All Publications


  • Overexpression of CD47 is associated with brain overgrowth and 16p11.2 deletion syndrome. Proceedings of the National Academy of Sciences of the United States of America Li, J., Brickler, T., Banuelos, A., Marjon, K., Shcherbina, A., Banerjee, S., Bian, J., Narayanan, C., Weissman, I. L., Chetty, S. 2021; 118 (15)

    Abstract

    Copy number variation (CNV) at the 16p11.2 locus is associated with neuropsychiatric disorders, such as autism spectrum disorder and schizophrenia. CNVs of the 16p gene can manifest in opposing head sizes. Carriers of 16p11.2 deletion tend to have macrocephaly (or brain enlargement), while those with 16p11.2 duplication frequently have microcephaly. Increases in both gray and white matter volume have been observed in brain imaging studies in 16p11.2 deletion carriers with macrocephaly. Here, we use human induced pluripotent stem cells (hiPSCs) derived from controls and subjects with 16p11.2 deletion and 16p11.2 duplication to understand the underlying mechanisms regulating brain overgrowth. To model both gray and white matter, we differentiated patient-derived iPSCs into neural progenitor cells (NPCs) and oligodendrocyte progenitor cells (OPCs). In both NPCs and OPCs, we show that CD47 (a "don't eat me" signal) is overexpressed in the 16p11.2 deletion carriers contributing to reduced phagocytosis both in vitro and in vivo. Furthermore, 16p11.2 deletion NPCs and OPCs up-regulate cell surface expression of calreticulin (a prophagocytic "eat me" signal) and its binding sites, indicating that these cells should be phagocytosed but fail to be eliminated due to elevations in CD47. Treatment of 16p11.2 deletion NPCs and OPCs with an anti-CD47 antibody to block CD47 restores phagocytosis to control levels. While the CD47 pathway is commonly implicated in cancer progression, we document a role for CD47 in psychiatric disorders associated with brain overgrowth.

    View details for DOI 10.1073/pnas.2005483118

    View details for PubMedID 33833053

  • Overexpression of CD47 is associated with brain overgrowth and 16p11.2 deletion syndrome PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Li, J., Brickler, T., Banuelos, A., Marjon, K., Shcherbina, A., Banerjee, S., Bian, J., Narayanan, C., Weissman, I. L., Chetty, S. 2021; 118 (15)
  • GD2 is a macrophage checkpoint molecule and combined GD2/CD47 blockade results in synergistic effects and tumor clearance in xenograft models of neuroblastoma and osteosarcoma Theruvath, J., Smith, B., Linde, M. H., Sotillo, E., Heitzeneder, S., Marjon, K., Tousley, A., Lattin, J., Banuelos, A., Dhingra, S., Murty, S., Mackall, C. L., Majzner, R. G. AMER ASSOC CANCER RESEARCH. 2020: 35
  • Tetraspanin CD82 drives acute myeloid leukemia chemoresistance by modulating protein kinase C alpha and β1 integrin activation. Oncogene Floren, M., Restrepo Cruz, S., Termini, C. M., Marjon, K. D., Lidke, K. A., Gillette, J. M. 2020; 39 (19): 3910-3925

    Abstract

    A principal challenge in treating acute myeloid leukemia (AML) is chemotherapy refractory disease. As such, there remains a critical need to identify key regulators of chemotherapy resistance in AML. In this study, we demonstrate that the membrane scaffold, CD82, contributes to the chemoresistant phenotype of AML. Using an RNA-seq approach, we identified the increased expression of the tetraspanin family member, CD82, in response to the chemotherapeutic, daunorubicin. Analysis of the TARGET and BEAT AML databases identifies a correlation between CD82 expression and overall survival of AML patients. Moreover, using a combination of cell lines and patient samples, we find that CD82 overexpression results in significantly reduced cell death in response to chemotherapy. Investigation of the mechanism by which CD82 promotes AML survival in response to chemotherapy identified a crucial role for enhanced protein kinase c alpha (PKCα) signaling and downstream activation of the β1 integrin. In addition, analysis of β1 integrin clustering by super-resolution imaging demonstrates that CD82 expression promotes the formation of dense β1 integrin membrane clusters. Lastly, evaluation of survival signaling following daunorubicin treatment identified robust activation of p38 mitogen-activated protein kinase (MAPK) downstream of PKCα and β1 integrin signaling when CD82 is overexpressed. Together, these data propose a mechanism where CD82 promotes chemoresistance by increasing PKCα activation and downstream activation/clustering of β1 integrin, leading to AML cell survival via activation of p38 MAPK. These observations suggest that the CD82-PKCα signaling axis may be a potential therapeutic target for attenuating chemoresistance signaling in AML.

    View details for DOI 10.1038/s41388-020-1261-0

    View details for PubMedID 32203165

    View details for PubMedCentralID PMC7210072

  • An All Antibody Approach for Conditioning Bone Marrow for Hematopoietic Stem Cell Transplantation with Anti-cKIT and Anti-CD47 in Non-Human Primates Marjon, K. D., Chen, J. Y., Duan, J., Choi, T. S., Sompalli, K., Feng, D., Mata, O., Chen, S., Kean, L., Chao, M., Chao, M., Takimoto, C. H., Agoram, B., Dunbar, C. E., Majeti, R., Weissman, I. L., Liu, J., Volkmer, J. AMER SOC HEMATOLOGY. 2019
  • Neutrophil and monocyte kinetics play critical roles in mouse peritoneal adhesion formation. Blood advances Tsai, J. M., Shoham, M., Fernhoff, N. B., George, B. M., Marjon, K. D., McCracken, M. N., Kao, K. S., Sinha, R., Volkmer, A. K., Miyanishi, M., Seita, J., Rinkevich, Y., Weissman, I. L. 2019; 3 (18): 2713–21

    Abstract

    Peritoneal adhesions are pathological fibroses that ensnare organs after abdominal surgery. This dense connective tissue can cause small bowel obstruction, female infertility, and chronic abdominal pain. The pathogenesis of adhesions is a fibrotic response to tissue damage coordinated between mesothelial cells, fibroblasts, and immune cells. We have previously demonstrated that peritoneal adhesions are a consequence of mechanical injury to the mesothelial layer sustained during surgery. Neutrophils are among the first leukocytes involved in the early response to tissue damage. Here, we show that when subjected to mechanical stress, activated mesothelial cells directly recruit neutrophils and monocytes through upregulation of chemokines such as CXCL1 and monocyte chemoattractant protein 1 (MCP-1). We find that neutrophils within the adhesion sites undergo cell death and form neutrophil extracellular traps (NETosis) that contribute to pathogenesis. Conversely, tissue-resident macrophages were profoundly depleted throughout the disease time course. We show that this is distinct from traditional inflammatory kinetics such as after sham surgery or chemically induced peritonitis, and suggest that adhesions result from a primary difference in inflammatory kinetics. We find that transient depletion of circulating neutrophils significantly decreases adhesion burden, and further recruitment of monocytes with thioglycolate or MCP-1 also improves outcomes. Our findings suggest that the combination of neutrophil depletion and monocyte recruitment is sufficient to prevent adhesion formation, thus providing insight for potential clinical interventions.

    View details for DOI 10.1182/bloodadvances.2018024026

    View details for PubMedID 31519647

  • The tetraspanin CD82 regulates bone marrow homing and engraftment of hematopoietic stem and progenitor cells. Molecular biology of the cell Saito-Reis, C. A., Marjon, K. D., Pascetti, E. M., Floren, M., Gillette, J. M. 2018; 29 (24): 2946-2958

    Abstract

    Hematopoietic stem and progenitor cell (HSPC) transplantation represents a treatment option for patients with malignant and nonmalignant hematological diseases. Initial steps in transplantation involve the bone marrow homing and engraftment of peripheral blood-injected HSPCs. In recent work, we identified the tetraspanin CD82 as a potential regulator of HSPC homing to the bone marrow, although its mechanism remains unclear. In the present study, using a CD82 knockout (CD82KO) mouse model, we determined that CD82 modulates HSPC bone marrow maintenance, homing, and engraftment. Bone marrow characterization identified a significant decrease in the number of long-term hematopoietic stem cells in the CD82KO mice, which we linked to cell cycle activation and reduced stem cell quiescence. Additionally, we demonstrate that CD82 deficiency disrupts bone marrow homing and engraftment, with in vitro analysis identifying further defects in migration and cell spreading. Moreover, we find that the CD82KO HSPC homing defect is due at least in part to the hyperactivation of Rac1, as Rac1 inhibition rescues homing capacity. Together, these data provide evidence that CD82 is an important regulator of HSPC bone marrow maintenance, homing, and engraftment and suggest exploiting the CD82 scaffold as a therapeutic target for improved efficacy of stem cell transplants.

    View details for DOI 10.1091/mbc.E18-05-0305

    View details for PubMedID 30133344

    View details for PubMedCentralID PMC6329911

  • Programmed cell removal by calreticulin in tissue homeostasis and cancer NATURE COMMUNICATIONS Feng, M., Marjon, K. D., Zhu, F., Weissman-Tsukamoto, R., Levett, A., Sullivan, K., Kao, K. S., Markovic, M., Bump, P. A., Jackson, H. M., Choi, T. S., Chen, J., Banuelos, A. M., Liu, J., Gip, P., Cheng, L., Wang, D., Weissman, I. L. 2018; 9
  • Where Hematopoietic Stem Cells Live: The Bone Marrow Niche ANTIOXIDANTS & REDOX SIGNALING Szade, K., Gulati, G. S., Chan, C. F., Kao, K. S., Miyanishi, M., Marjon, K. D., Sinha, R., George, B. M., Chen, J. Y., Weissman, I. L. 2018

    Abstract

    Hematopoietic stem cells (HSCs) can sustain the production of blood throughout one's lifetime. However, for proper self-renewal of its own population and differentiation to blood, the HSC requires a specialized microenvironment called the "niche." Recent Advances: Recent studies using novel mouse models have shed new light on the cellular architecture and function of the HSC niche. Here, we review the different cells that constitute the HSC niche and the molecular mechanisms that underlie HSC and niche interaction. We discuss the evidence and potential features that distinguish the HSC niche from other microenvironments in the bone marrow. The relevance of the niche in malignant transformation of the HSCs and harboring cancer metastasis to the bone is also outlined. In addition, we address how the niche may regulate reactive oxygen species levels surrounding the HSCs. Critical Issues and Future Directions: We propose future directions and remaining challenges in investigating the niche of HSCs. We discuss how a better understanding of the HSC niche may help in restoring an aged hematopoietic system, fighting against malignancies, and transplanting purified HSCs safely and effectively into patients. Antioxid. Redox Signal. 00, 000-000.

    View details for PubMedID 29113449

  • Programmed cell removal by calreticulin in tissue homeostasis and cancer. Nature communications Feng, M. n., Marjon, K. D., Zhu, F. n., Weissman-Tsukamoto, R. n., Levett, A. n., Sullivan, K. n., Kao, K. S., Markovic, M. n., Bump, P. A., Jackson, H. M., Choi, T. S., Chen, J. n., Banuelos, A. M., Liu, J. n., Gip, P. n., Cheng, L. n., Wang, D. n., Weissman, I. L. 2018; 9 (1): 3194

    Abstract

    Macrophage-mediated programmed cell removal (PrCR) is a process essential for the clearance of unwanted (damaged, dysfunctional, aged, or harmful) cells. The detection and recognition of appropriate target cells by macrophages is a critical step for successful PrCR, but its molecular mechanisms have not been delineated. Here using the models of tissue turnover, cancer immunosurveillance, and hematopoietic stem cells, we show that unwanted cells such as aging neutrophils and living cancer cells are susceptible to "labeling" by secreted calreticulin (CRT) from macrophages, enabling their clearance through PrCR. Importantly, we identified asialoglycans on the target cells to which CRT binds to regulate PrCR, and the availability of such CRT-binding sites on cancer cells correlated with the prognosis of patients in various malignancies. Our study reveals a general mechanism of target cell recognition by macrophages, which is the key for the removal of unwanted cells by PrCR in physiological and pathophysiological processes.

    View details for PubMedID 30097573

  • Normal and Neoplastic Stem Cells. Cold Spring Harbor symposia on quantitative biology McCracken, M. N., George, B. M., Kao, K. S., Marjon, K. D., Raveh, T., Weissman, I. L. 2017

    Abstract

    A stem cell is broadly defined as a cell that retains the capacity to self-renew, a feature that confers the ability to continuously make identical daughter cells or additional cells that will differentiate into downstream progeny. This highly regulated genetic program to retain "stemness" is under active investigation. Research in our laboratory has explored similarities and differences in embryonic, tissue-specific, and neoplastic stem cells and their terminally differentiated counterparts. In this review, we will focus on the contributions of our laboratory, in particular on the studies that identified the mouse hematopoietic stem cell (HSC) and the human leukemic stem cell. These studies have led to significant improvements in both preclinical and clinical research, including improved clinical bone marrow transplantation protocols, isolation of nonleukemic HSCs, a cancer immunotherapy currently in clinical trials, and development of a HSC reporter mouse. These studies and the current follow-up research by us and others will continue to identify the properties, function, and regulation of both normal and neoplastic stem cells.

    View details for DOI 10.1101/sqb.2016.81.030965

    View details for PubMedID 28416577

  • Chronic lymphocytic leukemia with clinical debut as neurological involvement: a rare phenomenon and the need for better predictive markers. BMC hematology Rojas-Hernandez, C. M., Nemunaitis, J., Marjon, K. D., Bustamante, D., Zhang, Q., Gillette, J. M. 2017; 17: 3-?

    Abstract

    Chronic lymphocytic leukemia (CLL) is the most common leukemia in Western countries. The frequency of symptomatic central nervous system (CNS) involvement is unknown but thought to be a rare phenomenon. Currently there are no known risk factors for CNS involvement.We describe a clinically staged low-risk CLL case that presented with symptomatic CNS involvement and progressed rapidly to death. Evaluation of the surface adhesion molecules identified a markedly altered expression pattern of the integrin, CD49d, and the tetraspanin, CD82, in the index case when compared to similar low-risk CLL cases. We found that the early Rai clinical stage CLL patients showed linear correlation for the co-expression of CD82 and CD49d. In contrast, this unique index case with CNS involvement, which has the same Rai clinical stage, had a significantly lower expression of CD82 and higher expression of CD49d.These data suggest that the expression profile of CD49d and CD82 may represent potential biomarkers for patients with increased propensity of CNS involvement. Moreover, this study illustrates the critical need for a better mechanistic understanding of how specific adhesion proteins regulate the interactions between CLL cells and various tissue sites.

    View details for DOI 10.1186/s12878-017-0073-0

    View details for PubMedID 28174663

    View details for PubMedCentralID PMC5290634

  • Tetraspanin CD82 regulates bone marrow homing of acute myeloid leukemia by modulating the molecular organization of N-cadherin. Oncogene Marjon, K. D., Termini, C. M., Karlen, K. L., Saito-Reis, C., Soria, C. E., Lidke, K. A., Gillette, J. M. 2015

    Abstract

    Communication between acute myeloid leukemia (AML) and the bone marrow microenvironment is known to control disease progression. Therefore, regulation of AML cell trafficking and adhesion to the bone marrow is of significant interest. In this study, we demonstrate that differential expression of the membrane scaffold CD82 modulates the bone marrow homing of AML cells. By combining mutational analysis and super-resolution imaging, we identify membrane protein clustering by CD82 as a regulator of AML cell adhesion and bone marrow homing. Cluster analysis of super-resolution data indicates that N-linked glycosylation and palmitoylation of CD82 are both critical modifications that control the microdomain organization of CD82 as well as the nanoscale clustering of associated adhesion protein, N-cadherin. We demonstrate that the inhibition of CD82 glycosylation increases the molecular packing of N-cadherin and promotes the bone marrow homing of AML cells. In contrast, we find that the inhibition of CD82 palmitoylation disrupts the formation and organization of N-cadherin clusters and significantly diminishes bone marrow trafficking of AML. Taken together, these data establish a mechanism where the membrane organization of CD82, through specific posttranslational modifications, regulates N-cadherin clustering and membrane density, which impacts the in vivo trafficking of AML cells. As such, these observations provide an alternative model for targeting AML where modulation of protein organization within the membrane may be an effective treatment therapy to disrupt the bone marrow homing potential of AML cells.Oncogene advance online publication, 23 November 2015; doi:10.1038/onc.2015.449.

    View details for DOI 10.1038/onc.2015.449

    View details for PubMedID 26592446

  • The membrane scaffold CD82 regulates cell adhesion by altering alpha 4 integrin stability and molecular density MOLECULAR BIOLOGY OF THE CELL Termini, C. M., Cotter, M. L., Marjon, K. D., Buranda, T., Lidke, K. A., Gillette, J. M. 2014; 25 (10): 1560-1573

    Abstract

    Hematopoietic stem/progenitor cell (HSPC) interactions with the bone marrow microenvironment are important for maintaining HSPC self-renewal and differentiation. In recent work, we identified the tetraspanin protein, CD82, as a regulator of HPSC adhesion and homing to the bone marrow, although the mechanism by which CD82 mediated adhesion was unclear. In the present study, we determine that CD82 expression alters cell-matrix adhesion, as well as integrin surface expression. By combining the superresolution microscopy imaging technique, direct stochastic optical reconstruction microscopy, with protein clustering algorithms, we identify a critical role for CD82 in regulating the membrane organization of α4 integrin subunits. Our data demonstrate that CD82 overexpression increases the molecular density of α4 within membrane clusters, thereby increasing cellular adhesion. Furthermore, we find that the tight packing of α4 into membrane clusters depend on CD82 palmitoylation and the presence of α4 integrin ligands. In combination, these results provide unique quantifiable evidence of CD82's contribution to the spatial arrangement of integrins within the plasma membrane and suggest that regulation of integrin density by tetraspanins is a critical component of cell adhesion.

    View details for DOI 10.1091/mbc.E13-11-0660

    View details for Web of Science ID 000339650800003

    View details for PubMedID 24623721

  • Pentraxins and IgA share a binding hot-spot on Fc alpha RI PROTEIN SCIENCE Lu, J., Marjon, K. D., Mold, C., Marnell, L., Du Clos, T. W., Sun, P. 2014; 23 (4): 378-386

    Abstract

    The pentraxins, C-reactive protein (CRP), and serum amyloid P component (SAP) have previously been shown to function as innate opsonins through interactions with Fcγ receptors. The molecular details of these interactions were elucidated by the crystal structure of SAP in complex with FcγRIIA. More recently, pentraxins were shown to bind and activate FcαRI (CD89), the receptor for IgA. Here, we used mutations of the receptor based on a docking model to further examine pentraxin recognition by FcαRI. The solution binding of pentraxins to six FcαRI alanine cluster mutants revealed that mutations Y35A and R82A, on the C-and F-strands of the D1 domain, respectively, markedly reduced receptor binding to CRP and SAP. These residues are in the IgA-binding site of the receptor, and thus, significantly affected receptor binding to IgA. The shared pentraxin and IgA-binding site on FcαRI is further supported by the results of a solution binding competition assay. In addition to the IgA-binding site, pentraxins appear to interact with a broader region of the receptor as the mutation in the C'-strand (R48A/E49A) enhanced pentraxin binding. Unlike Fcγ receptors, the H129A/I130A and R178A mutations on the BC- and FG-loops of D2 domain, respectively, had little effect on FcαRI binding to the pentraxins. In conclusion, our data suggest that the pentraxins recognize a similar site on FcαRI as IgA.

    View details for DOI 10.1002/pro.2419

    View details for Web of Science ID 000333143800005

    View details for PubMedID 24407959

  • Measurement of Intercellular Transfer to Signaling Endosomes ENDOSOME SIGNALING, PT A Marjon, K. D., Gillette, J. M. 2014; 534: 207-221

    Abstract

    Cell-cell communication is essential for an abundance of physiological processes. As such, various mechanisms have evolved to regulate and ensure proper cell-to-cell signaling. Recently, a novel mechanism of cell communication has emerged which involves the physical transfer of proteins, lipids, and nucleic acids between cells. Following this process termed intercellular transfer (ICT), the transferred molecules can signal within recipient cells by entering the endosomal system and trafficking to signaling endosomes. Signaling endosomes can modulate signal localization within the cell as well as the specificity of, and cross talk between, signaling pathways. As such, ICT into signaling endosomes has the potential to modify the signaling profile of the recipient cell. In this chapter, we describe the different methods of ICT as well as how transfer to signaling endosomes can be visualized and quantified.

    View details for DOI 10.1016/B978-0-12-397926-1.00012-3

    View details for Web of Science ID 000331017300012

    View details for PubMedID 24359956

  • Pentraxins and Fc receptors IMMUNOLOGICAL REVIEWS Lu, J., Marjon, K. D., Mold, C., Du Clos, T. W., Sun, P. D. 2012; 250: 230-238

    Abstract

    Pentraxins are innate pattern recognition molecules whose major function is to bind microbial pathogens or cellular debris during infection and inflammation and, by doing so, contribute to the clearance of necrotic cells as well as pathogens through complement activations. Fc receptors are the cellular mediators of antibody functions. Although conceptually separated, both pentraxins and antibodies are important factors in controlling acute and chronic inflammation and infections. In recent years, increasing experimental evidence suggests a direct link between the innate pentraxins and humoral Fc receptors. Specifically, both human and mouse pentraxins recognize major forms of Fc receptors in solution and on cell surfaces with affinities similar to antibodies binding to their low affinity Fc receptors. Like immune complex, pentraxin aggregation and opsonization of pathogen result in Fc receptor and macrophage activation. The recently published crystal structure of human serum amyloid P (SAP) in complex with FcγRIIA further illustrated similarities to antibody recognition. These recent findings implicate a much broader role than complement activation for pentraxins in immunity. This review summarizes the structural and functional work that bridge the innate pentraxins and the adaptive Fc receptor functions. In many ways, pentraxins can be regarded as innate antibodies.

    View details for DOI 10.1111/j.1600-065X.2012.01162.x

    View details for Web of Science ID 000309752300015

    View details for PubMedID 23046133

  • Recognition and functional activation of the human IgA receptor (Fc alpha RI) by C-reactive protein PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Lu, J., Marjon, K. D., Marnell, L. L., Wang, R., Mold, C., Du Clos, T. W., Sun, P. 2011; 108 (12): 4974-4979

    Abstract

    C-reactive protein (CRP) is an important biomarker for inflammatory diseases. However, its role in inflammation beyond complement-mediated pathogen clearance remains poorly defined. We identified the major IgA receptor, FcαRI, as a ligand for pentraxins. CRP recognized FcαRI both in solution and on cells, and the pentraxin binding site on the receptor appears distinct from that recognized by IgA. Further competitive binding and mutational analysis showed that FcαRI bound to the effector face of CRP in a region overlapping with complement C1q and Fcγ receptor (FcγR) binding sites. CRP cross-linking of FcαRI resulted in extracellular signal-regulated kinase (ERK) phosphorylation, cytokine production, and degranulation in FcαRI-transfected RBL cells. In neutrophils, CRP induced FcαRI surface expression, phagocytosis, and TNF-α secretion. The ability of CRP to activate FcαRI defines a function for pentraxins in inflammatory responses involving neutrophils and macrophages. It also highlights the innate aspect of otherwise humoral immunity-associated antibody receptors.

    View details for DOI 10.1073/pnas.1018369108

    View details for Web of Science ID 000288712200055

    View details for PubMedID 21383176

  • Macrophages Activated by C-Reactive Protein through Fc gamma RI Transfer Suppression of Immune Thrombocytopenia JOURNAL OF IMMUNOLOGY Marjon, K. D., Marnell, L. L., Mold, C., Du Clos, T. W. 2009; 182 (3): 1397-1403

    Abstract

    C-reactive protein (CRP) is an acute-phase protein with therapeutic activity in mouse models of systemic lupus erythematosus and other inflammatory and autoimmune diseases. To determine the mechanism by which CRP suppresses immune complex disease, an adoptive transfer system was developed in a model of immune thrombocytopenic purpura (ITP). Injection of 200 microg of CRP 24 h before induction of ITP markedly decreased thrombocytopenia induced by anti-CD41. CRP-treated splenocytes also provided protection from ITP in adoptive transfer. Splenocytes from C57BL/6 mice were treated with 200 microg/ml CRP for 30 min, washed, and injected into mice 24 h before induction of ITP. Injection of 10(6) CRP-treated splenocytes protected mice from thrombocytopenia, as did i.v. Ig-treated but not BSA-treated splenocytes. The suppressive cell induced by CRP was found to be a macrophage by depletion, enrichment, and the use of purified bone marrow-derived macrophages. The induction of protection by CRP-treated cells was dependent on FcRgamma-chain and Syk activation, indicating an activating effect of CRP on the donor cell. Suppression of ITP by CRP-treated splenocytes required Fc gamma RI on the donor cell and Fc gamma RIIb in the recipient mice. These findings suggest that CRP generates suppressive macrophages through Fc gamma RI, which then act through an Fc gamma RIIb-dependent pathway in the recipient to decrease platelet clearance. These results provide insight into the mechanism of CRP regulatory activity in autoimmunity and suggest a potential new therapeutic approach to ITP.

    View details for Web of Science ID 000262842100023

    View details for PubMedID 19155486

  • Structural recognition and functional activation of Fc gamma R by innate pentraxins NATURE Lu, J., Marnell, L. L., Marjon, K. D., Mold, C., Du Clos, T. W., Sun, P. D. 2008; 456 (7224): 989-U86

    Abstract

    Pentraxins are a family of ancient innate immune mediators conserved throughout evolution. The classical pentraxins include serum amyloid P component (SAP) and C-reactive protein, which are two of the acute-phase proteins synthesized in response to infection. Both recognize microbial pathogens and activate the classical complement pathway through C1q (refs 3 and 4). More recently, members of the pentraxin family were found to interact with cell-surface Fcgamma receptors (FcgammaR) and activate leukocyte-mediated phagocytosis. Here we describe the structural mechanism for pentraxin's binding to FcgammaR and its functional activation of FcgammaR-mediated phagocytosis and cytokine secretion. The complex structure between human SAP and FcgammaRIIa reveals a diagonally bound receptor on each SAP pentamer with both D1 and D2 domains of the receptor contacting the ridge helices from two SAP subunits. The 1:1 stoichiometry between SAP and FcgammaRIIa infers the requirement for multivalent pathogen binding for receptor aggregation. Mutational and binding studies show that pentraxins are diverse in their binding specificity for FcgammaR isoforms but conserved in their recognition structure. The shared binding site for SAP and IgG results in competition for FcgammaR binding and the inhibition of immune-complex-mediated phagocytosis by soluble pentraxins. These results establish antibody-like functions for pentraxins in the FcgammaR pathway, suggest an evolutionary overlap between the innate and adaptive immune systems, and have new therapeutic implications for autoimmune diseases.

    View details for DOI 10.1038/nature07468

    View details for Web of Science ID 000261768300054

    View details for PubMedID 19011614

  • Memory-influencing intra-basolateral amygdala drug infusions modulate expression of Arc protein in the hippocampus PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA McIntyre, C. K., Miyashita, T., Setlow, B., Marjon, K. D., Steward, O., Guzowski, J. F., McGaugh, J. L. 2005; 102 (30): 10718-10723

    Abstract

    Activation of beta-adrenoceptors in the basolateral complex of the amygdala (BLA) modulates memory storage processes and long-term potentiation in downstream targets of BLA efferents, including the hippocampus. Here, we show that this activation also increases hippocampal levels of activity-regulated cytoskeletal protein (Arc), an immediate-early gene (also termed Arg 3.1) implicated in hippocampal synaptic plasticity and memory consolidation processes. Infusions of the beta-adrenoreceptor agonist, clenbuterol, into the BLA immediately after training on an inhibitory avoidance task enhanced memory tested 48 h later. The same dose of clenbuterol significantly increased Arc protein levels in the dorsal hippocampus. Additionally, posttraining intra-BLA infusions of a memory-impairing dose of lidocaine significantly reduced Arc protein levels in the dorsal hippocampus. Increases in Arc protein levels were not accompanied by increases in Arc mRNA, suggesting that amygdala modulation of Arc protein and synaptic plasticity in efferent brain regions occurs at a posttranscriptional level. Finally, infusions of Arc antisense oligodeoxynucleotides into the dorsal hippocampus impaired performance of an inhibitory avoidance task, indicating that the changes in Arc protein expression are related to the observed changes in memory performance.

    View details for DOI 10.1073/pnas.0504436102

    View details for Web of Science ID 000230853300056

    View details for PubMedID 16020527