Brain-specific repression of AMPKα1 alleviates pathophysiology in Alzheimer’s model mice

• Text
• PDF

Abstract

AMP-activated protein kinase (AMPK) is a key regulator at the molecular level to maintain energy metabolism homeostasis. Mammalian AMPK is a heterotrimeric complex and its catalytic α subunit exists in two isoforms: AMPKα1 and AMPKα2. Recent studies suggest a role of AMPKα over-activation in AD-associated synaptic failure. However, whether AD-associated dementia can be improved by targeting AMPK remains unclear, and roles of AMPKα isoforms in AD pathophysiology are not understood. Here we showed distinct disruption of hippocampal AMPKα isoform expression patterns in post mortem human AD patients and AD model mice. We further investigated the effects of brain- and isoform-specific AMPKα repression on AD pathophysiology. We found that repression of AMPKα1 alleviated cognitive deficits and synaptic failure displayed in two separate lines of AD model mice. In contrast, AMPKα2 suppression did not alter AD pathophysiology. Using unbiased mass spectrometry-based proteomics analysis, we identified distinct patterns of protein expression associated with specific AMPKα isoform suppression in AD model mice. Further, AD-associated hyper-phosphorylation of eukaryotic elongation factor 2 (eEF2) was blunted with selective AMPKα1 inhibition. Our findings reveal isoform-specific roles of AMPKα in AD pathophysiology, thus providing insights into potential therapeutic strategy for AD and related dementia syndromes.

Authors

Helena R. Zimmermann, Wenzhong Yang, Nicole P. Kasica, Xueyan Zhou, Xin Wang, Brenna C. Beckelman, Jingyun Lee, Cristina M. Furdui, C. Dirk Keene, Tao Ma

Sensory nerves regulate mesenchymal stromal cell lineage commitment by tuning sympathetic tones

• Text
• PDF

Abstract

Sensory nerve was recently identified as being involved in regulation of bone mass accrual. We previously discovered that PGE2 secreted by osteoblastic cells could activate sensory nerve EP4 receptor to promote bone formation by inhibiting sympathetic activity. However, the fundamental units of bone formation are active osteoblasts, which originate from skeletal stem cells. Here, we found that after sensory denervation, knockout of the EP4 receptor in sensory nerves, or knockout of cyclooxygenase-2 (COX2) in osteoblasts could significantly promote adipogenesis and inhibit osteogenesis in adult mice. Furthermore, injection of SW033291 (a small molecule that locally increases PGE2 level) or propranolol (a beta-blocker) significantly promoted osteogenesis and inhibited adipogenesis. This effect of SW033291, but not propranolol, was abolished in conditional EP4 knockout mice under normal conditions or in the bone repair process. We conclude that the PGE2-EP4 sensory nerve axis could regulate skeletal stem cell differentiation in bone marrow of adult mice.

Authors

Bo Hu, Xiao Lv, Hao Chen, Peng Xue, Bo Gao, Xiao Wang, Gehua Zhen, Janet L. Crane, Dayu Pan, Shen Liu, Shuangfei Ni, Panfeng Wu, Weiping Su, Xiaonan Liu, Zemin Ling, Mi Yang, Ruoxian Deng, Yusheng Li, Lei Wang, Ying Zhang, Mei Wan, Zengwu Shao, Huajiang Chen, Wen Yuan, Xu Cao

Complement activated interferon-γ-primed human endothelium transpresents interleukin-15 to CD8+ T cells

• Text
• PDF

Abstract

Alloantibodies in pre-sensitized transplant candidates deposit complement membrane attack complexes (MAC) on graft endothelial cells (ECs), increasing risk of CD8+ T cell-mediated acute rejection. We recently showed (a) human ECs endocytose MAC into Rab5+ endosomes, creating a signaling platform that stabilizes NF-κB–inducing kinase (NIK) protein; (b) endosomal NIK activates both non-canonical NF-κB signaling to synthesize pro-IL-1β and an NLRP3 inflammasome to process and secrete active IL-1β; and (c) IL-1β activates ECs, increasing recruitment and activation of alloreactive effector memory CD4+ T (TEM) cells. Here, we report IFN-γ priming induced nuclear expression of IL-15/IL-15Rα complexes in cultured human ECs and that MAC-induced IL-1β stimulated translocation of IL-15/IL-15Rα complexes to the EC surface in a canonical NF-κB-dependent process, where IL-15/IL-15Rα transpresentation increased activation and maturation of alloreactive CD8+ TEM. Blocking NLRP3 inflammasome assembly, IL-1 receptor or IL-15 on ECs inhibited the augmented CD8+ TEM responses, indicating this pathway was not redundant. Adoptively transferred alloantibody and mouse complement deposition induced IL-15/IL-15Rα expression by human ECs lining human coronary artery grafts in immunodeficient mice and enhanced intimal CD8+ T cell infiltration, which was markedly reduced by inflammasome inhibition, linking alloantibody to acute rejection. Inhibiting MAC signaling may similarly limit other complement-mediated pathologies.

Authors

Catherine B. Xie, Bo Jiang, Lingfeng Qin, George Tellides, Nancy C. Kirkiles-Smith, Dan Jane-wit, Jordan S. Pober

B cell-intrinsic TLR9 expression is protective in murine lupus

• Text
• PDF

Abstract

Toll-like receptor 9 (TLR9) is a regulator of disease pathogenesis in systemic lupus erythematosus (SLE). Why TLR9 represses disease while TLR7 and MyD88 have the opposite effect remains undefined. To begin to address this question, we created two novel alleles to manipulate TLR9 expression, allowing for either selective deletion or overexpression. We used these to test cell type-specific effects of Tlr9 expression on the regulation of SLE pathogenesis. Notably, Tlr9 deficiency in B cells was sufficient to exacerbate nephritis while extinguishing anti-nucleosome antibodies, whereas Tlr9 deficiency in dendritic cells (DCs), plasmacytoid DCs, and neutrophils had no discernable effect on disease. Thus, B cell-specific Tlr9 deficiency unlinked disease from autoantibody production. Critically, B cell-specific Tlr9 overexpression resulted in ameliorated nephritis, opposite of the effect of deleting Tlr9. Our findings highlight the non-redundant role of B cell-expressed TLR9 in regulating lupus and suggests therapeutic potential in modulating and perhaps even enhancing TLR9 signals in B cells.

Authors

Jeremy S. Tilstra, Shinu John, Rachael A. Gordon, Claire Leibler, Michael Kashgarian, Sheldon Bastacky, Kevin M. Nickerson, Mark J. Shlomchik

Semaphorin 3F signaling actively retains neutrophils at sites of inflammation

• Text
• PDF

Abstract

Neutrophilic inflammation is central to disease pathogenesis, e.g. in chronic obstructive pulmonary disease, yet the mechanisms retaining neutrophils within tissues remain poorly understood. With emerging evidence that axon guidance factors can regulate myeloid recruitment and that neutrophils can regulate expression of a class 3 Semaphorin, SEMA3F, we investigated the role of SEMA3F in inflammatory cell retention within inflamed tissues. We observed that neutrophils upregulate SEMA3F in response to pro-inflammatory mediators and following recruitment to the inflamed lung. In both zebrafish tail injury and murine acute lung injury models of neutrophilic inflammation, overexpression of SEMA3F delayed inflammation resolution with slower neutrophil migratory speeds and retention of neutrophils within the tissues. Conversely, constitutive loss of sema3f accelerated egress of neutrophils from the tail injury site in fish, whilst neutrophil specific deletion of Sema3f in mice resulted in more rapid neutrophil transit through the airways, and significantly reduced time to resolution of the neutrophilic response. Study of filamentous- (F-) actin subsequently showed SEMA3F mediated retention is associated with F-actin disassembly. In conclusion, SEMA3F signaling actively regulates neutrophil retention within the injured tissues with consequences for neutrophil clearance and inflammation resolution.

Authors

Tracie Plant, Suttida Eamsamarng, Manuel A. Sanchez-Garcia, Leila Reyes, Stephen A. Renshaw, Patricia Coelho, Ananda S. Mirchandani, Jessie-May Morgan, Felix E. Ellett, Tyler Morrison, Duncan Humphries, Emily R. Watts, Fiona Murphy, Ximena L. Raffo-Iraolagoitia, Ailiang Zhang, Jenna L. Cash, Catherine Loynes, Philip M. Elks, Freek Van Eeden, Leo M. Carlin, Andrew J. W. Furley, Moira K. B. Whyte, Sarah R. Walmsley

c-Rel gain in B cells drives germinal center reactions and autoantibody production

• Text
• PDF

Abstract

Single nucleotide polymorphisms and locus amplification link the NF-κB transcription factor c-Rel to human autoimmune diseases and B cell lymphomas, respectively. However, the functional consequences of enhanced c-Rel levels remain enigmatic. Here, we overexpressed c-Rel specifically in mouse B cells from BAC-transgenic gene loci and demonstrate that c-Rel protein levels linearly dictated expansion of germinal center (GC) B cells and isotype-switched plasma cells. c-Rel expression in B cells of otherwise c-Rel-deficient mice fully rescued terminal B cell differentiation, underscoring its critical B cell-intrinsic roles. Unexpectedly, in GCB cells transcription-independent regulation produced the highest c-Rel protein levels amongst B cell subsets. In c-Rel overexpressing GCB cells this caused enhanced nuclear translocation, a profoundly altered transcriptional program and increased proliferation. Finally, we provide a link between c-Rel gain and autoimmunity by showing that c-Rel overexpression in B cells caused autoantibody production and renal immune complex deposition.

Authors

Maike Kober-Hasslacher, Hyunju Oh-Strauß, Dilip Kumar, Valeria Soberón, Carina Diehl, Maciej Lech, Thomas Engleitner, Eslam Katab, Vanesa Fernandez Saiz, Guido Piontek, Hongwei Li, Björn Menze, Christoph Ziegenhain, Wolfgang Enard, Roland Rad, Jan P. Böttcher, Hans-Joachim Anders, Martina Rudelius, Marc Schmidt-Supprian

Oncogene-independent BCR-like signaling adaptation confers drug resistance in Ph-like ALL

• Text
• PDF

Abstract

Children and adults with Philadelphia chromosome-like B cell acute lymphoblastic leukemia (Ph-like B-ALL) experience high relapse rates despite best-available conventional chemotherapy. Ph-like ALL is driven by genetic alterations that activate constitutive cytokine receptor and kinase signaling, and early-phase trials are investigating the potential of tyrosine kinase inhibitor (TKI) addition to chemotherapy to improve clinical outcomes. However, preclinical studies have shown that JAK or PI3K pathway inhibition is insufficient to eradicate the most common cytokine receptor-like factor 2 (CRLF2)-rearranged Ph-like ALL subset. We thus sought to define additional essential signaling pathways required in Ph-like leukemogenesis for improved therapeutic targeting. Herein, we describe a novel adaptive signaling plasticity of CRLF2-rearranged Ph-like ALL following selective TKI pressure, which occurs in the absence of genetic mutations. Interestingly, we observed that Ph-like ALL cells have activated SRC, ERK and PI3K signaling consistent with activated B-cell receptor (BCR) signaling, although they do not express cell surface mu heavy chain (uHC). Combinatorial targeting of JAK/STAT, PI3K, and ‘BCR-like’ signaling with multiple TKIs and/or dexamethasone prevented this signaling plasticity and induced complete cell death, demonstrating a more optimal and clinically pragmatic therapeutic strategy for CRLF2-rearranged Ph-like ALL.

Authors

Christian Hurtz, Gerald B. Wertheim, Joseph P. Loftus, Daniel Blumenthal, Anne Lehman, Yong Li, Asen Bagashev, Bryan Manning, Katherine D. Cummins, Janis K. Burkhardt, Alexander E. Perl, Martin Carroll, Sarah K. Tasian

E4BP4-mediated inhibition of T follicular helper cells is compromised in autoimmune disease

• Text
• PDF

Abstract

T follicular helper (Tfh) cells are indispensable for the formation of germinal center (GC) reactions, while T follicular regulatory (Tfr) cells inhibit Tfh-mediated GC responses. Aberrant activation of Tfh cells contributes significantly to the pathogenesis of autoimmune diseases, such as systemic lupus erythematosus (SLE). Nonetheless, the molecular mechanisms mitigating excessive Tfh cell differentiation, which in turn trigger autoimmunity, are not fully understood. Herein we demonstrate that the adenovirus E4 promoter-binding protein (E4BP4) mediates a feedback loop and acts as a transcriptional brake to inhibit Tfh cell differentiation. Furthermore, we show that such an immunological mechanism is compromised in patients with SLE. Establishing mice with either conditional knock-out (cKO) or knock-in (cKI) of the E4bp4 gene in T cells reveals that E4BP4 strongly inhibits Tfh cell differentiation. Mechanistically, E4BP4 deregulates Bcl6 transcription by recruiting the repressive epigenetic modifiers HDAC1 and EZH2. E4BP4 phosphorylation site mutants had limited capability with regard to inhibiting Tfh cell differentiation. In SLE, we detected impaired phosphorylation of E4BP4, finding that this compromised transcription factor is positively correlated with disease activity. These findings unveiled molecular mechanisms by which E4BP4 restrains Tfh cell differentiation, whose compromised function is associated with uncontrolled autoimmune reactions in SLE.

Authors

Zijun Wang, Ming Zhao, Jinghua Yin, Limin Liu, Longyuan Hu, Yi Huang, Aiyun Liu, Jiajun Ouyang, Xiaoli Min, Shijia Rao, Wenhui Zhou, Haijing Wu, Akihiko Yoshimura, Qianjin Lu

Longitudinal study reveals HIV-1-infected CD4⁺ T cell dynamics during long-term antiretroviral therapy

• Text
• PDF

Abstract

Proliferation of CD4+ T cells harboring HIV-1 proviruses is a major contributor to viral persistence in people on antiretroviral therapy (ART). To determine whether differential rates of clonal proliferation or HIV-1-specific CTL pressure shape the provirus landscape, we performed the intact proviral DNA assay (IPDA) and obtained 661 near-full length provirus sequences from eight individuals with suppressed viral loads on ART at time points seven years apart. We observed slow decay of intact proviruses but no changes in the proportions of various types of defective proviruses. The proportion of intact proviruses in expanded clones was similar to that of defective proviruses in clones. Intact proviruses observed in clones did not have more escaped CTL epitopes than intact proviruses observed as singlets. Concordantly, total proviruses at later timepoints or observed in clones were not enriched in escaped or unrecognized epitopes. Three individuals with natural control of HIV-1 infection (controllers) on ART, included because controllers have strong HIV-1-specific CTL responses, had a smaller proportion of intact proviruses but a similar distribution of defective provirus types and escaped or unrecognized epitopes as the other individuals. This work suggests that CTL selection does not significantly check clonal proliferation of infected cells or greatly alter the provirus landscape in people on ART.

Authors

Annukka A. R. Antar, Katharine M. Jenike, Sunyoung Jang, Danielle N. Rigau, Daniel B. Reeves, Rebecca Hoh, Melissa R. Krone, Jeanne C. Keruly, Richard D. Moore, Joshua T. Schiffer, Bareng A.S. Nonyane, Frederick M. Hecht, Steven G. Deeks, Janet D. Siliciano, Ya-Chi Ho, Robert F. Siliciano

Atypical cadherin Fat4 orchestrates lymphatic endothelial cell polarity in response to flow

• Text
• PDF

Abstract

The atypical cadherin FAT4 has established roles in regulation of planar cell polarity and Hippo pathway signaling that are cell context dependent. The recent identification of FAT4 mutations in Hennekam syndrome, features of which include lymphedema, lymphangiectasia and mental retardation, uncovered an important role for FAT4 in the lymphatic vasculature. Hennekam syndrome is also caused by mutations in CCBE1 and ADAMTS3, encoding a matrix protein and protease, respectively, that regulate activity of the key pro-lymphangiogenic VEGF-C/VEGFR3 signaling axis by facilitating the proteolytic cleavage and activation of VEGF-C. The fact that FAT4, CCBE1 and ADAMTS3 mutations underlie Hennekam syndrome suggested that all three genes might function in a common pathway. We identified FAT4 as a target gene of GATA2, a key transcriptional regulator of lymphatic vascular development and in particular, lymphatic vessel valve development. Here, we demonstrate that FAT4 functions in a lymphatic endothelial cell autonomous manner to control cell polarity in response to flow and is required for lymphatic vessel morphogenesis throughout development. Our data reveal a crucial role for FAT4 in lymphangiogenesis and shed light on the mechanistic basis by which FAT4 mutations underlie a human lymphedema syndrome.

Authors

Kelly L. Betterman, Drew L. Sutton, Genevieve A. Secker, Jan Kazenwadel, Anna Oszmiana, Lillian Lim, Naoyuki Miura, Lydia Sorokin, Benjamin M. Hogan, Mark L. Kahn, Helen McNeill, Natasha L. Harvey