The SPRY domain-containing SOCS box protein SPSB2 targets iNOS for proteasomal degradation.
Inducible nitric oxide (NO) synthase (iNOS; NOS2) produces NO and related reactive nitrogen species, which are critical effectors of the innate host response and are required for the intracellular killing of pathogens such as Mycobacterium tuberculosis and Leishmania major. We have identified SPRY domain-containing SOCS (suppressor of cytokine signaling) box protein 2 (SPSB2) as a novel negative regulator that recruits an E3 ubiquitin ligase complex to polyubiquitinate iNOS, resulting in its proteasomal degradation. SPSB2 interacts with the N-terminal region of iNOS via a binding interface on SPSB2 that has been mapped by nuclear magnetic resonance spectroscopy and mutational analyses. SPSB2-deficient macrophages showed prolonged iNOS expression, resulting in a corresponding increase in NO production and enhanced killing of L. major parasites. These results lay the foundation for the development of small molecule inhibitors that could disrupt the SPSB-iNOS interaction and thus prolong the intracellular lifetime of iNOS, which may be beneficial in chronic and persistent infections.
Kuang
Zhihe
Z
The Walter and Eliza Hall Institute of Medical Research, Parkville 3052, Victoria, Australia.
Lewis
Rowena S
RS
Curtis
Joan M
JM
Zhan
Yifan
Y
Saunders
Bernadette M
BM
Babon
Jeffrey J
JJ
Kolesnik
Tatiana B
TB
Low
Andrew
A
Masters
Seth L
SL
Willson
Tracy A
TA
Kedzierski
Lukasz
L
Yao
Shenggen
S
Handman
Emanuela
E
Norton
Raymond S
RS
Nicholson
Sandra E
SE
D000818:Animals; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic / Q000235:genetics; D018320:Leishmania major; D016773:Leishmaniasis, Cutaneous / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism*; D008264:Macrophages / Q000378:metabolism* / Q000469:parasitology; D051379:Mice; D018345:Mice, Knockout; D009169:Mycobacterium tuberculosis; D052247:Nitric Oxide Synthase Type II / Q000235:genetics / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D050826:Suppressor of Cytokine Signaling Proteins / Q000235:genetics / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism; D054875:Ubiquitination / Q000235:genetics
D004268:DNA-Binding Proteins; C508499:SSB-2 protein, mouse; D050826:Suppressor of Cytokine Signaling Proteins; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; D044767:Ubiquitin-Protein Ligases; D046988:Proteasome Endopeptidase Complex