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Biomedical subjects

T McClanahan

Publications and source records attributed to T McClanahan.

At least 19 recordsLinked to original sources
PubMed2001

Involvement of chemokine receptors in breast cancer metastasis.

Breast cancer is characterized by a distinct metastatic pattern involving the regional lymph nodes, bone marrow, lung and liver. Tumour cell migration and metastasis share many similarities with leukocyte trafficking, which is critically regulated by chemokines and their receptors. Here we report that the chemokine receptors CXCR4 and CCR7 are highly expressed in human breast cancer cells, malignant breast tumours and metastases. Their respective ligands CXCL12/SDF-1alpha and CCL21/6Ckine exhibit peak levels of expression in organs representing the first destinations of breast cancer metastasis. In breast cancer cells, signalling through CXCR4 or CCR7 mediates actin polymerization and pseudopodia formation, and subsequently induces chemotactic and invasive responses. In vivo, neutralizing the interactions of CXCL12/CXCR4 significantly impairs metastasis of breast cancer cells to regional lymph nodes and lung. Malignant melanoma, which has a similar metastatic pattern as breast cancer but also a high incidence of skin metastases, shows high expression levels of CCR10 in addition to CXCR4 and CCR7. Our findings indicate that chemokines and their receptors have a critical role in determining the metastatic destination of tumour cells.

Actins↗
PubMed2000

Identification of a novel chemokine (CCL28), which binds CCR10 (GPR2).

We report the identification and characterization of a novel CC chemokine designated CCL28 and its receptor CCR10, known previously as orphan G-protein-coupled receptor GPR2. Human and mouse CCL28 share 83% identity at the amino acid and 76% at the nucleic acid levels. We also identified the mouse homologues of CCL28 and of CCR10, which map to mouse chromosomes 13 and 11, respectively. CCL28 is expressed in a variety of human and mouse tissues, and it appears to be predominantly produced by epithelial cells. Both human and mouse CCL28 induce calcium mobilization in human and mouse CCR10-expressing transfectants. CCL28 desensitized the calcium mobilization induced in CCR10 transfectants by CCL27, indicating that these chemokines share this new chemokine receptor. In vitro, recombinant human CCL28 displays chemotactic activity for resting CD4 or CD8 T cells.

Amino Acid Sequence↗
PubMed2000

Interplanetary Network Localization of GRB 991208 and the Discovery of its Afterglow.

The extremely energetic ( approximately 10-4 ergs cm-2) gamma-ray burst (GRB) of 1999 December 8 was triangulated to an approximately 14 arcmin2 error box approximately 1.8 days after its arrival at Earth with the third interplanetary network (IPN), which consists of the Ulysses, Near-Earth Asteroid Rendezvous, and Wind spacecraft. Radio observations with the Very Large Array approximately 2.7 days after the burst revealed a bright fading counterpart whose position is consistent with that of an optical transient source with a redshift of 0.707. We present the time history, peak flux, fluence, and refined 1.3 arcmin2 error box of this event and discuss its energetics. This is the first time that a counterpart has been found for a GRB localized only by the IPN.

Journal Article↗
PubMed2000

Retinoic acid early inducible genes define a ligand family for the activating NKG2D receptor in mice.

Here we describe a family of GPI-anchored cell surface proteins that function as ligands for the mouse activating NKG2D receptor. These molecules are encoded by the retinoic acid early inducible (RAE-1) and H60 minor histocompatibility antigen genes on mouse chromosome 10 and show weak homology with MHC class I. Expression of the NKG2D ligands is low or absent on normal, adult tissues; however, they are constitutively expressed on some tumors and upregulated by retinoic acid. Ectopic expression of RAE-1 and H60 confers target susceptibility to NK cell attack. These studies identify a family of ligands for the activating NKG2D receptor on NK and T cells, which may play an important role in innate and adaptive immunity.

Amino Acid Sequence↗
PubMed1998

Leukocystatin, a new Class II cystatin expressed selectively by hematopoietic cells.

We describe a new cystatin in both mice and humans, which we termed leukocystatin. This protein has all the features of a Class II secreted inhibitory cystatin but contains lysine residues in the normally hydrophobic binding regions. As determined by cDNA library Southern blots, this cystatin is expressed selectively in hematopoietic cells, although fine details of the distribution among these cell types differ between the human and mouse mRNAs. In addition, we have determined the genomic organization of mouse leukocystatin, and we found that in contrast to most cystatins, the leukocystatin gene contains three introns. The recombinant proteins corresponding to these cystatins were expressed in Escherichia coli as N-terminal glutathione S-transferase or FLAGTM fusions, and studies showed that they inhibited papain and cathepsin L but with affinities lower than other cystatins. The unique features of leukocystatin suggests that this cystatin plays a role in immune regulation through inhibition of a unique target in the hematopoietic system.

Amino Acid Sequence↗
PubMed1997

CCR6, a CC chemokine receptor that interacts with macrophage inflammatory protein 3alpha and is highly expressed in human dendritic cells.

Dendritic cells initiate immune responses by ferrying antigen from the tissues to the lymphoid organs for presentation to lymphocytes. Little is known about the molecular mechanisms underlying this migratory behavior. We have identified a chemokine receptor which appears to be selectively expressed in human dendritic cells derived from CD34+ cord blood precursors, but not in dendritic cells derived from peripheral blood monocytes. When stably expressed as a recombinant protein in a variety of host cell backgrounds, the receptor shows a strong interaction with only one chemokine among 25 tested: the recently reported CC chemokine macrophage inflammatory protein 3alpha. Thus, we have designated this receptor as the CC chemokine receptor 6. The cloning and characterization of a dendritic cell CC chemokine receptor suggests a role for chemokines in the control of the migration of dendritic cells and the regulation of dendritic cell function in immunity and infection.

Amino Acid Sequence↗
PubMed1997

A dendritic-cell-derived C-C chemokine that preferentially attracts naive T cells.

Dendritic cells form a system of highly efficient antigen-presenting cells. After capturing antigen in the periphery, they migrate to lymphoid organs where they present the antigen to T cells. Their seemingly unique ability to interact with and sensitize naive T cells gives dendritic cells a central role in the initiation of immune responses and allows them to be used in therapeutic strategies against cancer, viral infection and other diseases. How they interact preferentially with naive rather than activated T lymphocytes is still poorly understood. Chemokines direct the transport of white blood cells in immune surveillance. Here we report the identification and characterization of a C-C chemokine (DC-CK1) that is specifically expressed by human dendritic cells at high levels. Tissue distribution analysis demonstrates that dendritic cells present in germinal centres and T-cell areas of secondary lymphoid organs express this chemokine. We show that DC-CK1, in contrast to RANTES, MIP-1alpha and interleukin-8, preferentially attracts naive T cells (CD45RA+). The specific expression of DC-CK1 by dendritic cells at the site of initiation of an immune response, combined with its chemotactic activity for naive T cells, suggests that DC-CK1 has an important rule in the induction of immune responses.

Amino Acid Sequence↗
PubMed1997

Analysis of dendritic cells at the genetic level.

To increase our understanding of dendritic cell (DC) function we have used two approaches to search at the genetic level for molecules which are specifically expressed by these cells. First, we have performed random sequencing of cDNA libraries prepared from DC. Second, we have employed differential display PCR (DD-PCR). DD-PCR is a powerful technique for the identification at the RNA level of molecules which are expressed in a cell type-specific manner. In our study, we have compared RNA from DC with RNA from a panel of leukocyte cell lines. Here we present a summary of our findings using these two approaches, and show that both methods are complementary and can be used to identify molecules that are specific to DC.

Antigen Presentation↗
PubMed1996

Biochemical and genetic characterization of multiple splice variants of the Flt3 ligand.

We have performed a comprehensive analysis of cell lines and tissues to compare and contrast the expression patterns of Flt3 ligand (FL), c-Kit ligand (KL), and macrophage colony-stimulating factor as well as their receptors, Flt3, c-Kit, and c-Fms. The message for FL is unusually ubiquitous, whereas that of its receptor is quite restricted, apparently limiting the function of the ligand to fetal development and early hematopoiesis. We have also sequenced a mouse FL genomic clone, revealing how the three splice variant FL mRNAs that we have isolated arise. The chromosomal location of the FL gene has been mapped, by in situ hybridization, to chromosome 7 in mouse and chromosome 19 in human. Natural FL protein has been purified from a stromal cell line and shown to be a 65 kD nondisulfide-linked homodimeric glycoprotein comprised of 30 kD subunits, each containing 12 kD of N- and O-linked sugars. Pulse-chase experiments show that one of the splice variants (T110) is responsible for producing the bulk of soluble FL, but only after it has first been expressed at the cell surface as a membrane-bound form. The other splice-variant forms produce molecules that are either obligatorily soluble (T169) or membrane-bound but released only very slowly (T118). Finally, even though most cell lines express some amount of FL mRNA, we found that very little FL protein is actually made, with T cells and stromal cells being the major producers. The data suggests that FL plays its roles over very short distances, perhaps requiring cell-cell contact.

Amino Acid Sequence↗
PubMed1996

The mouse Wnt-10B gene isolated from helper T cells is widely expressed and a possible oncogene in BR6 mouse mammary tumorigenesis.

From libraries made from activated mouse T lymphocytes, we have isolated cDNAs encoding Wnt-10B, a new member of the Wnt family of developmental control genes. This protein appears to be the mammalian orthologue of Wnt-10B, first identified in several non-mammalian vertebrates and recently in mouse. The mRNA expression pattern of mouse Wnt-10B indicates that it is induced following activation of helper T cells, but is also expressed in a variety of other tissues and cells of fetal or adult origin. 93 bp at the 5' end of the cDNA clone are identical to sequences previously reported as 3' flanking genomic DNA adjacent to a mouse mammary tumor virus (MMTV) provirus in the MMTV-induced BR6 mammary tumor, W26. Sequence analysis of tumor-derived genomic DNA confirms that the entire Wnt-10B gene is immediately adjacent to the provirus, suggesting that MMTV integration drives transcription of Wnt-10B, possibly contributing to the oncogenic process. Consistent with this idea is the detection of hybrid MMTV-Wnt-10B transcripts in BR6 tumor cells. T cells which produce abundant Wnt-10B mRNA were also found to produce protein.

Amino Acid Sequence↗
PubMed1996

DNAM-1, a novel adhesion molecule involved in the cytolytic function of T lymphocytes.

Intercellular adhesion molecules play an important role in the generation of T lymphocyte-mediated immune responses. Here, we describe a novel accessory molecule, DNAX accessory molecule-1 (DNAM-1), that is constitutively expressed on the majority of peripheral blood T lymphocytes. DNAM-1 is a 65 kDa transmembrane glycoprotein consisting of 318 aa including two immunoglobulin-like domains. Anti-DNAM-1 monoclonal antibody (MAb) inhibits T and NK cell-mediated cytotoxicity against a variety of tumor cell targets and blocks cytokine production by alloantigen-specific T cells. In addition, DNAM-1 is a tyrosine-phosphorylated signal-transducing molecule that participates in primary adhesion during cytotoxic T lymphocyte (CTL)-mediated cytotoxicity.

Amino Acid Sequence↗
PubMed1995

Molecular cloning of NKB1. A natural killer cell receptor for HLA-B allotypes.

The expression of certain MHC class I allotypes by potential target cells can inhibit NK cell-mediated cytotoxicity. We recently identified the NKB1 surface Ag, expressed on T and NK cell subsets, as a putative inhibitory receptor for HLA-B class I molecules possessing the Bw4 serologic epitope. NKB1 is a 70-kDa glycoprotein that after deglycosylation migrates as a 50-kDa protein as determined by SDS-PAGE. A cDNA encoding the NKB1 receptor was cloned from a NKB1+T cell cDNA library by expression in COS-7 cells using the anti-NKB1 mAb DX9. NKB1 is a member of the lg superfamily containing three lg-like domains in the extracellular region and is related to the recently identified family (p58/NKAT) of human NK and T cell surface molecules that appear to function as inhibitory receptors for HLA class I.

Amino Acid Sequence↗
PubMed1995

A new approach to the study of haematopoietic development in the yolk sac and embryoid bodies.

To understand the mechanisms that control the differentiation of uncommitted mesoderm precursors into haematopoietic stem cells (HSCs) and the activation of haematopoiesis, we conducted a study to identify genes expressed at the earliest stages of both in vivo and in vitro haematopoietic development. Our strategy was to utilize Differential Display by means of the Polymerase Chain Reaction (DD-PCR) to compare patterns of gene expression between mRNA populations representing different levels of haematopoietic activity obtained from the mouse embryo, embryoid bodies (EBs) and mouse cell lines. We report the molecular cloning of two groups of genes expressed in the yolk sac: a group of genes expressed in the day-8.5 yolk sac at higher levels than in the day-8.5 embryo proper and up-regulated during EB development, and another group of day-8.5 yolk sac genes not expressed in the day-8.5 embryo proper or in EBs. Specifically, we describe the molecular cloning of the first nucleobase permease gene to be found in vertebrates, yolk sac permease-like molecule 1 (Ysp11). The Ysp11 gene has the unique property of encoding both intracellular, transmembrane and extracellular protein forms, revealing novel aspects of nucleotide metabolism that may be relevant during mammalian development.

Amino Acid Sequence↗
PubMed1994

Ligand for FLT3/FLK2 receptor tyrosine kinase regulates growth of haematopoietic stem cells and is encoded by variant RNAs.

The FLT3/FLK2 receptor tyrosine kinase is closely related to two receptors, c-Kit and c-Fms, which function with their respective ligands, Kit ligand and macrophage colony-stimulating factor to control differentiation of haematopoietic and non-haematopoietic cells. FLT3/FLK2 is thought to be present on haematopoietic stem cells and found in brain, placenta and testis. We have purified to homogeneity and partially sequenced a soluble form of the FLT3/FLK2 ligand produced by mouse thymic stromal cells. We isolated several mouse and human complementary DNAs that encode polypeptides with identical N termini and different C termini. Some variants contain hydrophobic transmembrane segments, suggesting that processing may be required to release soluble ligand. The purified ligand enhances the response of mouse stem cells and a primitive human progenitor cell population to other growth factors such as interleukins IL-3 and IL-6 and to granulocyte-macrophage colony-stimulating factor, and also stimulates fetal thymocytes.

Amino Acid Sequence↗
PubMed1993

Hematopoietic growth factor receptor genes as markers of lineage commitment during in vitro development of hematopoietic cells.

We have used two in vitro models to identify genes whose expression may serve as markers of lineage commitment during the development of hematopoietic stem cells. One system involves the development in vitro of blastocyst-derived embryonic stem cells into embryoid bodies. The second involves culturing of day 3.5 blastocysts in vitro under conditions that support their development into yolk saclike cysts. In both cases, hematopoietic cells arise in a manner that closely mimics the normal process occurring in the yolk sac of the early mouse embryo. We have focused our analysis on the expression of mRNAs for 15 hematopoietic growth factor receptor genes and other genes expressed in a hematopoietic lineage-specific manner. Although some growth factor receptor genes are apparently expressed constitutively during in vitro development, there are several classes of genes that undergo a highly consistent pattern of induction in both model systems. Genes induced early include those encoding the shared beta subunits of the interleukin-3 (IL-3), IL-5, and granulocyte-macrophage colony-stimulating factor (GM-CSF) receptors; those induced at intermediate times include the c-fms, G-CSF receptor, and CD34 genes; and a gene induced late during in vitro development is the IL-7 receptor gene. The defined temporal order for the expression of these genes suggests that they may be useful as markers for multiple stages in the development of different hematopoietic cell lineages during embryogenesis.

Animals↗
PubMed1990

[Changes in systolic and diastolic function of reperfused myocardium after short coronary occlusions in conscious dogs].

Mongrel dogs were chronically implanted with sonomicrometer crystals and a high fidelity tip micromanometer to measure ventricular wall thickness (WT) and left ventricular pressure (LVP), respectively. Two weeks after surgical operation, the left circumflex coronary artery was occluded with a hydraulic occluder for 3 minutes in conscious condition. During reperfusion, the hemodynamic parameters and systolic wall thickening recovered to the normal level quickly, while an abnormal thickening phase during early relaxation (extra phase) appeared in the dWT/dt-WT loop (X-axis = WT, Y-axis = dWT/dt) with its pattern different from that during control and ischemic conditions. This kind of pattern of the loop could be observed during hypoxia and during rapid overfilling of coronary artery. It is supposed that some substances, which may be produced in the ischemic myocardium, induced an extra dilation of coronary artery during reperfusion and a rapid overperfusion in the early relaxation phase of the cardiac cycle, leading to the abnormal pattern in the loop.

Animals↗