Natural Killer Cells Degenerate Intact Sensory Afferents following Nerve Injury

Davies, Alexander J.,Kim, Hyoung Woo,Gonzalez-Cano, Rafael,Choi, Jahyang,Back, Seung Keun,Roh, Seung Eon,Johnson, Errin,Gabriac, Melanie,Kim, Mi-Sun,Lee, Jaehee,Lee, Jeong Eun,Kim, Yun Sook,Bae, Yong Cell Press 2019 Cell Vol. No.

<P><B>Summary</B></P> <P>Sensory axons degenerate following separation from their cell body, but partial injury to peripheral nerves may leave the integrity of damaged axons preserved. We show that an endogenous ligand for the natural killer (NK) cell receptor NKG2D, Retinoic Acid Early 1 (RAE1), is re-expressed in adult dorsal root ganglion neurons following peripheral nerve injury, triggering selective degeneration of injured axons. Infiltration of cytotoxic NK cells into the sciatic nerve by extravasation occurs within 3 days following crush injury. Using a combination of genetic cell ablation and cytokine-antibody complex stimulation, we show that NK cell function correlates with loss of sensation due to degeneration of injured afferents and reduced incidence of post-injury hypersensitivity. This neuro-immune mechanism of selective NK cell-mediated degeneration of damaged but intact sensory axons complements Wallerian degeneration and suggests the therapeutic potential of modulating NK cell function to resolve painful neuropathy through the clearance of partially damaged nerves.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Cytotoxic NK cells infiltrate the damaged peripheral nerve within days of injury </LI> <LI> Injured sensory axons express NKG2D ligand RAE1 to signal degeneration by NK cells </LI> <LI> Clearance of damaged axons reduces development of chronic pain after nerve injury </LI> <LI> NK cells complement Wallerian degeneration to aid functional regeneration of PNS </LI> </UL> </P> <P><B>Graphical Abstract</B></P> <P>[DISPLAY OMISSION]</P>

Differentiated Troy⁺ Chief Cells Act as Reserve Stem Cells to Generate All Lineages of the Stomach Epithelium

Stange, Daniel E.,Koo, B.K.,Huch, M.,Sibbel, G.,Basak, O.,Lyubimova, A.,Kujala, P.,Bartfeld, S.,Koster, J.,Geahlen, Jessica H.,Peters, Peter J.,van Es, Johan H.,van de Wetering, M.,Mills, Jason C.,Cle Cell Press ; MIT Press 2013 Cell Vol.155 No.2

Proliferation of the self-renewing epithelium of the gastric corpus occurs almost exclusively in the isthmus of the glands, from where cells migrate bidirectionally toward pit and base. The isthmus is therefore generally viewed as the stem cell zone. We find that the stem cell marker Troy is expressed at the gland base by a small subpopulation of fully differentiated chief cells. By lineage tracing with a Troy-eGFP-ires-CreERT2 allele, single marked chief cells are shown to generate entirely labeled gastric units over periods of months. This phenomenon accelerates upon tissue damage. Troy<SUP>+</SUP> chief cells can be cultured to generate long-lived gastric organoids. Troy marks a specific subset of chief cells that display plasticity in that they are capable of replenishing entire gastric units, essentially serving as quiescent ''reserve'' stem cells. These observations challenge the notion that stem cell hierarchies represent a ''one-way street.''

A Myc Network Accounts for Similarities between Embryonic Stem and Cancer Cell Transcription Programs

Kim, J.,Woo, A.J.,Chu, J.,Snow, J.W.,Fujiwara, Y.,Kim, C.G.,Cantor, A.B.,Orkin, S.H. Cell Press ; MIT Press 2010 Cell Vol.143 No.2

c-Myc (Myc) is an important transcriptional regulator in embryonic stem (ES) cells, somatic cell reprogramming, and cancer. Here, we identify a Myc-centered regulatory network in ES cells by combining protein-protein and protein-DNA interaction studies and show that Myc interacts with the NuA4 complex, a regulator of ES cell identity. In combination with regulatory network information, we define three ES cell modules (Core, Polycomb, and Myc) and show that the modules are functionally separable, illustrating that the overall ES cell transcription program is composed of distinct units. With these modules as an analytical tool, we have reassessed the hypothesis linking an ES cell signature with cancer or cancer stem cells. We find that the Myc module, independent of the Core module, is active in various cancers and predicts cancer outcome. The apparent similarity of cancer and ES cell signatures reflects, in large part, the pervasive nature of Myc regulatory networks.

CD82/KAI1 Maintains the Dormancy of Long-Term Hematopoietic Stem Cells through Interaction with DARC-Expressing Macrophages

Hur, J.,Choi, J.I.,Lee, H.,Nham, P.,Kim, T.W.,Chae, C.W.,Yun, J.Y.,Kang, J.A.,Kang, J.,Lee, S.,Yoon, C.H.,Boo, K.,Ham, S.,Roh, T.Y.,Jun, J.,Lee, H.,Baek, S.,Kim, H.S. Cell Press 2016 Cell stem cell Vol.18 No.4

<P>Hematopoiesis is regulated by crosstalk between long-term repopulating hematopoietic stem cells (LT-HSCs) and supporting niche cells in the bone marrow (BM). Here, we examine the role of CD82/ KAI1 in niche-mediated LT-HSC maintenance. We found that CD82/ KAI1 is expressed predominantly on LT-HSCs and rarely on other hematopoietic stem-progenitor cells (HSPCs). In Cd82 +/-/+/- mice, LTHSCs were selectively lost as they exited from quiescence and differentiated. Mechanistically, CD82based TGF-b1/ Smad3 signaling leads to induction of CDK inhibitors and cell-cycle inhibition. The CD82 binding partner DARC/ CD234 is expressed on macrophages and stabilizes CD82 on LT-HSCs, promoting their quiescence. When DARC + BMmacrophages were ablated, the level of surface CD82 on LT-HSCs decreased, leading to cell-cycle entry, proliferation, and differentiation. A similar interaction appears to be relevant for human HSPCs. Thus, CD82 is a functional surface marker of LT-HSCs that maintains quiescence through interaction with DARC-expressing macrophages in the BM stem cell niche.</P>

Circulating HIV-Specific Interleukin-21⁺CD4⁺ T Cells Represent Peripheral Tfh Cells with Antigen-Dependent Helper Functions

Schultz, Bruce T.,Teigler, Jeffrey E.,Pissani, F.,Oster, Alexander F.,Kranias, G.,Alter, G.,Marovich, M.,Eller, Michael A.,Dittmer, U.,Robb, Merlin L.,Kim, Jerome H.,Michael, Nelson L.,Bolton, D.,Stre Cell Press 2016 Immunity Vol.44 No.1

<P>A central effort in HIV vaccine development is to generate protective broadly neutralizing antibodies, a process dependent on T follicular helper (Tfh) cells. The feasibility of using peripheral blood counterparts of lymph node Tfh cells to assess the immune response and the influence of viral and vaccine antigens on their helper functions remain obscure. We assessed circulating HIV-specific IL-21(+) CD4(+) T cells and showed transcriptional and phenotypic similarities to lymphoid Tfh cells, and hence representing peripheral Tfh (pTfh) cells. pTfh cells were functionally active and B cell helper quality differed depending on antigen specificity. Furthermore, we found higher frequency of pTfh cells in peripheral blood mononuclear cell specimens from the ALVAC+AIDSVAX (RV144) HIV vaccine trial associated with protective antibody responses compared to the non-protective DNA+Ad5 vaccine trial. Together, we identify IL-21(+) CD4(+) T cells as pTfh cells, implicating them as key populations in the generation of vaccine-evoked antibody responses.</P>

Regulation of Poly(A) Tail and Translation during the Somatic Cell Cycle

Park, J.E.,Yi, H.,Kim, Y.,Chang, H.,Kim, V. Cell Press 2016 Molecular Cell Vol.62 No.3

Poly(A) tails are critical for mRNA stability and translation. However, recent studies have challenged this view, showing that poly(A) tail length and translation efficiency are decoupled in non-embryonic cells. Using TAIL-seq and ribosome profiling, we investigate poly(A) tail dynamics and translational control in the somatic cell cycle. We find dramatic changes in poly(A) tail lengths of cell-cycle regulatory genes like CDK1, TOP2A, and FBXO5, explaining their translational repression in M phase. We also find that poly(A) tail length is coupled to translation when the poly(A) tail is <20 nucleotides. However, as most genes have >20 nucleotide poly(A) tails, their translation is regulated mainly via poly(A) tail length-independent mechanisms during the cell cycle. Specifically, we find that terminal oligopyrimidine (TOP) tract-containing transcripts escape global translational suppression in M phase and are actively translated. Our quantitative and comprehensive data provide a revised view of translational control in the somatic cell cycle.

Integrin α5β1 Activates the NLRP3 Inflammasome by Direct Interaction with a Bacterial Surface Protein

Jun, H.K.,Lee, S.H.,Lee, H.R.,Choi, B.K. Cell Press 2012 Immunity Vol.36 No.5

Integrins are cell-surface heterodimeric glycoproteins composed of alpha and beta subunits that mediate cell-cell, cell-extracellular matrix, and cell-pathogen interactions. In this study, we report a specific role of integrin α5β1 in NLRP3 inflammasome activation in macrophages stimulated by Td92, a surface protein of the periodontopathogen, Treponema denticola. The direct interaction of Td92 with the cell membrane integrin α5β1 resulted in ATP release and K<SUP>+</SUP> efflux, which are the main events in NLRP3 activation. This interaction was arginine-glycine-aspartate (RGD)-independent, and Td92 internalization was not required for the activity. An integrin α5β1 antibody and oxATP, an ATP receptor antagonist, inhibited NLRP3 expression, caspase-1 activation, interleukin-1β (IL-1β) secretion, and proIL-1β synthesis, all of which were regulated by NF-κB activation. Therefore, our data has identified the integrin α5β1 as a principal cell membrane receptor for both NLRP3 inflammasome activation and IL-1β transcription by a bacterial protein, which could exaggerate inflammation, a characteristic of periodontitis.

A Mechanogenetic Toolkit for Interrogating Cell Signaling in Space and Time

Seo, Daeha,Southard, Kaden M.,Kim, Ji-wook,Lee, Hyun Jung,Farlow, Justin,Lee, Jung-uk,Litt, David B.,Haas, Thomas,Alivisatos, A. Paul,Cheon, Jinwoo,Gartner, Zev J.,Jun, Young-wook Cell Press 2016 Cell Vol. No.

<P><B>Summary</B></P> <P>Tools capable of imaging and perturbing mechanical signaling pathways with fine spatiotemporal resolution have been elusive, despite their importance in diverse cellular processes. The challenge in developing a mechanogenetic toolkit (i.e., selective and quantitative activation of genetically encoded mechanoreceptors) stems from the fact that many mechanically activated processes are localized in space and time yet additionally require mechanical loading to become activated. To address this challenge, we synthesized magnetoplasmonic nanoparticles that can image, localize, and mechanically load targeted proteins with high spatiotemporal resolution. We demonstrate their utility by investigating the cell-surface activation of two mechanoreceptors: Notch and vascular endothelial cadherin (VE-cadherin). By measuring cellular responses to a spectrum of spatial, chemical, temporal, and mechanical inputs at the single-molecule and single-cell levels, we reveal how spatial segregation and mechanical force cooperate to direct receptor activation dynamics. This generalizable technique can be used to control and understand diverse mechanosensitive processes in cell signaling.</P> <P><B>Video Abstract</B></P> <P>Display Omitted</P> <P><B>Highlights</B></P> <P> <UL> <LI> Development of a mechanogenetic single-cell perturbation approach </LI> <LI> Interrogation of the spatial, chemical, and mechanical responses of Notch receptors </LI> <LI> Identification of the roles of spatial and mechanical cues on VE-cadherin signaling </LI> <LI> Spatiotemporal and quantitative control of single-cell transcription by nanoprobes </LI> </UL> </P> <P><B>Graphical Abstract</B></P> <P>[DISPLAY OMISSION]</P>

Conserved MicroRNA miR-8/miR-200 and Its Target USH/FOG2 Control Growth by Regulating PI3K

Hyun, S.,Lee, J.H.,Jin, H.,Nam, J.,Namkoong, B.,Lee, G.,Chung, J.,Kim, V.N. Cell Press ; MIT Press 2009 Cell Vol.139 No.6

How body size is determined is a long-standing question in biology, yet its regulatory mechanisms remain largely unknown. Here, we find that a conserved microRNA miR-8 and its target, USH, regulate body size in Drosophila. miR-8 null flies are smaller in size and defective in insulin signaling in fat body that is the fly counterpart of liver and adipose tissue. Fat body-specific expression and clonal analyses reveal that miR-8 activates PI3K, thereby promoting fat cell growth cell-autonomously and enhancing organismal growth non-cell-autonomously. Comparative analyses identify USH and its human homolog, FOG2, as the targets of fly miR-8 and human miR-200, respectively. USH/FOG2 inhibits PI3K activity, suppressing cell growth in both flies and humans. FOG2 directly binds to p85α, the regulatory subunit of PI3K, and interferes with the formation of a PI3K complex. Our study identifies two novel regulators of insulin signaling, miR-8/miR-200 and USH/FOG2, and suggests their roles in adolescent growth, aging, and cancer.

Dendritic Cell Expression of the Signaling Molecule TRAF6 Is Critical for Gut Microbiota-Dependent Immune Tolerance

Han, D.,Walsh, Matthew C.,Cejas, Pedro J.,Dang, Nicholas N.,Kim, Youngmi F.,Kim, J.,Charrier-Hisamuddin, L.,Chau, L.,Zhang, Q.,Bittinger, K.,Bushman, Frederic D.,Turka, Laurence A.,Shen, H.,Reizis, B. Cell Press 2013 Immunity Vol.38 No.6

The intracellular signaling molecule TRAF6 is critical for Toll-like receptor (TLR)-mediated activation of dendritic cells (DCs). We now report that DC-specific deletion of TRAF6 (TRAF6ΔDC) resulted, unexpectedly, in loss of mucosal tolerance, characterized by spontaneous development of T helper 2 (Th2) cells in the lamina propria and eosinophilic enteritis and fibrosis in the small intestine. Loss of tolerance required the presence of gut commensal microbiota but was independent of DC-expressed MyD88. Further, TRAF6ΔDC mice exhibited decreased regulatory T (Treg) cell numbers in the small intestine and diminished induction of iTreg cells in response to model antigen. Evidence suggested that this defect was associated with diminished DC expression of interleukin-2 (IL-2). Finally, we demonstrate that aberrant Th2 cell-associated responses in TRAF6ΔDC mice could be mitigated via restoration of Treg cell activity. Collectively, our findings reveal a role for TRAF6 in directing DC maintenance of intestinal immune tolerance through balanced induction of Treg versus Th2 cell immunity.