Go to  Advanced Search

Divergent mechanisms utilized by SOCS3 to mediate IL-10 inhibition of TNF-a and nitric oxide production by macrophages

Show full item record

Files in this item

Files Size Format Description   View
ubc_2005-0302.pdf 9.134Mb Adobe Portable Document Format   View/Open
 
Title: Divergent mechanisms utilized by SOCS3 to mediate IL-10 inhibition of TNF-a and nitric oxide production by macrophages
Author: Qasimi, Pooran
Degree Master of Science - MSc
Program Experimental Medicine
Copyright Date: 2005
Abstract: The cytokine, interleukin-10 (IL-10), inhibits activation o f macrophages by activators such as lipopolysacchride (LPS). However the mechanism by which IL-10 interferes with LPS signalling is still unclear. One well-characterized signalling pathway activated b y IL-10 is that of Stat3 (Signal transducer and activator o f transcription), which is essential for the antiproliferative and anti-inflammatory actions of IL-10 on macrophages. In our search for IL-10- induced, Stat3-regulated genes, we found a candidate belonging to SOCS (suppressor of cytokine signalling) family of negative regulators of cytokine signalling. Using mutant IL-10 receptor and dominant negative Stat3, we show that IL-10 induces SOCS3 message and protein in a Stat3-dependent manner. However mere expression o f SOCS3 protein in macrophages was not sufficient to inhibit TNF-α protein production in response to LPS, suggesting that additional IL-10-induced signals are required. And indeed we find IL-10 stimulation induces phosphorylation of tyrosine 204 o f SOCS3 protein. In order to determine the role o f SOCS3 in IL-10 inhibition of macrophage activation, we derived cell lines from SOCS3⁻[sup /]⁻ and SOCS3⁺[sup /]⁻ mice. SOCS3⁻[sup /]⁻ macrophages respond to LPS in a manner similar to wild-type cells, but IL-10 is less effective in inhibiting LPS-induced TNF-α and NO production in the SOCS3⁻[sup /]⁻ cells as compared to SOCS3⁺[sup /]⁻ macrophages. Reconstitution of SOCS3⁻[sup /]⁻ cells with a wild-type SOCS3 cDNA restored IL-10 responsiveness. In order to determine which SOCS3 domain is important in IL-10 signalling, SOCS3⁻[sup /]⁻ macrophages were reconstituted with various SOCS3 domain mutants. IL-10 required all domains of SOCS3 protein for the inhibition of TNF-α protein expression. However, for inhibition of TNF-α mRNA expression, IL-10 does not seem to require the KIR domain of SOCS3 protein. In contrast, only the two tyrosine residues, 204 and 221, located in the SOCS-box domain are required for IL-10 inhibition of LPS-induced iNOS protein expression and subsequent NO production. These studies demonstrate the importance of SOCS3 protein in the anti-inflammatory action of IL-10 and that inhibition of NO and TNF-α by IL-10 depends on different domains of SOCS3. Characterization of SOCS3 signalling domains and its immediate downstream targets will allow development of therapeutic strategies, which replicate the beneficial anti- inflammatory action of IL-10.
URI: http://hdl.handle.net/2429/16383
Series/Report no. UBC Retrospective Theses Digitization Project [http://www.library.ubc.ca/archives/retro_theses/]

This item appears in the following Collection(s)

Show full item record

All items in cIRcle are protected by copyright, with all rights reserved.

UBC Library
1961 East Mall
Vancouver, B.C.
Canada V6T 1Z1
Tel: 604-822-6375
Fax: 604-822-3893