagocytes as well as phagocyte-mediated bacterial dissemination. Together, this outlines a novel host defence mechanism that is crucial for determining bacterial fate.

cell biology↗

bioRxiv2016

Structural and Functional analysis of the GABARAP Interaction Motif (GIM).

Through the canonical LC3 interaction motif (LIR), [W/F/Y]-X1-X2-[I/L/V], protein complexes are recruited to autophagosomes to perform their functions as either autophagy adaptors or receptors. How these adaptors/receptors selectively interact with either LC3 or GABARAP families remains unclear. Herein, we determine the range of selectivity of 30 known core LIR motifs towards LC3s and GABARAPs. From these, we define a GABARAP Interaction Motif (GIM) sequence (W/F-V-X2-V) that the adaptor protein PLEKHM1 tightly conforms to. Using biophysical and structural approaches, we show that the PLEKHM1-LIR is indeed eleven-fold more specific for GABARAP than LC3B. Selective mutation of the X1 and X2 positions either completely abolished the interaction with all LC3 and GABARAPs or increased PLEKHM1-GIM selectivity 20-fold towards LC3B. Finally, we show that conversion of the canonical p62/SQSTM1-LIR into our newly defined GIM, by introducing two valine residues, enhances p62/SQSTM1 interaction with endogenous GABARAP over LC3B. The identification of a GABARAP-specific interaction motif will aid the identification and characterization of the continually expanding array of autophagy receptor and adaptor proteins and their in vivo functions.

biochemistry↗