Diabetes is a growing health care issue, and prediabetes has been established as a risk factor for type 2 diabetes. Prediabetes is characterized by deregulated glucose control, and elucidating pathways which govern this process is critical. We have identified the wild-type (WT) p53-inducible phosphatase (WIP1) phosphatase as a regulator of glucose homeostasis. Initial characterization of insulin signaling in WIP1 knockout (WIP1(KO)) murine embryo fibroblasts demonstrated reduced insulin-mediated Ak mouse transforming activation. In order to assess the role of WIP1 in glucose homeostasis, we performed metabolic analysis on mice on a low-fat chow diet (LFD) and high fat diet (HFD). We observed increased expression of proinflammatory cytokines in WIP1(KO) murine embryo fibroblasts, and WIP1(KO) mice fed a LFD and a HFD. WIP1(KO) mice exhibited glucose intolerance and insulin intolerance on a LFD and HFD. However, the effects of WIP1 deficiency cause different metabolic defects in mice on a LFD and a HFD. WIP1(KO) mice on a LFD develop hepatic insulin resistance, whereas this is not observed in HFD-fed mice. Mouse body weights and food consumption increase slightly over time in LFD-fed WT and WIP1(KO) mice. Leptin levels are increased in LFD-fed WIP1(KO) mice, compared with WT. In contrast, HFD-fed WIP1(KO) mice are resistant to HFD-induced obesity, have decreased levels of food consumption, and decreased leptin levels compared with HFD-WT mice. WIP1 has been shown to regulate the nuclear factor kappa-light-chain-enhancer of activated B cells pathway, loss of which leads to increased inflammation. We propose that this increased inflammation triggers insulin resistance in WIP1(KO) mice on LFD and HFD.

Immunoproteasomes are known for their involvement in antigen presentation. However, their broad tissue presence and other evidence are indicative of nonimmune functions. We examined a role for immunoproteasomes in cellular responses to the endogenous and environmental carcinogen formaldehyde (FA) that binds to cytosolic and nuclear proteins producing proteotoxic stress and genotoxic DNA-histone crosslinks. We found that immunoproteasomes were important for suppression of a caspase-independent cell death and the long-term survival of FA-treated cells. All major genotoxic responses to FA, including replication inhibition and activation of the transcription factor p53 and the apical ATM and ATR kinases, were unaffected by immunoproteasome inactivity. Immunoproteasome inhibition enhanced activation of the cytosolic protein damage sensor HSF1, elevated levels of K48-polyubiquitinated cytoplasmic proteins and increased depletion of unconjugated ubiquitin. We further found that FA induced the disassembly of 26S immunoproteasomes, but not standard 26S proteasomes, releasing the 20S catalytic immunoproteasome. FA-treated cells also had higher amounts of small activators PA28αβ and PA28γ bound to 20S particles. Our findings highlight the significance of nonnuclear damage in FA injury and reveal a major role for immunoproteasomes in elimination of FA-damaged cytoplasmic proteins through ubiquitin-independent proteolysis.

Neutrophils rely on ß2 integrins, including Mac‐1, to mediate the cell to cell adhesions underlying trafficking events. Integrin mediated adhesiveness depends on ligand binding affinity, which is controlled through intracellular signaling pathways that induce conformational changes in the integrin extracellular domain in a process known as “inside‐out” signaling. In related integrins, binding of Talin‐1 and Kindlin‐3 to cytoplasmic integrin tails is required for these structural rearrangements. As Mac‐1 holds unique functions apart from other integrins, particularly in the etiology of autoimmune disease, the further characterization of Mac‐1 activation is key to gaining an understanding of how integrin affinity is regulated and ultimately how affinity changes promote autoimmune disease states. To investigate the role of Talin‐1 and Kindlin‐3, we employ functional assays and flow cytometry based reporter antibody assays to probe Mac‐1 conformation in human cell lines and transgenic mice. Preliminary studies suggest that in response to G‐protein coupled receptor signaling, both Talin‐1 and Kindlin‐3 are required for complete integrin activation. This contrasts with previous data that indicates Kindlin‐3 is dispensable for LFA‐1 ectodomain extension following P‐selectin glycoprotein ligand‐1 ligation, suggesting that the mechanisms of ß2 integrin activation may differ for divergent signaling pathways. Overall, determining a direct role for Talin‐1 and Kindlin‐3 in Mac‐1 activation may provide a clearer picture of the etiology of chronic inflammation while highlighting the specific structural confirmations that can be therapeutically targeted in order to stunt the severity of autoimmune states.