Diabetes results from an inadequate mass of functional β cells, due to either β cell loss caused by immune assault or the lack of compensation to overcome insulin resistance. Elucidating the mechanisms that regulate β cell mass has important ramifications for fostering β cell regeneration and the treatment of diabetes. We report here that Skp2, a substrate recognition component of Skp1-Cul1-F-box (SCF) ubiquitin ligase, played an essential and specific role in regulating the cellular abundance of p27 and was a critical determinant of β cell proliferation. In Skp2 -/-mice, accumulation of p27 resulted in enlarged polyploid β cells as a result of endoreduplication replacing proliferation. Despite β cell hypertrophy, Skp2 -/-mice exhibited diminished β cell mass, hypoinsulinemia, and glucose intolerance. Increased insulin resistance resulting from diet-induced obesity caused Skp2 -/-mice to become overtly diabetic, because β cell growth in the absence of cell division was insufficient to compensate for increased metabolic demand. These results indicate that the Skp2-mediated degradation pathway regulating the cellular degradation of p27 is essential for establishing β cell mass and to respond to increased metabolic demand associated with insulin resistance. IntroductionIncreasing evidence suggests that variations in insulin demand as a result of physiological and pathological states such as aging, pregnancy, and obesity can lead to adaptive changes in the β cells that include hyperplasia, hypertrophy, and increased insulin synthesis and secretion (1-4). How β cells respond to changing metabolic demands to regulate β cell mass in order to maintain glucose homeostasis is unclear. The inability of the endocrine pancreas to adapt to the changing insulin demand can result in hyperglycemia and development of diabetes mellitus (5-7). Thus, deciphering the mechanisms that regulate the plasticity of β cell mass can be important in developing effective strategies to treat diabetes. Several recent studies have highlighted the role of cell cycle regulators in establishing β cell mass (reviewed in refs. 8-11). These studies indicate that the balance between cyclin D2-Cdk4 complexes (12) that form in response to mitotic signals and cyclin kinase inhibitors that block the activity of cyclin E-Cdk2 complexes regulates β cell proliferation. We have recently shown that quiescent β cells accumulate p27 and that disabling p27 in these cells allows them to divide (13). Thus, the cellular abundance of p27 is a critical determinant of whether a β cell divides or remains quiescent. Furthermore, deletion of p27 ameliorated hyperglycemia in animal models of type 2 diabetes, suggesting that p27 represents a potential new target for treatment of diabetes (14).The cellular abundance of p27 is normally subject to precise regulation by the ubiquitin-mediated proteolytic pathway (15). Covalent attachment of ubiquitin to p27 by ubiquitin ligases signals its destruction by the 26S proteosome. Specificity in proteolysis by the

In this study, we asked whether exposure to different physiologically relevant temperatures (33°C, 37°C, and 39.5°C) could affect subsequent antigen-specific, activation-related events of naive CD8(+) T cells. We observed that temporary exposure of CD62L(hi)CD44(lo) Pmel-1 CD8(+) cells to 39.5°C prior to their antigen-dependent activation with gp100(25-33) peptide-pulsed C57BL/6 splenocytes resulted in a greater percentage of cells, which eventually differentiated into CD62L(lo)CD44(hi) effector cells compared with cells incubated at 33°C and 37°C. However, the proliferation rate of naive CD8(+) T cells was not affected by mild heating. While exploring these effects further, we observed that mild heating of CD8(+) T cells resulted in the reversible clustering of GM1(+) CD-microdomains in the plasma membrane. This could be attributable to a decrease in line tension in the plasma membrane, as we also observed an increase in membrane fluidity at higher temperatures. Importantly, this same clustering phenomenon was observed in CD8(+) T cells isolated from spleen, LNs, and peripheral blood following mild whole-body heating of mice. Further, we observed that mild heating also resulted in the clustering of TCRβ and the CD8 coreceptor but not CD71R. Finally, we observed an enhanced rate of antigen-specific conjugate formation with APCs following mild heating, which could account for the difference in the extent of differentiation. Overall, these novel findings may help us to further understand the impact of physiologically relevant temperature shifts on the regulation of antigen-specific CD8(+) T cell activation and the subsequent generation of effector cells.

MHC genes in the chicken are arranged into two genetically independent clusters located on the same chromosome. These are the classical B system and restriction fragment pattern-Y (Rfp-Y), a second cluster of MHC genes identified recently through DNA hybridization. Because small numbers of MHC class I and class II genes are present in both B and Rfp-Y, the two clusters might be the result of duplication of an entire chromosomal segment. We subcloned, sequenced, and analyzed the expression of two class I loci mapping to Rfp-Y to determine whether Rfp-Y should be considered either as a second, classical MHC or as a region containing specialized MHC-like genes, such as class Ib genes. The Rfp-Y genes are highly similar to each other (93%) and to classical class Ia genes (73% with chicken B class I; 49% with HLA-A). One locus is disrupted and unexpressed. The other, YFV, is widely transcribed and polymorphic. Mature YFV protein associated with β2m arrives on the surface of chicken B (RP9) lymphoma cells expressing YFV as an epitope-tagged transgene. Substitutions in the YFV Ag-binding region (ABR) occur at four of the eight highly conserved residues that are essential for binding of peptide-Ag in the class Ia molecules. Therefore, it is unlikely that Ag is bound in the YFV ABR in the manner typical of class Ia molecules. This ABR specialization indicates that even though YFV is polymorphic and widely transcribed, it is, in fact, a class Ib gene, and Rfp-Y is a region containing MHC genes of specialized function.

Purpose Clinical trials combining hyperthermia with radiation and/or chemotherapy for cancer treatment have resulted in improved overall survival and control of local recurrences. The contribution of thermally enhanced anti-immune function in these effects is of considerable interest, but not understood; studies on the fundamental effects of elevated temperature on immune effector cells are needed. The goal of this study is to investigate the potential of mild hyperthermia to impact tumor antigen-specific (Ag) effector CD8+ T cell functions. Method Pmel-1 Ag-specific CD8+ T cells were exposed to mild hyperthermia and tested for changes in IFN-γ production and cytotoxicity. Additionally, overall plasma membrane organization and the phosphorylation of signaling proteins were also investigated following heat treatment. Results Exposing effector Pmel-1 specific CD8+ T cells to mild hyperthermia (39.5°C) resulted in significantly enhanced Ag-specific IFN-γ production and tumor target cell killing compared to that seen using lower temperatures (33 and 37°C). Further, inhibition of protein synthesis during hyperthermia did not reduce subsequent Ag-induced IFN-γ production by CD8+ T cells. Correlated with these effects, we observed a distinct clustering of GM1+ lipid microdomains at the plasma membrane and enhanced phosphorylation of LAT and PKCθ which may be related to an observed enhancement of Ag-specific effector CD8+ T cell IFN-γ gene transcription following mild hyperthermia. However, mitogen–mediated production of IFN-γ, which bypasses T cell receptor activation with antigen, was not enhanced. Conclusions Antigen-dependent effector T cell activity is enhanced following mild hyperthermia. These effects could potentially occur in patients being treated with thermal therapies. These data also provide support for the use of thermal therapy as an adjuvant for immunotherapies to improve CD8+ effector cell function.

Macrophages are often considered the sentries in innate immunity, sounding early immunological alarms, a function which speeds the response to infection. Compared to the large volume of studies on regulation of macrophage function by pathogens or cytokines, relatively little attention has been devoted to the role of physical parameters such as temperature. Given that temperature is elevated during fever, a long-recognized cardinal feature of inflammation, it is possible that macrophage function is responsive to thermal signals. To explore this idea, we used LPS to model an aseptic endotoxin-induced inflammatory response in BALB/c mice and found that raising mouse body temperature by mild external heat treatment significantly enhances subsequent LPS-induced release of TNF-α into the peritoneal fluid. It also reprograms macrophages, resulting in sustained subsequent responsiveness to LPS, i.e., this treatment reduces “endotoxin tolerance” in vitro and in vivo. At the molecular level, elevating body temperature of mice results in a increase in LPS-induced downstream signaling including enhanced phosphorylation of IKK and IκB, NF-κB nuclear translocation and binding to the TNF-α promoter in macrophages upon secondary stimulation. Mild heat treatment also induces expression of HSP70 and use of HSP70 inhibitors (KNK437 or Pifithrin-µ) largely abrogates the ability of the thermal treatment to enhance TNF-α, suggesting that the induction of HSP70 is important for mediation of thermal effects on macrophage function. Collectively, these results support the idea that there has been integration between the evolution of body temperature regulation and macrophage function that could help to explain the known survival benefits of fever in organisms following infection.