Gadd45β expression in chondrosarcoma: A pilot study for diagnostic and biological implications in histological grading

<p>Abstract</p> <p>Background</p> <p>Although the diagnosis of chondrosarcoma, especially the distinction between enchondroma and low-grade chondrosarcoma or low-grade chondrosarcoma and high-grade chondrosarcoma, is pathologically difficult, differential diagnosis is very important because the treatment strategies for these diseases are completely different. The grading system is crucial in predicting biologic behavior and prognosis, however, exact pathological grading is difficult using only routine examinations because the criteria of the grading system are not necessarily definitive. Growth arrest and DNA damage-inducible protein 45β (GADD45β) is an essential molecule for chondrocytes during terminal differentiation. In the present study, we investigated the immunohistochemical expression of GADD45β in enchondroma, and chondrosarcoma of histological grades I, II, and III, to clarify the diagnostic significance of GADD45β in pathological grading of chondrosarcoma.</p> <p>Methods</p> <p>Twenty samples (enchondroma = 6, chondrosarcoma grade I = 7, grade II = 6, grade III = 1) were used for immunohistochemical analysis to investigate the expression of GADD45β. Quantitative analysis was performed to compare the number of GADD45β positive cells and pathological grading.</p> <p>Results</p> <p>Over 70% of the cells in enchondromas expressed GADD45β. On the other hand, the expression of GADD45β decreased significantly according to the histological grade of chondrosarcoma (grade I: 45%; grade II: 13.8%; and grade III: 3.8%).</p> <p>Conclusions</p> <p>The association of GADD45β expression and pathological grading of chondrosarcoma in the present study suggests that the immunohistochemical study of GADD45β may be a specific diagnostic parameter for chondrosarcoma cell differentiation.</p

AIRE Functions As an E3 Ubiquitin Ligase

Autoimmune regulator (AIRE) gene mutation is responsible for the development of autoimmune-polyendocrinopathy-candidiasis ectodermal dystrophy, an organ-specific autoimmune disease with monogenic autosomal recessive inheritance. AIRE is predominantly expressed in medullary epithelial cells of the thymus and is considered to play important roles in the establishment of self-tolerance. AIRE contains two plant homeodomain (PHD) domains, and the novel role of PHD as an E3 ubiquitin (Ub) ligase has just emerged. Here we show that the first PHD (PHD1) of AIRE mediates E3 ligase activity. The significance of this finding was underscored by the fact that disease-causing missense mutations in the PHD1 (C311Y and P326Q) abolished its E3 ligase activity. These results add a novel enzymatic function for AIRE and suggest an indispensable role of the Ub proteasome pathway in the establishment of self-tolerance, in which AIRE is involved

March1-dependent modulation of donor MHC II on CD103+ dendritic cells mitigates alloimmunity.

In transplantation, donor dendritic cells (do-DCs) initiate the alloimmune response either by direct interaction with host T cells or by transferring intact donor MHC to host DCs. However, how do-DCs can be targeted for improving allograft survival is still unclear. Here we show CD103+ DCs are the major do-DC subset involved in the acute rejection of murine skin transplants. In the absence of CD103+ do-DCs, less donor MHC-II is carried to host lymph nodes, fewer allogenic T cells are primed and allograft survival is prolonged. Incubation of skin grafts with the anti-inflammatory mycobacterial protein DnaK reduces donor MHC-II on CD103+DCs and prolongs graft survival. This effect is mediated through IL-10-induced March1, which ubiquitinates and decreases MHC-II levels. Importantly, in vitro pre-treatment of human DCs with DnaK reduces their ability to prime alloreactive T cells. Our findings demonstrate a novel therapeutic approach to dampen alloimmunity by targeting donor MHC-II on CD103+DCs

MARCH1 protects the lipid raft and tetraspanin web from MHCII proteotoxicity in dendritic cells

Dendritic cells (DCs) produce major histocompatibility complex II (MHCII) in large amounts to function as professional antigen presenting cells. Paradoxically, DCs also ubiquitinate and degrade MHCII in a constitutive manner. Mice deficient in the MHCII-ubiquitinating enzyme membrane-anchored RING-CH1, or the ubiquitin-acceptor lysine of MHCII, exhibit a substantial reduction in the number of regulatory T (Treg) cells, but the underlying mechanism was unclear. Here we report that ubiquitin-dependent MHCII turnover is critical to maintain homeostasis of lipid rafts and the tetraspanin web in DCs. Lack of MHCII ubiquitination results in the accumulation of excessive quantities of MHCII in the plasma membrane, and the resulting disruption to lipid rafts and the tetraspanin web leads to significant impairment in the ability of DCs to engage and activate thymocytes for Treg cell differentiation. Thus, ubiquitin-dependent MHCII turnover represents a novel quality-control mechanism by which DCs maintain homeostasis of membrane domains that support DC's Treg cell-selecting function

An Excellent Monitoring System for Surface Ubiquitination-Induced Internalization in Mammals

Background. At present, it is difficult to visualize the internalization of surface receptors induced by ubiquitination that is taken place at the plasma membrane in mammals. This problem makes it difficult to reveal molecular basis for ubiquitinationmediated internalization in mammals. Methodology/Principle Findings. In order to overcome it, we have generated T-REx-c-MIR, a novel mammalian Tet-on B cell line using a constitutively active E3 ubiquitin ligase, c-MIR, and its artificial target molecule. By applying the surface biotinylation method to T-REx-c-MIR, we succeeded to monitor the fate of surface target molecules after initiation of ubiquitination process by doxycycline (Dox)-induced c-MIR expression. Target molecules that preexisted at the plasma membrane before induction of c-MIR expression were oligo-ubiquitinated and degraded by Dox-induced c-MIR expression. Dox-induced c-MIR expression initiated rapid internalization of surface target molecules, and blockage of the internalization induced the accumulation of the surface target molecules that were newly ubiquitinated by c-MIR. Inhibition of the surface ubiquitination by down-regulating ubiquitin conjugating enzyme E2 impaired the internalization of target molecules. Finally, a complex of c-MIR and target molecule was detected at the plasma membrane. Conclusions/ Significances. These results demonstrate that in T-REx-c-MIR, surface target molecule is ubiquitinated at the plasma membrane and followed by being internalized from the plasma membrane. Thus, T-REx-c-MIR is a useful experimental tool t

CD83 increases MHC II and CD86 on dendritic cells by opposing IL-10–driven MARCH1-mediated ubiquitination and degradation

By opposing IL-10–driven, MARCH1-mediated ubiquitination and degradation of MHC class II, CD83 may boost the immunogenicity of dendritic cells

Francisella tularensis Elicits IL-10 via a PGE2-Inducible Factor, to Drive Macrophage MARCH1 Expression and Class II Down-Regulation

Francisella tularensis is a bacterial pathogen that uses host-derived PGE2 to subvert the host's adaptive immune responses in multiple ways. Francisella-induced PGE2 acts directly on CD4 T cells to blunt production of IFN-γ. Francisella-induced PGE2 can also elicit production of a >10 kDa soluble host factor termed FTMØSN (F. tularensis macrophage supernatant), which acts on IFN-γ pre-activated MØ to down-regulate MHC class II expression via a ubiquitin-dependent mechanism, blocking antigen presentation to CD4 T cells. Here, we report that FTMØSN-induced down-regulation of MØ class II is the result of the induction of MARCH1, and that MØ expressing MARCH1 “resistant” class II molecules are resistant to FTMØSN-induced class II down-regulation. Since PGE2 can induce IL-10 production and IL-10 is the only reported cytokine able to induce MARCH1 expression in monocytes and dendritic cells, these findings suggested that IL-10 is the active factor in FTMØSN. However, use of IL-10 knockout MØ established that IL-10 is not the active factor in FTMØSN, but rather that Francisella-elicited PGE2 drives production of a >10 kDa host factor distinct from IL-10. This factor then drives MØ IL-10 production to induce MARCH1 expression and the resultant class II down-regulation. Since many human pathogens such as Salmonella typhi, Mycobacterium tuberculosis and Legionella pneumophila also induce production of host PGE2, these results suggest that a yet-to-be-identified PGE2-inducible host factor capable of inducing IL-10 is central to the immune evasion mechanisms of multiple important human pathogens