The molecular mechanism underlying the pathogenesis of the majority of cases of sporadic Alzheimer's disease (AD) is unknown. A history of stroke was found to be associated with development of some AD cases, especially in the presence of vascular risk factors. Reduced cerebral perfusion is a common vascular component among AD risk factors, and hypoxia is a direct consequence of hypoperfusion. Previously we showed that expression of the ␤-site ␤-amyloid precursor protein (APP) cleavage enzyme 1 (BACE1) gene BACE1 is tightly controlled at both the transcriptional and translational levels and that increased BACE1 maturation contributes to the AD pathogenesis in Down's syndrome. Here we have identified a functional hypoxiaresponsive element in the BACE1 gene promoter. Hypoxia up-regulated ␤-secretase cleavage of APP and amyloid-␤ protein (A␤) production by increasing BACE1 gene transcription and expression both in vitro and in vivo. Hypoxia treatment markedly increased A␤ deposition and neuritic plaque formation and potentiated the memory deficit in Swedish mutant APP transgenic mice. Taken together, our results clearly demonstrate that hypoxia can facilitate AD pathogenesis, and they provide a molecular mechanism linking vascular factors to AD. Our study suggests that interventions to improve cerebral perfusion may benefit AD patients.hypoxia-inducible factor 1␣ ͉ amyloid-␤ protein ͉ neuritic plaque ͉ memory deficit ͉ transcription D eposition of amyloid-␤ protein (A␤) in the brain is the hallmark of Alzheimer's disease (AD) pathology (1). A␤, the major component of neuritic plaques, is derived from ␤-amyloid precursor protein (APP) after sequential cleavage by ␤-and ␥-secretase. Early-onset familial AD caused by mutations in APP and in the presenilin 1 and 2 genes accounts for only Ϸ5% of total AD cases. The majority of AD cases are sporadic AD with late onset and have no defined cause. The major risk factors for AD include aging, atherosclerosis, diabetes mellitus, stroke, the ApoE 4 polymorphism, and less education. Recent studies have shown that a history of stroke can increase AD prevalence by Ϸ2-fold among elderly patients (2-6). The risk is highest when stroke is concomitant with atherosclerotic vascular risk factors (7). Patients with stroke or cerebral infarction also show poorer cognitive performance and greater severity of clinical dementia (8). Hypoxia is a direct consequence of hypoperfusion, a common vascular component among the AD risk factors, and may play an important role in AD pathogenesis.Oxygen homeostasis is essential for the development and physiology of an organism. Hypoxia-inducible factor 1 (HIF-1) is the principal molecule regulating oxygen homeostasis (9). HIF-1 is a member of the basic helix-loop-helix transcription factor family, and the basic region of the protein binds specifically to the 5Ј-RCGTG hypoxia-responsive element (HRE) in a gene promoter region. HIF-1 contains an oxygen-regulated expression subunit ␣ (HIF-1␣) and a constitutively expressed subunit ␤ (HIF-1␤) (Arnt). HIF-1␣...

Tissue repair and regenerative medicine address the important medical needs to replace damaged tissue with functional tissue. Most regenerative medicine strategies have focused on delivering biomaterials and cells, yet there is the untapped potential for drug-induced regeneration with good specificity and safety profiles. The Hippo pathway is a key regulator of organ size and regeneration by inhibiting cell proliferation and promoting apoptosis. Kinases MST1 and MST2 (MST1/2), the mammalian Hippo orthologs, are central components of this pathway and are, therefore, strong target candidates for pharmacologically induced tissue regeneration. We report the discovery of a reversible and selective MST1/2 inhibitor, 4-((5,10-dimethyl-6-oxo-6,10-dihydro-5H-pyrimido[5,4-b]thieno[3,2-e][1,4]diazepin-2-yl)amino)benzenesulfonamide (XMU-MP-1), using an enzyme-linked immunosorbent assay-based high-throughput biochemical assay. The cocrystal structure and the structure-activity relationship confirmed that XMU-MP-1 is on-target to MST1/2. XMU-MP-1 blocked MST1/2 kinase activities, thereby activating the downstream effector Yes-associated protein and promoting cell growth. XMU-MP-1 displayed excellent in vivo pharmacokinetics and was able to augment mouse intestinal repair, as well as liver repair and regeneration, in both acute and chronic liver injury mouse models at a dose of 1 to 3 mg/kg via intraperitoneal injection. XMU-MP-1 treatment exhibited substantially greater repopulation rate of human hepatocytes in the Fah-deficient mouse model than in the vehicle-treated control, indicating that XMU-MP-1 treatment might facilitate human liver regeneration. Thus, the pharmacological modulation of MST1/2 kinase activities provides a novel approach to potentiate tissue repair and regeneration, with XMU-MP-1 as the first lead for the development of targeted regenerative therapeutics.

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Summary Mitochondria need to be juxtaposted to phagosomes to synergistically produce ample reactive oxygen species (ROS) in phagocytes for pathogens killing. However, how phagosomes transmit signal to recruit mitochondria remains unclear. Here, we report that the kinases Mst1 and Mst2 function to control ROS production by regulating mitochondrial trafficking and mitochondrion-phagosome juxtaposition. Mst1 and Mst2 activate Rac GTPase to promote Toll-like receptor (TLR)-triggered assembly of the TRAF6-ECSIT complex that is required for mitochondrial recruitment to phagosomes. Inactive forms of Rac, including the human Rac2D57N mutant, disrupt the TRAF6-ECSIT complex by sequestering TRAF6, and severely dampen ROS production and greatly increase susceptibility to bacterial infection. These findings demonstrate the TLR-Mst1-Mst2-Rac signalling axis to be critical for effective phagosome-mitochondrion function and bactericidal activity.

Alzheimer's Disease (AD) is the most common neurodegenerative disorder leading to dementia and its prevalence increases with age. The pathological features of AD are characterized by the beta-amyloid protein (A(beta)) deposits in the core of neuritic plaques and abnormal neurofibrillary tangles in the brain of AD patients. BACE1 is the major beta-secretase to cleave the beta-amyloid precursor protein (APP) to generate A(beta). Oxidative stress has been shown to affect A(beta) generation in the AD pathogenesis and the mechanism of such effect is unknown. In this report we generated a novel promoterless enhanced green fluorescent protein (EGFP) reporter gene cloning vector and cloned a 1.9-kb BACE1 gene promoter fragment in this vector. The BACE1 promoter fragment can efficiently activate EGFP or luciferase gene transcription. Oxidative stress induced by hydrogen peroxide resulted in significant increase in the BACE1 promoter activity. Furthermore, hydrogen peroxide treatment facilitated beta-secretase activity and A(beta) generation. Thus, upregulation of BACE1 transcription by oxidative stress may contribute to the pathogenesis of Alzheimer's disease.

Neuritic plaques in the brains are one of the pathological hallmarks of Alzheimer ' s disease (AD). Amyloid ␤ -protein (A ␤ ), the central component of neuritic plaques, is derived from ␤ -amyloid precursor protein (APP) after ␤ -and ␥ -secretase cleavage. The molecular mechanism underlying the pathogenesis of AD is not yet well defi ned, and there has been no effective treatment for AD. Valproic acid (VPA) is one of the most widely used anticonvulsant and mood-stabilizing agents for treating epilepsy and bipolar disorder. We found that VPA decreased A ␤ production by inhibiting GSK-3 ␤ -mediated ␥ -secretase cleavage of APP both in vitro and in vivo. VPA treatment signifi cantly reduced neuritic plaque formation and improved memory defi cits in transgenic AD model mice. We also found that early application of VPA was important for alleviating memory defi cits of AD model mice. Our study suggests that VPA may be benefi cial in the prevention and treatment of AD.

The amyloid beta protein (Abeta) is derived from beta-amyloid precursor protein (APP). Cleavage of APP by beta-secretase generates a C-terminal fragment (APPCTFbeta or C99), which is subsequently cleaved by gamma-secretase to produce Abeta. BACE (or BACE1), the major beta-secretase involved in cleaving APP, has been identified as a Type 1 membrane-associated aspartyl protease. In this study, we found that treatment with proteasome inhibitors resulted in an increase in APP C99 levels, suggesting that APP processing at the beta-secretase site may be affected by the ubiquitin-proteasome pathway. To investigate whether the degradation of BACE is mediated by the proteasome pathway, cells stably transfected with BACE were treated with lactacystin. We found that BACE protein degradation was inhibited by lactacystin in a time- and dose-dependent manner. Non-proteasome protease inhibitors had no effect on BACE degradation. BACE protein is ubiquitinated. Furthermore, lactacystin increased APP C99 production and Abeta generation. Our data demonstrate that the degradation of BACE proteins and APP processing are regulated by the ubiquitin-proteasome pathway.

An imbalance in the lineages of immunosuppressive regulatory T cells (T cells) and the inflammatory T17 subset of helper T cells leads to the development of autoimmune and/or inflammatory disease. Here we found that TAZ, a coactivator of TEAD transcription factors of Hippo signaling, was expressed under T17 cell-inducing conditions and was required for T17 differentiation and T17 cell-mediated inflammatory diseases. TAZ was a critical co-activator of the T17-defining transcription factor RORγt. In addition, TAZ attenuated T cell development by decreasing acetylation of the T cell master regulator Foxp3 mediated by the histone acetyltransferase Tip60, which targeted Foxp3 for proteasomal degradation. In contrast, under T cell-skewing conditions, TEAD1 expression and sequestration of TAZ from the transcription factors RORγt and Foxp3 promoted T cell differentiation. Furthermore, deficiency in TAZ or overexpression of TEAD1 induced T cell differentiation, whereas expression of a transgene encoding TAZ or activation of TAZ directed T17 cell differentiation. Our results demonstrate a pivotal role for TAZ in regulating the differentiation of T cells and T17 cells.