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GIT2 deficiency attenuates concanavalin A-induced hepatitis in mice.

Hao YE, He DF, Yin RH, Chen H, Wang J, Wang SX, Zhan YQ, Ge CH, Li CY, Yu M, Yang XM - FEBS Open Bio (2015)

Bottom Line: G protein-coupled receptor kinase interactor 2 (GIT2) is a signaling scaffold protein involved in regulation of cytoskeletal dynamics and the internalization of G protein-coupled receptors (GPCRs).However, the functions of GIT2 in T cells have not yet been determined.Our results suggested that GIT2 plays an important role in T-cell function in vivo and in vitro.

View Article: PubMed Central - PubMed

Affiliation: Southern Medical University, Guangzhou, Guangdong Province, China ; State Key Laboratory of Proteomics, Beijing Proteome Research Center, Beijing Institute of Radiation Medicine, Beijing 100850, China.

ABSTRACT
G protein-coupled receptor kinase interactor 2 (GIT2) is a signaling scaffold protein involved in regulation of cytoskeletal dynamics and the internalization of G protein-coupled receptors (GPCRs). The short-splice form of GIT2 is expressed in peripheral T cells and thymocytes. However, the functions of GIT2 in T cells have not yet been determined. We show that treatment with Con A in a model of polyclonal T-lymphocyte activation resulted in marked inhibitions in the intrahepatic infiltration of inflammatory cells, cytokine response and acute liver failure in Git2 (-/-) mice. CD4(+) T cells from Git2 (-/-) mice showed significant impairment in proliferation, cytokine production and signal transduction upon TCR-stimulated activation. Our results suggested that GIT2 plays an important role in T-cell function in vivo and in vitro.

No MeSH data available.


Related in: MedlinePlus

The effect of isolated Tregs on proliferation of responder cells. CD4+CD25− responders were labeled with CFSE and cultured alone or with CD4+CD25+ Tregs at a ratio of 2:1 in the presence of 5 μg/ml Con A. Cells were harvested and gated on CD4+CD25− T cells for FACS. Unstimulated, CFSE-labeled cells were used to verify the peak corresponding to the undivided population.
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f0045: The effect of isolated Tregs on proliferation of responder cells. CD4+CD25− responders were labeled with CFSE and cultured alone or with CD4+CD25+ Tregs at a ratio of 2:1 in the presence of 5 μg/ml Con A. Cells were harvested and gated on CD4+CD25− T cells for FACS. Unstimulated, CFSE-labeled cells were used to verify the peak corresponding to the undivided population.

Mentions: CD4+CD25+Foxp3+ regulatory T (Treg) cells have been shown to be implicated in a number of pathologic processes, such as cancers, infectious disease, and autoimmune disease [32,33]. Foxp3 is a critical regulator of Treg development and function which is supported by the fact that the lethal lymphoproliferative autoimmune syndrome observed in Foxp3-deficient mice resulted from a dificienty in CD25+CD4+ Tregs [34]. Furthermore, Foxp3 is currently the most specific and reliable molecular marker for natural Tregs in rodents and human [35,36]. In this study, we demonstrated that the deletion of GIT2 increased the percentage of Tregs in liver and spleen and increased the number of CD4+CD25+Foxp3+ cells in spleen compared with Git2+/+ mice after Con A injection. Consistent with this observation, we clearly showed a significantly elevated level of IL-10, which is one of the downstream effectors induced by Foxp3, in the serum of Git2−/− compared with WT mice. Although the physiological factors and pathways initiating intracellular Foxp3 expression and promoting its immune regulatory characteristics remain poorly understood, recent studies have revealed that disruption of the signaling components of the NF-κB pathway, including NF-κB-inducing kinase (NIK) and TNF receptor-associated factor 6 (Traf6), leads to impairments in regulatory T cell generation [37,38]. It was recently reported that GIT2 may terminate TLR-induced NF-κB and MAPK signaling by recruiting the deubiquitinating enzyme cylindromatosis to inhibit the ubiquitination of TRAF6 [39]. Therefore, the higher number of CD4+CD25+Foxp3+ cells found in the mice lacking Git2 may be due to the loss of negative regulation of Toll-like receptor (TLR)-induced NF-κB signaling. Furthermore, given that impaired Treg suppressive activity is associated with impaired activation of the GIT–PIX–PAK complex [40], it would be important to compare the suppressive activity of Treg from WT versus KO mice in a standard in vitro Treg suppression assay. However, we did not observe the obvious difference in suppressive activity between WT versus KO mice (Fig. 9), the reason of which should be studied further.


GIT2 deficiency attenuates concanavalin A-induced hepatitis in mice.

Hao YE, He DF, Yin RH, Chen H, Wang J, Wang SX, Zhan YQ, Ge CH, Li CY, Yu M, Yang XM - FEBS Open Bio (2015)

The effect of isolated Tregs on proliferation of responder cells. CD4+CD25− responders were labeled with CFSE and cultured alone or with CD4+CD25+ Tregs at a ratio of 2:1 in the presence of 5 μg/ml Con A. Cells were harvested and gated on CD4+CD25− T cells for FACS. Unstimulated, CFSE-labeled cells were used to verify the peak corresponding to the undivided population.
© Copyright Policy - CC BY-NC-ND
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4556731&req=5

f0045: The effect of isolated Tregs on proliferation of responder cells. CD4+CD25− responders were labeled with CFSE and cultured alone or with CD4+CD25+ Tregs at a ratio of 2:1 in the presence of 5 μg/ml Con A. Cells were harvested and gated on CD4+CD25− T cells for FACS. Unstimulated, CFSE-labeled cells were used to verify the peak corresponding to the undivided population.
Mentions: CD4+CD25+Foxp3+ regulatory T (Treg) cells have been shown to be implicated in a number of pathologic processes, such as cancers, infectious disease, and autoimmune disease [32,33]. Foxp3 is a critical regulator of Treg development and function which is supported by the fact that the lethal lymphoproliferative autoimmune syndrome observed in Foxp3-deficient mice resulted from a dificienty in CD25+CD4+ Tregs [34]. Furthermore, Foxp3 is currently the most specific and reliable molecular marker for natural Tregs in rodents and human [35,36]. In this study, we demonstrated that the deletion of GIT2 increased the percentage of Tregs in liver and spleen and increased the number of CD4+CD25+Foxp3+ cells in spleen compared with Git2+/+ mice after Con A injection. Consistent with this observation, we clearly showed a significantly elevated level of IL-10, which is one of the downstream effectors induced by Foxp3, in the serum of Git2−/− compared with WT mice. Although the physiological factors and pathways initiating intracellular Foxp3 expression and promoting its immune regulatory characteristics remain poorly understood, recent studies have revealed that disruption of the signaling components of the NF-κB pathway, including NF-κB-inducing kinase (NIK) and TNF receptor-associated factor 6 (Traf6), leads to impairments in regulatory T cell generation [37,38]. It was recently reported that GIT2 may terminate TLR-induced NF-κB and MAPK signaling by recruiting the deubiquitinating enzyme cylindromatosis to inhibit the ubiquitination of TRAF6 [39]. Therefore, the higher number of CD4+CD25+Foxp3+ cells found in the mice lacking Git2 may be due to the loss of negative regulation of Toll-like receptor (TLR)-induced NF-κB signaling. Furthermore, given that impaired Treg suppressive activity is associated with impaired activation of the GIT–PIX–PAK complex [40], it would be important to compare the suppressive activity of Treg from WT versus KO mice in a standard in vitro Treg suppression assay. However, we did not observe the obvious difference in suppressive activity between WT versus KO mice (Fig. 9), the reason of which should be studied further.

Bottom Line: G protein-coupled receptor kinase interactor 2 (GIT2) is a signaling scaffold protein involved in regulation of cytoskeletal dynamics and the internalization of G protein-coupled receptors (GPCRs).However, the functions of GIT2 in T cells have not yet been determined.Our results suggested that GIT2 plays an important role in T-cell function in vivo and in vitro.

View Article: PubMed Central - PubMed

Affiliation: Southern Medical University, Guangzhou, Guangdong Province, China ; State Key Laboratory of Proteomics, Beijing Proteome Research Center, Beijing Institute of Radiation Medicine, Beijing 100850, China.

ABSTRACT
G protein-coupled receptor kinase interactor 2 (GIT2) is a signaling scaffold protein involved in regulation of cytoskeletal dynamics and the internalization of G protein-coupled receptors (GPCRs). The short-splice form of GIT2 is expressed in peripheral T cells and thymocytes. However, the functions of GIT2 in T cells have not yet been determined. We show that treatment with Con A in a model of polyclonal T-lymphocyte activation resulted in marked inhibitions in the intrahepatic infiltration of inflammatory cells, cytokine response and acute liver failure in Git2 (-/-) mice. CD4(+) T cells from Git2 (-/-) mice showed significant impairment in proliferation, cytokine production and signal transduction upon TCR-stimulated activation. Our results suggested that GIT2 plays an important role in T-cell function in vivo and in vitro.

No MeSH data available.


Related in: MedlinePlus