A cDNA clone inducible in human tonsillar lymphocytes by a tumor promoter codes for a novel protein of the beta-thromboglobulin superfamily

Identification of amino acid residues critical for LD78beta, a variant of human macrophage inflammatory protein-1alpha, binding to CCR5 and inhibition of R5 human immunodeficiency virus type 1 replication

In an attempt to determine which amino acid(s) of LD78beta, a variant of human macrophage inflammatory protein-1alpha, plays a critical role in the interaction with CCR5, we generated six LD78beta variants with an amino acid substituted to Ala at the NH(2) terminus of LD78beta. There was no significant difference in eliciting Ca(2+) flux and chemotaxis among the variants with the exception of LD78beta(T9A) showing a substantially reduced activity. The comparative order for human immunodeficiency virus type 1 (HIV-1) replication inhibition was: LD78beta(P8A) > LD78beta(D6A) > LD78beta(WT), LD78beta(L3A) > LD78beta(T7A), LD78beta(P2A) > LD78beta(T9A). In binding inhibition assays of LD78beta variants using 2D7 monoclonal antibody and (125)I-labeled macrophage inflammatory protein-1alpha, the comparative order was: LD78beta(P8A), LD78beta(D6A) > LD78beta(WT) > LD78beta(L3A) > LD78beta(T7A) > LD78beta(T9A), LD78betaP2A). The order for CCR5 down-regulation induction was comparable to that for binding inhibition. The present data suggest that Pro-2, Asp-6, Pro-8, and Thr-9 are critical for LD78beta binding to CCR5 and HIV-1 replication inhibition, and that LD78beta binding to CCR5, regardless of affinity, is sufficient for the initial signal transduction of LD78beta, whereas the greater anti-HIV-1 activity requires the greater magnitude of binding. The data also suggest that LD78beta variants with appropriate amino acid substitution(s) such as LD78beta(D6A) and LD78beta(P8A) may represent effective chemokine-based anti-HIV-1 therapeutics while preserving LD78beta-CCR5 interactions.

Involvement of both the V2 and V3 regions of the CCR5-tropic human immunodeficiency virus type 1 envelope in reduced sensitivity to macrophage inflammatory protein 1alpha

To determine whether C-C chemokines play an important role in the phenotype switch of human immunodeficiency virus (HIV) from CCR5 to CXCR4 usage during the course of an infection in vivo, macrophage inflammatory protein (MIP)-1alpha-resistant variants were isolated from CCR5-tropic (R5) HIV-1 in vitro. The selected variants displayed reduced sensitivities to MIP-1alpha (fourfold) through CCR5-expressing CD4-HeLa/long terminal repeat-beta-galactosidase (MAGI/CCR5) cells. The variants were also resistant to other natural ligands for CCR5, namely, MIP-1beta (>4-fold) and RANTES (regulated upon activation, normal T-cell expressed and secreted) (6-fold). The env sequence analyses revealed that the variants had amino acid substitutions in V2 (valine 166 to methionine) and V3 (serine 303 to glycine), although the same V3 substitution appeared in virus passaged without MIP-1alpha. A single-round replication assay using a luciferase reporter HIV-1 strain pseudotyped with mutant envelopes confirmed that mutations in both V2 and V3 were necessary to confer the reduced sensitivity to MIP-1alpha, MIP-1beta, and RANTES. However, the double mutant did not switch its chemokine receptor usage from CCR5 to CXCR4, indicating the altered recognition of CCR5 by this mutant. These results indicated that V2 combined with the V3 region of the CCR5-tropic HIV-1 envelope modulates the sensitivity of HIV-1 to C-C chemokines without altering the ability to use chemokine receptors.

Human T-cell lymphotrophic virus type-I tax gene induces secretion of human macrophage inflammatory protein-1alpha

Human T-cell lymphotropic virus I (HTLV-I) encodes for a 40-kDa protein, Tax, which is important for the immortalization of T cells. Tax has been shown to transactivate several cellular genes. In this study, we show that MIP-1alpha is selectively expressed and secreted in the tax transfected Jurkat cell line upon mitogen stimulation. Expression of MIP-1alpha-R mRNA in these cells suggests an autocrine role for this chemokine in HTLV-I infected T-cells. Induced MIP-1alpha expression and secretion in PMA/PHA stimulated tax transfected cells correlate with the noninduction of MNP-1 transcription factor, which is intimately involved in downmodulating the MIP-1alpha gene.

CKβ-11/Macrophage Inflammatory Protein-3β/EBI1-Ligand Chemokine Is an Efficacious Chemoattractant for T and B Cells

We examined the functional properties of CKβ-11/MIP-3β/ELC, a recently reported CC chemokine that specifically binds to a chemokine receptor, EBI1/BLR2/CCR7. CKβ-11/MIP-3β/ELC is distantly related to other CC and CXC chemokines in primary amino acid sequence structure. Recombinant human CKβ-11/MIP-3β/ELC expressed from a mammalian cell system showed potent chemotactic activity for T cells and B cells but not for granulocytes and monocytes. An optimal concentration of CKβ-11/MIP-3β/ELC attracted most input T cells within 3 h, a chemotactic activity comparable with that of stromal cell derived factor 1 (SDF-1), a highly efficacious CXC chemokine. CKβ-11/MIP-3β/ELC equally attracted naive CD45RA+ and memory type CD45RO+ T cells. CKβ-11/MIP-3β/ELC also strongly attracted both CD4+ and CD8+ T cells, but the attraction for CD4+ T cells was greater. CKβ-11/MIP-3β/ELC was also a more efficacious chemoattractant for B cells than MIP-1α, a known B cell chemoattractant. CKβ-11/MIP-3β/ELC induced actin polymerization in lymphocytes, and chemotaxis was completely blocked by pertussis toxin showing its receptor, most likely EBI1/BLR2/CCR7, is coupled to a Gαi protein. CKβ-11/MIP-3β/ELC induced calcium mobilization in lymphocytes, which could be desensitized by SDF-1, suggesting possible cross-regulation in their signaling. Human CKβ-11/MIP-3β/ELC attracted murine splenocytes suggesting functional conservation of CKβ-11/MIP-3β/ELC between human and mouse. The efficacy of chemoattraction by CKβ-11/MIP-3β/ELC and tissue expression of its mRNA suggest that CKβ-11/MIP-3β/ELC may be important in trafficking of T cells in thymus, and T cell and B cell migration to secondary lymphoid organs.

Modulation of macrophage inflammatory protein-1alpha and its receptors in human B-cell lines derived from patients with acquired immunodeficiency syndrome and Burkitt's lymphoma

Macrophage inflammatory protein-1 alpha (MIP-1alpha) is a member of the -C-C- family of low-molecular weight chemokines. MIP-1alpha is involved in the homeostatic control of stem cell proliferation, in inducing chemotaxis, and also in inflammatory responses in mature cell types. In order to observe modulations of MIP-1alpha secretion and expression along with MIP-1alpha receptor (MIP-1alpha-R) expression for a possible autocrine role in AIDS associated B-cell lines, we studied a wide panel of human B-cell lines. Previous work by us has shown that HIV-1 tat down modulates MIP-1alpha by inducing a novel transcription factor MNP. Our data in this report suggest that HIV down modulates MIP-1alpha as a mechanism to evade suppression by this chemokine in human B-cells. Furthermore, our results strongly suggest MIP-1alpha autocrine loops in a majority of tumor B-cells as evident by MIP-1alpha-R expression, and also secretion of MIP-1alpha.

Recombinant LD78 protein, a member of the small cytokine family, enhances osteoclast differentiation in rat bone marrow culture system

Cytokine LD78 is a member of the small inducible protein family involved in cell growth, wound healing and inflammation. However, its exact function is not known. In this study, we demonstrated that recombinant LD78 alpha and its variant LD78 beta proteins stimulate osteoclast-like cell formation in rat bone marrow cultures in the presence of 1 alpha, 25-dihydroxyvitamin D3. This enhancing activity was independent of prostaglandin synthesis. This is the first report which describes the effect of proteins involved in the small inducible protein family on the differentiation of osteoclasts.

Suppressive effect of LD78 on the proliferation of human hemopoietic progenitors

LD78 is a cDNA newly isolated from human stimulated tonsillar lymphocytes. The expression of LD78 is related to inflammatory responses and its structure has a homology with macrophage inflammatory protein 1-alpha, which is known to have an inhibitory effect on murine CFU-S. Using a colony assay technique, we examined the effects of LD78 on human hemopoietic progenitors. The addition of doses of 100 ng/ml or more of LD78 suppressed the colony formation of KMT-2, a factor-dependent myelomonocytic cell line established from cord blood cells; this suppressive activity was neutralized by the addition of antibody against LD78. The same doses of LD78 suppressed the formation of neutrophil, macrophage, and megakaryocytic colonies which were supported by human interleukin-3 and erythropoietin; however, LD78 did not affect colony formation by either non-phagocytic mononuclear cells or sorted CD34+ cells. The conditioned medium of KMT-2 cells or peripheral blood mononuclear cells cultured with LD78 suppressed colony formation by CD34+ cells. From these findings, it is suggested that LD78 affects phagocytic cells and induces factors that are inhibitory for hemopoiesis. We consider LD78 to be a new cytokine that plays an inhibitory role in hemopoiesis.

Nucleotide sequence of the third cytokine LD78 gene and mapping of all three LD78 gene loci to human chromosome 17

Cytokine LD78 is a member of a newly identified cytokine superfamily. We cloned the third human gene for the LD78, termed LD78 gamma and the sequence analysis showed that it is a 5'-truncated pseudogene. Exons 2 and 3 and the intron between them are highly homologous to those of the LD78 beta gene, hence, the gamma gene was probably derived from the beta gene. Southern blot analysis of human x mouse somatic hybrid cell DNAs and in situ hybridization experiments mapped all the three gene loci on human chromosome 17q21.1-q21.3. Analysis of DNAs from family members supports our previous finding that the beta and gamma genes on each of the paired chromosome 17 vary in copy number and that the LD78 alpha gene is presumably a single copy. In our analyses of cosmid clones, the LD78 beta gene and the second gene for AT744, which is also a member of the superfamily are closely linked in a head-to-head arrangement. The mechanism of generation of the three LD78 genes is discussed.

Structures of human genes coding for cytokine LD78 and their expression

LD78 is a member of a newly identified superfamily of small inducible proteins involved in inflammatory responses, wound healing, and tumorigenesis. Southern blot analysis of the EcoRI-digested human genomic DNAs, using previously isolated LD78 cDNA as a probe, showed that in each individual there are 4.2- and 4.8-kilobase-pair (kb) fragments and that some have an additional 6.5-kb fragment. The 4.2-kb fragment contained genomic DNA sequences corresponding to the LD78 cDNA and was named the LD78 alpha gene. The 4.8-kb fragment contained similar sequences, showing 94% homology to the LD78 alpha gene, and was named the LD78 beta gene. The LD78 alpha gene was present in a single or a few copies per haploid genome, whereas the copy number of the LD78 beta gene and of the 6.5-kb fragment hybridizable to LD78 cDNA varied among the samples tested. Treatment of human myeloid cell lines HL-60 and U937 with phorbol 12-myristate 13-acetate (PMA) increased within 2 h cellular levels of the RNA hybridizable to LD78 cDNA. The human glioma cell line U105MG and primary culture of human fibroblasts also expressed the hybridizable RNA in response to PMA. Addition of cycloheximide had no apparent effect on this response in U937 cells and inhibited the response in fibroblasts, whereas it stimulated the response in HL-60 and U105MG cells. mRNA phenotyping experiments revealed that the LD78 alpha and LD78 beta genes were both transcribed in PMA-stimulated U937 cells.

Structures of human genes coding for cytokine LD78 and their expression

LD78 is a member of a newly identified superfamily of small inducible proteins involved in inflammatory responses, wound healing, and tumorigenesis. Southern blot analysis of the EcoRI-digested human genomic DNAs, using previously isolated LD78 cDNA as a probe, showed that in each individual there are 4.2- and 4.8-kilobase-pair (kb) fragments and that some have an additional 6.5-kb fragment. The 4.2-kb fragment contained genomic DNA sequences corresponding to the LD78 cDNA and was named the LD78 alpha gene. The 4.8-kb fragment contained similar sequences, showing 94% homology to the LD78 alpha gene, and was named the LD78 beta gene. The LD78 alpha gene was present in a single or a few copies per haploid genome, whereas the copy number of the LD78 beta gene and of the 6.5-kb fragment hybridizable to LD78 cDNA varied among the samples tested. Treatment of human myeloid cell lines HL-60 and U937 with phorbol 12-myristate 13-acetate (PMA) increased within 2 h cellular levels of the RNA hybridizable to LD78 cDNA. The human glioma cell line U105MG and primary culture of human fibroblasts also expressed the hybridizable RNA in response to PMA. Addition of cycloheximide had no apparent effect on this response in U937 cells and inhibited the response in fibroblasts, whereas it stimulated the response in HL-60 and U105MG cells. mRNA phenotyping experiments revealed that the LD78 alpha and LD78 beta genes were both transcribed in PMA-stimulated U937 cells.

Monocyte-derived neutrophil chemotactic factor (MDNCF/IL-8) resides in a gene cluster along with several other members of the platelet factor 4 gene superfamily

Monocyte-derived neutrophil chemotactic factor (MDNCF/IL-8, suggested gene symbol IL8) is a cytokine that chemoattracts and activates neutrophils. Using a panel of human-rodent cell hybrids that preferentially segregate human chromosomes and in situ hybridization, the MDNCF/IL-8 gene was placed on the human gene map at position 4q12-q21. This is the same location where at least three other members (platelet factor 4, melanoma growth stimulatory activity, and interferon-gamma induced factor) of the platelet factor 4 gene super-family reside. In addition, a restriction fragment length polymorphism was identified using MDNCF as a probe in screening genomic DNA digested with HindIII from unrelated individuals.

Synthesis of a novel cytokine and its gene (LD78) expressions in hematopoietic fresh tumor cells and cell lines

The gene coding for the protein LD78 was isolated from stimulated human tonsillar lymphocytes by differential hybridization. The gene product consisted of 92 amino acids with characteristics of cytokines. LD78 gene transcripts were detected in eight of eight fresh samples of cells from patients with acute nonlymphocytic leukemia (ANLL) by Northern blot analysis. ANLL cells with monocytic features gave the strongest bands. RNA transcripts were found in two of three samples of cells from patients with adult T cell leukemia (ATL), eight of nine samples from patients with acute lymphocytic leukemia (ALL) of B cell lineage, and one of the three samples from patients with T cell ALL. KG-1, HL-60, HUT 102, MT-2, and MJ cell lines expressed the LD78 gene constitutively. The LD78 protein was detected in culture supernatants and cell lysates of HUT 102, MT-2, MJ, and fresh ATL cells by Western blot analysis. This protein was not found in culture supernatants or cell lysates of monocytic leukemia cells and HL-60 cells, although LD78 transcripts were found in those cells. The discrepancy between gene and protein expression might be explained by the stability of the mRNA. Thus, the protein may be involved in the neoplastic transformation of hematopoietic cells.