John E. Coligan, Ph.D.
Receptor Cell Biology Section
4 Memorial Drive, Room 228B
Bethesda, MD 20814
A major focus of my laboratory’s research is defining the role that CD300 family receptors play in regulating the immune response. There are nine CD300 family members in the mouse that contain a single cell-surface immunoglobulin (Ig) domain that signals through associated intracellular activating and/or inhibitory tyrosine-based signaling motifs. They are expressed mainly by myeloid cells, but, in some cases they are expressed by certain lymphoid cells. The activating members gain signaling potential by pairing with adaptors DAP12, DAP10 and/or FcRγ, whereas the inhibitory receptors contain ITIM motifs for interacting with phosphatases.
CD300f contains both types of motifs. Research on CD300 molecules is in its infancy, but our studies indicate that targeting CD300 receptors will have significant clinical value for modulating immune dysfunctions in a variety of inflammatory disorders, such as autoimmune diseases, sepsis, inflammatory bowel disease (IBD), and cancer. No ligands for CD300 receptors were known until we defined the primary ligands for both mouse CD300f and human CD300a as phosphatidylserine (PS) and phosphatidylethanolamine (PE), respectively. In this context, we found that each of these receptors positively or negatively regulates phagocytosis of apoptotic cells (AC) by professional phagocytes, including macrophages (Mϕ) and dendritic cells (DC). Many diseases characterized by impaired resolution of inflammation, including rheumatoid arthritis, IBD, respiratory distress syndrome, and pulmonary fibrosis, have in common defective clearance of AC. Phagocytosis of AC (efferocytosis) prevents AC from becoming necrotic cells, which are a potent source of pro-inflammatory mediators, and also induces anti-inflammatory cytokines (IL-10 and TGF-β) secretion by phagocytes.
Expression of CD300f by Mϕ enhances efferocytosis, a function that we mapped to tyrosine phosphorylation at the binding site for the p85α regulatory subunit of PI3 kinase in its cytoplasmic tail. The phosphorylation of the other four CD300f cytoplasmic tail Tyr residues leads to inhibition of phagocytosis by muting PI3K activation. In accordance with this inhibitory potential, we found that CD300f negatively regulates DC-mediated efferocytosis and that enhanced efferocytosis by DC in CD300f-deficient mice underlies memory T-cell expansion and susceptibility to systemic lupus erythematosus (SLE)-like autoimmune disease. For IBD, we also found that CD300f-expressing Mϕ and DC play critical roles in controlling disease severity and duration. In Cd300f -/- mice, Mϕ displayed reduced efferocytosis, resulting in AC accumulation in the gut mucosa, which correlated with enhanced efferocytosis by DC. This suggests that regulated availability of intracellular signaling molecules in Mϕ versus DC dictate if CD300f ligation generates signals that overall promote or inhibit efferocytosis. In this regard, we are employing mass spectrometric technology to determine the downstream signaling molecules important in regulating efferocytosis. We have also found that CD300f regulates tumor progression and are in the process of determining the mechanistic basis for this. We hypothesize that CD300f is functioning as a checkpoint receptor on DC-regulating antigen presentation to T cells. This has positive implications for controlling the development of autoimmunity as individuals age but has negative implications for controlling tumorigenesis.
Our plans are to develop strategies for inhibiting CD300f function on DC to treat cancers. In the case of CD300b, we found that it recognizes PS and positively regulates efferocytosis through its association with DAP12. Somewhat surprisingly, we discovered that CD300b also binds LPS, which induces direct association of CD300b with the toll-like receptor (TLR)4 receptor complex. This leads to altered LPS-induced signaling by the complex such that wild-type mice are more susceptible to septic shock than CD300b-deficient mice; this discovery of the CD300b/TLR4 complex changes the paradigm of how TLR4 signals, at least for myeloid cells.
We plan to develop strategies for inhibiting CD300b function to treat sepsis. We also found that CD300d recognizes PS and positively regulates efferocytosis through its association with FcRγ; initial studies suggest that it also recognizes TLR3 ligands (poly I:C). This suggests that we may be able to manipulate CD300d function to treat certain viral diseases. In summary, our goals are to understand how CD300s are regulating the immune response and to develop strategies for clinical intervention for the diseases in which CD300 function is playing a role.
The second area of interest in my laboratory is the function of natural killer (NK) cells in human immunodeficiencies. Defective exocytosis of lytic granules (also known as “secretory lysosomes”), leading to inability of NK cells to control the abnormal growth of lymphocytes or macrophages, is associated with serious and life-threatening histiocytic disorders and lysosomal storage diseases, including Chediak–Higashi syndrome, Hermansky-Pudlak syndrome, Griscelli syndrome, and familial hemophagocytic lymphohistiocytosis.
We are defining the processes regulating exocytosis of lytic granules and their relevance for the pathogenesis of several immune disorders with defective NK-cell function. Two proteins, LAMP1 and -2, compose almost 50 percent of proteins on the surface of lysosomes, and the importance of LAMP proteins is evidenced by the fact that mutations of LAMP2 result in Danon disease (a hypertrophic cardiomyopathy and muscular dystrophy). Still, the function of these proteins is very poorly understood, especially in hematopoietic cells. Our results show that LAMP1 is critical for NK-cell cytotoxicity. Mutations in LYST cause Chediak-Higashi syndrome, a lysosome storage disorder with life-threatening immunodeficiency characterized by the presence of giant lysosome-related organelles in many cell types. Despite LYST having been identified almost 20 years ago, its function remains elusive. Our data shows that LYST is essential for the cytolytic function of NK cells by controlling the size, polarization, and secretion of the lytic granules. Our goal is to elucidate factors critical for NK-cell exocytosis and to develop strategies for manipulating the cytolytic machinery to enhance the immunotherapeutic value of NK cells.
Dr. Coligan received his Ph.D. from Indiana University and did postdoctoral research at the City of Hope Research Institute. After two years as an assistant professor at Rockefeller University, he was a founding member of the Laboratory of Immunogenetics. He has served as head of the Biological Resources Branch and Laboratory of Molecular Structure. In 1998, he joined the Laboratory of Allergic Diseases and became chief of the Receptor Cell Biology Section (RCBS). In 2007, this section moved to the Laboratory of Immunogenetics. His current research is focused on regulation of the immune response by CD300 family receptors and elucidating the mechanism of lytic granule exocytosis in NK cells.
- American Association of Immunologists
- Society for Natural Immunity
- American Society for Biochemistry and Molecular Biology
- Current Protocols in Immunology
- Current Protocols in Protein Science
- Frontiers in NK Cell Biology
Lee HN, Tian L, Bouladoux N, Davis J, Quinones M, Belkaid Y, Coligan JE, Krzewski K. Dendritic cells expressing immunoreceptor CD300f are critical for controlling chronic gut inflammation. J Clin Invest. 2017;127(5):1905-1917.
Tian L, Choi SC, Lee HN, Murakami Y, Qi CF, Sengottuvelu M, Voss O, Krzewski K, Coligan JE. Enhanced efferocytosis by dendritic cells underlies memory T-cell expansion and susceptibility to autoimmune disease in CD300f-deficient mice. Cell Death Differ. 2016;23(6):1086-96.
Voss OH, Murakami Y, Pena MY, Lee HN, Tian L, Margulies DH, Street JM, Yuen PS, Qi CF, Krzewski K, Coligan JE. Lipopolysaccharide-Induced CD300b Receptor Binding to Toll-like Receptor 4 Alters Signaling to Drive Cytokine Responses that Enhance Septic Shock. Immunity. 2016;44(6):1365-78.
Tian L, Choi SC, Murakami Y, Allen J, Morse HC 3rd, Qi CF, Krzewski K, Coligan JE. p85α recruitment by the CD300f phosphatidylserine receptor mediates apoptotic cell clearance required for autoimmunity suppression. Nat Commun. 2014;5:3146.
Murakami Y, Tian L, Voss OH, Margulies DH, Krzewski K, Coligan JE. CD300b regulates the phagocytosis of apoptotic cells via phosphatidylserine recognition. Cell Death Differ. 2014;21(11):1746-57.
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This page was last updated on February 15th, 2017