Primary structure of lymphocyte function-associated antigen 3 (LFA-3). The ligand of the T lymphocyte CD2 glycoprotein.

We have isolated the cDNA for human lymphocyte function-associated antigen 3 (LFA-3), the ligand of the T lymphocyte CD2 molecule. The identity of the clones was established by comparison of the deduced amino acid sequence to the LFA-3 NH2-terminal and tryptic peptide sequences. The cDNA defines a mature protein of 222 amino acids that structurally resembles typical membrane-anchored proteins. An extracellular domain with six N-linked glycosylation sites is followed by a hydrophobic putative transmembrane region and a short cytoplasmic domain. The mature glycoprotein is estimated to be 44-68% carbohydrate. Southern blots of human genomic DNA indicate that only one gene codes for human LFA-3. Northern blot analysis demonstrates that the LFA-3 mRNA of 1.3 kb is widely distributed in human tissues and cell lines.

Uromodulin (Tamm-Horsfall glycoprotein): a renal ligand for lymphokines.

The protein portion of the immunosuppressive glycoprotein uromodulin is identical to the Tamm-Horsfall urinary glycoprotein and is synthesized in the kidney. Evidence that the glycoproteins are the same is based on amino acid sequence identity, immunologic cross-reactivity, and tissue localization to the thick ascending limb of Henle's loop. Nucleic acid sequencing of clones for uromodulin isolated from a complementary DNA bank from human kidney predicts a protein 639 amino acids in length, including a 24--amino acid leader sequence and a cysteine-rich mature protein with eight potential glycosylation sites. Uromodulin and preparations of Tamm-Horsfall glycoprotein bind to recombinant murine interleukin-1 (rIL-1) and human rIL-1 alpha, rIL-1 beta, and recombinant tumor necrosis factor (rTNF). Uromodulin isolated from urine of pregnant women by lectin adherence is more immunosuppressive than material isolated by the original salt-precipitation protocol of Tamm and Horsfall. Immunohistologic studies demonstrate that rIL-1 and rTNF bind to the same area of the human kidney that binds to antiserum specific for uromodulin. Thus, uromodulin (Tamm-Horsfall glycoprotein) may function as a unique renal regulatory glycoprotein that specifically binds to and regulates the circulating activity of a number of potent cytokines, including IL-1 and TNF.

A lymphotoxin-beta-specific receptor.

Tumor necrosis factor (TNF) and lymphotoxin-alpha (LT-alpha) are members of a family of secreted and cell surface cytokines that participate in the regulation of immune and inflammatory responses. The cell surface form of LT-alpha is assembled during biosynthesis as a heteromeric complex with lymphotoxin-beta (LT-beta), a type II transmembrane protein that is another member of the TNF ligand family. Secreted LT-alpha is a homotrimer that binds to distinct TNF receptors of 60 and 80 kilodaltons; however, these receptors do not recognize the major cell surface LT-alpha-LT-beta complex. A receptor specific for human LT-beta was identified, which suggests that cell surface LT may have functions that are distinct from those of secreted LT-alpha.

BAFF-R, a newly identified TNF receptor that specifically interacts with BAFF.

B cell homeostasis has been shown to critically depend on BAFF, the B cell activation factor from the tumor necrosis factor (TNF) family. Although BAFF is already known to bind two receptors, BCMA and TACI, we have identified a third receptor for BAFF that we have termed BAFF-R. BAFF-R binding appears to be highly specific for BAFF, suggesting a unique role for this ligand-receptor interaction. Consistent with this, the BAFF-R locus is disrupted in A/WySnJ mice, which display a B cell phenotype qualitatively similar to that of the BAFF-deficient mice. Thus, BAFF-R appears to be the principal receptor for BAFF-mediated mature B cell survival.

Starvation phase of Physarum polycephalum: characterization of transfer ribonucleic acid.

We have begun a series of studies designed to characterize gene expression during differentiation in the slime mold Physarum polycephalum. This work concerns the starvation phase of the sporulation sequence and describes some of the quantitative changes which occur in plasmodial constituents during the 3-day starvation period and also describes alterations in the transfer ribonucleic acid (tRNA) population. The results show that whereas the plasmodial tRNA content decreased by 75% during starvation, concurrent de novo synthesis of tRNA also occurred, and they also show that overall amino acid acceptor activity of the starvation-phase tRNA population did not differ significantly from that found in the growth phase. Of the 19 starvation-phase tRNA families assayed, however, 6 were found to have consistently lower acceptor activities than did their growth-phase counterparts. Reverse-phase (RPC-5) chromatographic analysis of five of those families failed to reveal any major differences between growth- and starvation-phase isoacceptors. The data suggest that the depletion and resynthesis of tRNA during the starvation phase results in a quantitative alteration in the composition of the tRNA population and that the alteration is tRNA family and not tRNA isoacceptor specific.

Phenotypic expression in Escherichia coli and nucleotide sequence of two Chinese hamster lung cell cDNAs encoding different dihydrofolate reductases.

Nucleotide sequence analysis of two cDNA clones, one shown to direct the synthesis in Escherichia coli of the pI 6.7 form of the 20,000-molecular-weight class of Chinese hamster lung cell dihydrofolate reductase, and the other shown to direct the synthesis of the pI 6.5 form of the 21,000-molecular-weight class of the enzyme, has revealed the following: (i) the differences in physical and enzymatic properties displayed by these two proteins are due to two variations in their respective amino acid sequences with the conversion of Leu to Phe at position 22 probably responsible for the differential sensitivity of these two enzymes to methotrexate and methasquin; (ii) the multiple mRNAs responsible for the synthesis of each of these proteins differ in size due, at least in part, to a length heterogeneity at their 3' ends; (iii) these two proteins are encoded by different genes; and (iv) the sequence AAATATA appears to be a major polyadenylation signal in one Chinese hamster lung cell dihydrofolate reductase gene and a minor signal in another.

Plasminogen activator inhibitor 2: regulation of gene transcription during phorbol ester-mediated differentiation of U-937 human histiocytic lymphoma cells.

We have isolated and sequenced two cDNA clones coding for plasminogen activator inhibitor 2 (PAI-2). The cDNA was used to study the regulation of PAI-2 gene transcription by the tumor-promoting phorbol ester phorbol 12-myristate 13-acetate in the human histiocytic lymphoma cell line U-937. The tumor promoter caused a transient, 50-fold increase of PAI-2 gene transcription.

Genomic structure and chromosomal localization of the human GDNFR-alpha gene.

GDNFR-alpha is a glycosyl-phosphotidylinositol-linked receptor for glial cell line-derived neurotrophic factor (GDNF). GDNF binds to GDNFR-alpha and this complex, in turn, is believed to interact with the RET receptor tyrosine kinase to effect downstream signalling. GDNFR-alpha belongs to a novel gene family without strong homology to known genes. Thus, little information has been available to help predict genomic structure or location of this gene. In this study, the genomic organization of human GDNFR-alpha was delineated through a combination of PAC clone characterization, long distance PCR and sequence analyses. Exon-intron boundaries were defined by comparing the size and sequence of the genomic PCR products to those predicted by the cDNA sequence. The human GDNFR-alpha gene comprises 9 exons. GDNFR-alpha PAC clones were used for FISH analysis to map this gene to 10q26.

Identification of mRNA in the slime mold Physarum polycephalum.

Using a differential extraction procedure which had previously been shown to yield one nucleic acid fraction enriched in cytoplasmic RNA and another enriched in nuclear RNA, we have been able to isolate two polyadenylated RNA populations from microplasmodia of Physarum polycephalum. The poly(A)-containing RNA from the cytoplasmic-enriched fraction accounts for approximately 1.2% of the cytoplasmic nucleic acid, has a number-average nucleotide size of 1339+/- 39 nucleotides, and has been shown, in a protein-synthesizing system in vitro, to be capable of directing the synthesis of peptides which have also been shown to be synthesized in vivo by microplasmodia. The poly(A)-containing RNA from the nuclear-enriched fraction has a number-average nucleotide size of 1533 +/- 104 nucleotides and represents a mixture of cytoplasmic and nuclear adenylated RNA molecules. Based upon these observations, we have identified the polyadenylated RNA isolated from the fraction enriched in cytoplasmic nuclei acid as Physarum poly(A)-containing messenger RNA.

Combinations of tetrahydrouridine and cytosine arabinoside in mouse tumors.

Thirteen experimental mouse neoplasms were tested by cytidine (CR)-deaminase and deoxycytidine (dCR)-kinase levels. Four neoplasms, Sarcoma T241, Adenocarcinoma E0771, Lewis lung carcinoma (LL), and Sarcoma 180 Japan (S180J), considered to have high deaminase and sufficient dCR-kinase activities, were tested in vivo for combination chemotherapy with cytosine arabinoside (ara-C) and the CR-deaminase inhibitor, tetrahydrouridine (THU). THU did not significantly improve the growth inhibition of ara-C in a wide range of combinations in T241, E0771, LL, and the solid form of S180J, but more than doubled the survival time of the S180J ascites-bearing animals. Toxicity in the form of weight loss and toxic deaths was observed in some but not all groups, especially at high dosages of ara-C and THU. Tissue distribution of [3H]-ara-C and [14C]-THU in T241-bearing mice revealed an accelerated clearance of ara-C-derived radioactivity under the influence of THU in the tumor and five host tissues, but not in the small intestines. With the exception of the small intestines, clearance of THU-derived radioactivity was faster in all tissues studied compared to the clearance of [3H]-ara-C-derived radioactivity. Intracellular CR-deaminase levels were inhibited significantly, ie, dose dependent, in tumor and host kidney after a single ip injection of THU to E0771--bearing mice. In the solid S180J, with or without simultaneous ip administration of THU, [3H]-ara-C was not converted to 5'-di- and tri-phosphates at all. In mice bearing the ascites form of S180J, [3H]-ara-C was extensively converted to ara-C 5'-di- and tri-phosphates. THU increased both overall ara-C-derived radioactivity and the relative amounts of ara-C 5'-di- and tri-phosphates.

Expression, purification and biochemical comparison of natural and recombinant human non-pancreatic phospholipase A2.

The gene coding for human non-pancreatic phospholipase A2 (npPLA2) was cloned in a eukaryotic expression vector and transfected into chinese hamster ovary (CHO) cells. A number of cell lines stably expressing npPLA2 were obtained. Northern analysis of these cell lines showed an abundant transcript of expected size 1200 nt. The recombinant enzyme was efficiently secreted in quantities up to 400 micrograms npPLA2 per liter culture medium in the most productive cell lines. npPLA2 was purified to homogeneity from conditioned medium as previously described (1). The recombinant npPLA2 migrated by SDS--PAGE as a single band with an apparent mass of 14,000. The recombinant enzyme displayed the pH-optimum, calcium dependence and substrate preference that were characteristic of the human platelet and synovial fluid enzymes.

Cloning of an inflammation-specific phosphatidyl inositol-linked form of murine vascular cell adhesion molecule-1.

Vascular cell adhesion molecule-1 (VCAM1) is a member of the immunoglobulin (Ig) superfamily which interacts with the integrin very late antigen-4 (VLA4). The VCAM1/VLA4 interaction mediates both adhesion and signal transduction and is thought to play an important role in inflammatory and immune responses in vivo. VCAM1 cDNAs cloned from mouse, rat, rabbit, and human libraries contain six, seven, or eight extracellular Ig-like domains generated by alternate splicing, but to date shorter forms have not been found. We have cloned a novel cDNA encoding only the three N-terminal domains of murine VCAM1 followed by a unique C-terminal tail generated by alternate splicing of a previously undescribed exon. This truncated form of murine VCAM1 (3D-VCAM1) is expressed in COS cells as a functional adhesion molecule which is lost from the cell surface following treatment with phosphatidylinositol-specific phospholipase C. 3D-VCAM1 is found only in endotoxin-treated but not control murine and rat tissues. Thus in rodents alternate splicing of the VCAM1 gene generates a unique truncated inflammation-specific phosphatidylinositol-linked form of VCAM1.

Antifolate-resistant Chinese hamster cells. Evidence for dihydrofolate reductase gene amplification among independently derived sublines overproducing different dihydrofolate reductases.

Purification of a cDNA probe specific for dihydrofolate reductase mRNA has allowed the relative quantification of dihydrofolate reductase gene numbers and mRNA levels between a line of Chinese hamster lung fibroblasts sensitive to the antifolate drugs methotrexate and methasquin and sublines which by virtue of their overproduction of the target enzyme dihydrofolate reductase are cross-resistant to these site-specific inhibitors. Previous results have shown that resistant sublines could overproduce one of two molecular weight forms of dihydrofolate reductase, one parental-like (Mr = 21,000) and one nonparental-like (Mr = 20,000), each encoded by a different mRNA present in elevated amounts in resistant cells (Melera, P. W., Wolgemuth, D., Biedler, J. L., and Hession, C. (1980). J. Biol. Chem. 255, 319--322). The cDNA-RNA and cDNA-DNA hybridization experiments reported here confirm the elevated levels of dihydrofolate reductase-specific mRNA in resistant cells and show that the overproduction of either molecular weight form of dihydrofolate reductase is accompanied by amplification in dihydrofolate reductase gene number.

Aminoacyl-tRNAs from Physarum polycephalum: patterns of codon recognition.

Isoacceptors of Physarum polycephalum Ala-, Arg-, Glu-, Gln-, Gly-, Ile-, Leu-, Lys-, Ser-, Thr-, and Val-tRNAs were resolved by reverse-phase chromatography and isolated, and their codon recognition properties were determined in a ribosomal binding assay. Codon assignments were made to most isoacceptors, and they are summarized along with those determined in other studies from Escherichia coli, yeasts, wheat germ, hymenoptera, Xenopus, and mammals. The patterns of codon recognition by isoacceptors from P. polycephalum are more similar to those of animals than to those of plants or lower fungi.

Antifolate-resistant chinese hamster cells. Evidence from independently derived sublines for the overproduction of two dihydrofolate reductases encoded by different mRNAs.

A comparison by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the proteins synthesized by antifolate-sensitive (DC-3F) and -resistant (DC-3F/A3 and DC-3F/MQ19) Chinese hamster lung fibroblast cells has shown that an apparent molecular weight difference exists between the dihydrofolate reductases overproduced by the resistant sublines. Translation in a rabbit reticulocyte lysate system of polysomal and cytoplasmic mRNAs from the three sublines has shown that the overproduction of dihydrofolate reductase by resistant cells is accompanied by increased levels of dihydrofolate reductase-specific mRNA and that the different molecular weight forms of dihydrofolate reductase are encoded by their respective mRNAs.

Preparation and characterization of soluble recombinant heterotrimeric complexes of human lymphotoxins alpha and beta.

The lymphotoxin (LT) protein complex is a heteromer of alpha (LT-alpha, also called tumor necrosis factor (TNF)-beta) and beta (LT-beta) chains anchored to the membrane surface by the transmembrane domain of the LT-beta portion. Both proteins belong to the TNF family of ligands and receptors that regulate aspects of the immune and inflammatory systems. The LT complex is found on activated lymphocytes and binds to the lymphotoxin-beta receptor, which is generally present on nonlymphoid cells. The signaling function of this receptor-ligand pair is not precisely known but is believed to be involved in the development of the peripheral lymphoid organs. To analyze the properties of this complex, a soluble, biologically active form of the surface complex was desired. The LT-beta molecule was engineered into a secreted form and co-expressed with LT-alpha using baculovirus/insect cell technology. By exploiting receptor affinity columns, the LT-alpha3, LT-alpha2/beta1, and LT-alpha1/beta2 forms were purified. All three molecules were trimers, and their biochemical properties are described. The level of LT-alpha3-like components in the LT-alpha1/beta2 preparation was found to be 0.02% by following the activity of the preparation in a WEHI 164 cytotoxicity assay. LT-alpha3 with an asparagine 50 mutation (D50N) cannot bind the TNF receptors. Heteromeric LT complexes were prepared with this mutant LT- alpha form, allowing a precise delineation of the extent of biological activity mediated by the TNF receptors. A LT-alpha3 based cytotoxic activity was used to show that the LT-alpha1/beta2 form cannot readily scramble into a mixture of forms following various treatments and storage periods. This biochemical characterization of the LT heteromeric ligands and the demonstration of their stability provides a solid foundation for both biological studies and an analysis of the specificity of the LT-bet a and TNF receptors for the various LT forms.

Kidney injury molecule-1 (KIM-1), a putative epithelial cell adhesion molecule containing a novel immunoglobulin domain, is up-regulated in renal cells after injury.

We report the identification of rat and human cDNAs for a type 1 membrane protein that contains a novel six-cysteine immunoglobulin-like domain and a mucin domain; it is named kidney injury molecule-1 (KIM-1). Structurally, KIM-1 is a member of the immunoglobulin gene superfamily most reminiscent of mucosal addressin cell adhesion molecule 1 (MAdCAM-1). Human KIM-1 exhibits homology to a monkey gene, hepatitis A virus cell receptor 1 (HAVcr-1), which was identified recently as a receptor for the hepatitis A virus. KIM-1 mRNA and protein are expressed at a low level in normal kidney but are increased dramatically in postischemic kidney. In situ hybridization and immunohistochemistry revealed that KIM-1 is expressed in proliferating bromodeoxyuridine-positive and dedifferentiated vimentin-positive epithelial cells in regenerating proximal tubules. Structure and expression data suggest that KIM-1 is an epithelial cell adhesion molecule up-regulated in the cells, which are dedifferentiated and undergoing replication. KIM-1 may play an important role in the restoration of the morphological integrity and function to postischemic kidney.