The Sushi domain of soluble IL-15 receptor alpha is essential for binding IL-15 and inhibiting inflammatory and allogenic responses in vitro and in vivo.
IL-15 is a pleiotropic cytokine that plays important roles in both innate and adaptive immunity. It is associated with a range of immunopathology, including rheumatoid arthritis and allograft rejection. IL-15 functions through the trimeric IL-15R complex, which consists of a high affinity binding alpha-chain and the common IL-2R beta- and gamma-chains. Characterization of IL-15/IL-15R interactions may facilitate the development of improved IL-15 antagonists for therapeutic interventions. We previously constructed soluble murine IL-15Ralpha (sIL-15Ralpha) by deleting the cytoplasmic and transmembrane domains. To localize the functional domain of IL-15Ralpha, we have now constructed various truncated versions of sIL-15Ralpha. The shortest region retaining IL-15 binding activity is a 65-aa sequence spanning the Sushi domain of IL-15Ralpha. Sushi domains, common motifs in protein-protein interactions, contain four cysteines forming two disulfide bonds in a 1-3 and 2-4 pattern. Amino acid substitution of the first or fourth cysteine in sIL-15Ralpha completely abolished its IL-15 binding activity. This also abrogated the ability of sIL-15Ralpha to neutralize IL-15-induced proinflammatory cytokine production and anti-apoptotic response in vitro. Furthermore, the mutant sIL-15Ralpha lost its ability to inhibit carrageenan-induced local inflammation and allogenic cell-induced T cell proliferation and cytokine production in vivo. Thus, the Sushi domain is critical for the functional activity of sIL-15Ralpha.
Wei Xq
Department of Immunology and Bacteriology and Center of Rheumatic Disease, University of Glasgow, Glasgow, United Kingdom.
Orchardson
M
M
Gracie
J A
JA
Leung
B P
BP
Gao Bm
Guan
H
H
Niedbala
W
W
Paterson
G K
GK
McInnes
I B
IB
Liew
F Y
FY
D000208:Acute Disease; D020816:Amino Acid Motifs / Q000235:genetics / Q000276:immunology*; D000818:Animals; D017209:Apoptosis / Q000235:genetics / Q000276:immunology; D002351:Carrageenan / Q000008:administration & dosage; D004220:Disulfides / Q000378:metabolism; D004487:Edema / Q000276:immunology* / Q000473:pathology / Q000517:prevention & control*; D005260:Female; D007279:Injections, Subcutaneous; D019409:Interleukin-15 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D007519:Isoantigens / Q000008:administration & dosage / Q000276:immunology*; D008213:Lymphocyte Activation / Q000235:genetics / Q000276:immunology; D051379:Mice; D016297:Mutagenesis, Site-Directed; D009336:Necrosis; D011485:Protein Binding / Q000235:genetics / Q000276:immunology; D017434:Protein Structure, Tertiary / Q000235:genetics; D053647:Receptors, Interleukin-15; D015375:Receptors, Interleukin-2 / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D012995:Solubility; D013154:Spleen / Q000166:cytology / Q000637:transplantation; D013601:T-Lymphocytes / Q000166:cytology / Q000276:immunology / Q000473:pathology
D004220:Disulfides; C508025:Il15ra protein, mouse; D019409:Interleukin-15; D007519:Isoantigens; D053647:Receptors, Interleukin-15; D015375:Receptors, Interleukin-2; D002351:Carrageenan