An N-terminal addressing sequence targets NLRX1 to the mitochondrial matrix

NLRX1 is the only member of the Nod-like receptor (NLR) family that is targeted to the mitochondria, and its overexpression induces the generation of reactive oxygen species (ROS), thus impacting on NFκB- and JNK-dependent signaling cascades. In addition, NLRX1 has been shown to interact with MAVS (also known as IPS-1, VISA and Cardif) at the mitochondrial outer membrane and to modulate antiviral responses. Here we report that NLRX1 has a functional leader sequence and fully translocates to the mitochondrial matrix via a mechanism requiring the mitochondrial inner-membrane potential, ΔΨm. Importantly, we failed to detect NLRX1 at the mitochondrial outer membrane. We also show that the leader sequence of NLRX1 is removed, which generates a mature protein lacking the first 39 amino acids through a maturation process that is common for mitochondrial-matrix proteins. Finally, we identified UQCRC2, a matrix-facing protein of the respiratory chain complex III, as an NLRX1-interacting molecule, thus providing a molecular basis for the role of NLRX1 in ROS generation. These results provide the first identification of a protein belonging to the NLR family that is targeted to the mitochondrial matrix.

[1]  D. Philpott,et al.  The microbial and danger signals that activate Nod-like receptors. , 2008, Cytokine.

[2]  D. Philpott,et al.  NLRX1 is a mitochondrial NOD‐like receptor that amplifies NF‐κB and JNK pathways by inducing reactive oxygen species production , 2008, EMBO reports.

[3]  D. Arnoult.  Apoptosis-associated mitochondrial outer membrane permeabilization assays. , 2008, Methods.

[4]  M. Heise,et al.  NLRX1 is a regulator of mitochondrial antiviral immunity , 2008, Nature.

[5]  J. Eisenbart,et al.  Jcb: Article , 2022 .

[6]  D. Philpott,et al.  Nod-like proteins in immunity, inflammation and disease , 2006, Nature Immunology.

[7]  Michael Karin,et al.  Intracellular pattern recognition receptors in the host response , 2006, Nature.

[8]  S. Akira,et al.  Pathogen Recognition and Innate Immunity , 2006, Cell.

[9]  Zhijian J. Chen,et al.  Identification and Characterization of MAVS, a Mitochondrial Antiviral Signaling Protein that Activates NF-κB and IRF3 , 2005, Cell.

[10]  K. Mihara,et al.  Export of mitochondrial AIF in response to proapoptotic stimuli depends on processing at the intermembrane space , 2005, The EMBO journal.

[11]  L. Gille,et al.  Intracellular generation of reactive oxygen species by mitochondria. , 2005, Biochemical pharmacology.

[12]  M. Ryan,et al.  Translocation of Proteins into Mitochondria , 2001, IUBMB life.

[13]  P. De Camilli,et al.  Recruitment of an alternatively spliced form of synaptojanin 2 to mitochondria by the interaction with the PDZ domain of a mitochondrial outer membrane protein , 1999, The EMBO journal.

[14]  T. A. Link,et al.  Complete structure of the 11-subunit bovine mitochondrial cytochrome bc1 complex. , 1998, Science.

[15]  W. Neupert,et al.  Processing peptidase of Neurospora mitochondria. Two-step cleavage of imported ATPase subunit 9. , 1984, European journal of biochemistry.

[16]  S. Gasser,et al.  The outer membrane of yeast mitochondria: isolation of outside‐out sealed vesicles , 1983, The EMBO journal.

[17]  D. Philpott,et al.  NLRX 1 is a mitochondrial NOD-like receptor that amplifies NFk B and JNK pathways by inducing reactive oxygen species production , 2008 .

[18]  Zhijian J. Chen,et al.  Identification and characterization of MAVS, a mitochondrial antiviral signaling protein that activates NF-kappaB and IRF 3. , 2005, Cell.