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R A Koski

Publications and source records attributed to R A Koski.

At least 19 recordsLinked to original sources
PubMed2002

A novel family of anticoagulants from the saliva of Ixodes scapularis.

Using biochemical and molecular approaches, we have identified a 9.8 kDa protein in the saliva of Ixodes scapularis that inhibits the intrinsic pathway of coagulation. The 9.8 kDa anticoagulant protein was purified by reverse-phase HPLC and its N-terminal amino acid sequence determined. The N-terminal sequence showed homology with Salp14, an immuno-dominant antigen present in the saliva of engorging I. scapularis nymphs. Recombinant Salp14 expressed in Escherichia coli prolonged the activated partial thromboplastin time (APTT) of human plasma in a dose-dependent manner and was a specific inhibitor of factor Xa. A cDNA encoding a 9.3 kDa protein, Salp9Pac, was subsequently isolated from an I. scapularis salivary gland cDNA library. Salp9Pac showed 93% identity to the N-terminal sequence of the anticoagulant purified by HPLC. These data indicate that the anticoagulant protein purified by HPLC, Salp9Pac and Salp14 are members of a family of novel coagulation protease inhibitors present in tick saliva. While recombinant Salp9Pac did not show biological activity in the assays tested currently, it is likely to be mechanistically different from its paralogues. This raises the possibility that ticks may enhance their adaptive ability to cope with a wide spectrum of proteases, by transcribing such structurally related anticoagulant proteins with different functions.

Amino Acid Sequence↗
PubMed2001

Immunization of mice against West Nile virus with recombinant envelope protein.

West Nile (WN) virus is a mosquito-borne flavivirus that emerged in the United States in 1999 and can cause fatal encephalitis. Envelope (E) protein cDNA from a WN virus isolate recovered from Culex pipiens in Connecticut was expressed in Escherichia coli. The recombinant E protein was purified and used as Ag in immunoblot assays and immunization experiments. Patients with WN virus infection had Abs that recognized the recombinant E protein. C3H/HeN mice immunized with E protein developed E protein Abs and were protected from infection with WN virus. Passive administration of E protein antisera was also sufficient to afford immunity. E protein is a candidate vaccine to prevent WN virus infection.

Animals↗
PubMed2001

West Nile virus envelope protein: role in diagnosis and immunity.

The role of antibodies to the West Nile virus envelope (E) protein in serodiagnosis and protection was examined. The E protein was expressed and purified in recombinant form. Antibodies to the E protein were detected in patients with West Nile virus infection. Passive immunization with rabbit anti-E protein sera also partially protected mice from challenge with West Nile virus. The humoral response to the West Nile virus E protein is therefore useful as an aid in the diagnosis and may also play a role in immunity to infection.

Animals↗
PubMed2000

Hookworm burden reductions in BALB/c mice vaccinated with recombinant Ancylostoma secreted proteins (ASPs) from Ancylostoma duodenale, Ancylostoma caninum and Necator americanus.

Vaccination of mice with alum-precipitated recombinant Ancylostoma secreted protein-1 from the canine hookworm Ancylostoma caninum (Ac-ASP-1) results in protection against A. caninum larval challenge. Vaccine protection is manifested by host reductions in hookworm burden compared to control mice. The goal of this study was to determine whether ASP antigens cloned and expressed from different hookworm species will cross protect against A. caninum larval challenge. Cross-species protection against A. caninum challenge infections was observed with immunizations using recombinant ASP-1 from the human hookworms Ancylostoma duodenale and Necator americanus. However, the degree of protection was proportional to the extent of amino acid sequence homology between the ASP immunogen used for vaccination and the Ac-ASP-1 produced by the challenge larval strain. Vaccine protection was noted to decrease significantly as amino acid sequence homologies diverged 10% or more. It was also determined that Ac-ASP-2, a molecule cloned from A. caninum having 55% amino acid sequence homology to the C-terminus of Ac-ASP-1, did not elicit vaccine protection. These observations were partly reflected in the titer of antibodies that recognize Ac-ASP-1. The studies reported here will help to design immunogenic peptide vaccines based on the sequence divergence of hookworm ASPs.

Ancylostoma↗
PubMed1999

Experimental approaches to the development of a recombinant hookworm vaccine.

Hookworm infection is a major parasitic cause of morbidity in the developing nations of the tropics. Development of a genetically engineered vaccine would be a useful tool in the control of this infection in highly endemic areas. Recombinant polypeptides belonging to the Ancylostoma secreted protein (ASP)-1 family have shown promise for reducing hookworm burdens after larval challenge infections in mice. Typically, these polypeptides are expressed in Escherichia coli and administered as an alum precipitate. Vaccine protection is antibody dependent. It is anticipated that a cocktail of different recombinant hookworm antigens may be required in order to effectively prevent heavy hookworm infections and disease. The progress of this work has been hampered by the absence of both a convenient laboratory animal with which to study hookworm infections resembling human infection, as well as the lack of easy availability of native hookworm antigens. In addition, useful human serologic correlates of antihookworm immunity are still poorly defined.

Ancylostoma↗
PubMed1994

Cloning of cDNAs encoding human TIMP-3, a novel member of the tissue inhibitor of metalloproteinase family.

Proteins of the tissue inhibitor of metalloproteinase (TIMP) family bind and inactivate matrix metalloproteinases such as collagenases and gelatinases. We report the cloning and sequencing of cDNAs encoding a novel human TIMP, which we designated TIMP-3, the third member of the human TIMP family. Degenerate PCR primers derived from highly conserved regions of TIMP family cDNAs amplified a 402-bp product from human fetal kidney cDNA. This product and a related 333-bp PCR product were used as probes to screen two cDNA libraries. Three TIMP-3 cDNA clones were isolated, including a 1240-bp fetal kidney clone that contained a complete TIMP-3 precursor coding region of 211 amino acids (aa). The deduced precursor protein includes twelve Cys and 27 other aa that are invariant in the TIMP family. The predicted aa sequence is 89, 39 and 46% identical to those of ChIMP-3, human TIMP-1 and human TIMP-2, respectively. Northern blot analyses detected three TIMP-3 mRNA bands of 2.2, 2.5 and 4.4 kb in several human cell lines.

Amino Acid Sequence↗
PubMed1994

Synthesis, degradation, and subcellular localization of proteins encoded by the primary response genes TIS7/PC4 and TIS21/PC3.

Murine TIS7 and TIS21 cDNAs were cloned from phorbol ester-induced Swiss 3T3 cells. The cognate rat cDNAs, PC4 and PC3, were cloned from nerve growth factor (NGF)-treated PC12 pheochromocytoma cells. The TIS7/PC4 and TIS21/PC3 primary response genes are rapidly and transiently induced in response to serum, phorbol esters, and polypeptide growth factors in quiescent Swiss 3T3 cells and by NGF and other ligands in PC12 cells. In both 3T3 and PC12 cells the appearance of the TIS21/PC3 message precedes that of TIS7/PC4 message following ligand stimulation, suggesting that the TIS21/PC3 protein is likely to be synthesized more rapidly than the TIS7/PC4 protein. Using antisera prepared against recombinant TIS21 and TIS7 proteins, we find that the TIS21/PC3 protein is, indeed, synthesized more rapidly than the TIS7/PC4 protein following stimulation in both 3T3 and PC12 cells. In addition, "pulse-chase" experiments demonstrate that the TIS21/PC3 protein is degraded much more rapidly than the TIS7/PC4 protein. The sequences of the predicted PC3 and PC4 proteins have lead to the speculation that these two proteins may both be secreted from cells following stimulation. The PC4 protein is reported to have some sequence similarity to interferons. The TIS21/PC3 protein contains a presumptive leader sequence. Using our antisera to the recombinant proteins, however, we cannot detect secretion of radiolabelled TIS7/PC4 or TIS21/PC3 protein. Immunohistochemical and subcellular fractionation experiments suggest that the TIS7 protein is a membrane associated, non-nuclear intracellular protein. The TIS21 protein, in contrast, is a non-nuclear, soluble intracellular protein.

3T3 Cells↗
PubMed1994

Activation of the Axl receptor tyrosine kinase induces mitogenesis and transformation in 32D cells.

axl is a transforming receptor tyrosine kinase isolated from DNA of patients with chronic myelogenous leukemia. Association of axl expression with myelogenous leukemias and its expression in primitive hematopoietic cells suggests a role for axl in myeloid biology. To study the cellular function of axl, we constructed a chimeric receptor tyrosine kinase composed of the extracellular and transmembrane domains of the EGF receptor and the cytoplasmic domain of axl; this chimera was named EAK for EGFR-Axl-Kinase. The EAK chimeric receptor was expressed in the mouse myeloid progenitor cell line 32D, which is dependent on interleukin 3 (IL-3) for proliferation and survival. Treatment of the 32D-EAK cells with EGF stimulated the tyrosine phosphorylation of the axl kinase domain and enabled proliferation through EGF rather than IL-3. Thus, axl can effectively couple with mitogenic signaling pathways intrinsic to 32D myeloid cells. Assay of proteins phosphorylated in response to different cytokine treatments showed that IL-3 and EGF exposure produced unique profiles in the 32D-EAK cells. Furthermore, Jak-2 is phosphorylated only in response to IL-3 treatment in these cells. This suggests that IL-3 receptor and axl transduce mitogenic signals through separate pathways. In addition, exposure of cells expressing the chimeric receptor to EGF for 19 days converted the cells to factor-independent growth, a phenomenon not seen with other receptor tyrosine kinases. Generation of this transformed phenotype is absolutely dependent on axl activation by foster ligand. The tyrosine phosphorylation level of the axl kinase domain in the factor-independent subclones is 40-fold greater than the factor-dependent cells. The association of a unique axl phosphorylation level with the factor-independent phenotype suggests that there is a threshold phosphorylation level of the axl kinase for transformation. The fact that activation of the axl receptor leads to transformation of 32D cells suggests that axl can play a role in leukemic conversion of myeloid cells, either through inappropriate expression or improper activation.

Animals↗
PubMed1993

Cytokines in inflammatory malignant fibrous histiocytoma presenting with leukemoid reaction.

Inflammatory malignant fibrous histiocytomas (IMFH) are rare tumors and are frequently associated with leukocytosis. In rare cases, leukemoid reactions were attributed to tumor production of unidentified hematopoietic factors. In this study, we used immunohistochemical techniques to show cytokine immunoreactivity in the malignant cells of two cases of IMFH presenting with leukemoid reactions and compared them with two malignant fibrous histocytomas, noninflammatory type. All four tumors stained positively for stem cell factor (SCF), granulocyte colony-stimulating factor (G-CSF), interleukin-2 (IL-2), IL-4, IL-5, interferon-alpha (IFN-alpha), and insulin-like growth factor-I. Other cytokines detected only in the two IMFH included IL-6, IL-7, IL-8, IFN-gamma, and keratinocyte growth factor. Granulocyte-macrophage-CSF, IL-3, and transforming growth factor-beta staining was present in one of the two IMFH tumors and was not present in the noninflammatory tumors. The immunohistochemical staining was localized to the malignant cells, suggesting deregulated cytokine expression consistent with their monocytic/histocytic origin. Expression of certain cytokines in the IMFH may account for the local inflammatory infiltrate, tumor fibrosis, and the aggressive nature of the malignant cells. We also detected elevated serum levels of SCF, G-CSF, IL-6, and tumor necrosis factor in one or both of the IMFH patients. These latter observations may explain the bone marrow hypercellularity and other paraneoplastic symptoms, including fever, malaise, and weight loss, observed in both patients. Different cytokines present in the two IMFH tumors appear to be responsible for the eosinophilic leukemoid reaction observed in one case and for the granulocytic leukemoid reaction observed in the other patient. They may also be responsible for expansion of the tumor-cell population, fibroblast proliferation, and enhanced secretion of extracellular collagen.

Aged↗
PubMed1993

Expression of the gastrin gene in the normal human colon and colorectal adenocarcinoma.

Gastrin, produced in the G-cells of the gastric antrum and regulating acid secretion in the stomach, also acts as a trophic factor in the gastrointestinal tract. Because of its possible role in colon cell proliferation and differentiation, evidence for its presence in normal colorectal mucosa and adenocarcinoma was sought. Utilizing tumors and matched normal mucosa from 26 patients, mature gastrin and progastrin were studied by immunohistochemistry. In normal colonic mucosal crypts, occasional cells stained concordantly for gastrin, progastrin, and chromogranin A, suggesting that they are of neuroendocrine origin. Adenomatous polyps stained neither for gastrin nor chromogranin A. In 22 of 23 adenocarcinomas, more than 50% of tumor cells stained for gastrin and progastrin. The expected gastrin transcript was demonstrable by polymerase chain reaction and RNase protection in tumors and by polymerase chain reaction in normal mucosa. Its identity was confirmed by sequencing the polymerase chain reaction product. A larger transcript containing Intron II was present in both cancers and normal mucosa but was barely discernible in the gastric antrum. Aberrant expression of gastrin may contribute to deregulated proliferation of many colorectal carcinomas.

Amino Acid Sequence↗
PubMed1992

Distribution of cells expressing myc proteins in human colorectal epithelium, polyps, and malignant tumors.

The myc gene family encodes nuclear phosphoproteins that are thought to play a role in the control of cellular proliferation and differentiation. We have undertaken an immunohistochemical study assessing the expression of myc gene family proteins in individual cells of normal colonic mucosa, colorectal polyps, and colorectal adenocarcinomas. We screened a panel of mouse monoclonal antibodies that we raised against recombinant human c-myc and N-myc proteins for recognition of myc proteins in paraffin tissue sections. Two of these antibodies, H120C69 and H8C150, were selected for indirect immunoperoxidase staining of tissue sections from 16 normal mucosas, 24 polyps, and 30 adenocarcinomas. In normal colon, about 25% of the cells in the lower one-third of the crypts of Lieberkühn stain for myc-related protein. This distribution resembles that of proliferating cells in the crypt. Benign hyperplastic polyps resemble normal mucosa in their myc staining pattern, with about 25% of the cells positive. In adenomatous polyps, the putative precursors of adenocarcinomas, from 50 to 100% of the cells stain positively for myc protein. In these cases, stained cells extend to the luminal surface, consistent with the previously reported expansion of the proliferation zone in these lesions. All adenocarcinomas examined had increased levels of myc protein relative to normal mucosa. The tumor cells exhibited markedly heterogeneous myc staining patterns, both among different tumors and, in some cases, within a single tumor. Comparison with Ki-67 monoclonal antibody staining indicates that myc protein expression in many tumors is uncoupled from cellular proliferation. Surprisingly, we observed increased numbers of myc-expressing cells and increased levels of myc protein in histologically normal colon directly adjacent to tumor, suggesting that many colorectal carcinomas secrete growth factors that activate gene expression in neighboring normal mucosa.

Adenocarcinoma↗
PubMed1992

Isolation of the neu/HER-2 stimulatory ligand: a 44 kd glycoprotein that induces differentiation of mammary tumor cells.

The neu/HER-2 proto-oncogene (also called erbB-2) encodes a transmembrane glycoprotein related to the epidermal growth factor receptor. We have purified to homogeneity a 44 kd glycoprotein from the medium of ras-transformed cells that stimulates phosphorylation of the Neu protein and retains activity after elution from the polyacrylamide gel. The protein is active at picomolar concentrations and displays a novel N-terminal sequence. Cross-linking experiments with radiolabeled p44 result in specific labeling of Neu, indicating that p44 is a ligand for Neu or a related receptor. The purified protein induces phenotypic differentiation of cultured human breast cancer cells, including altered morphology and synthesis of milk components. This is accompanied by an increase in nuclear area, inhibition of cell growth (probably by cell cycle arrest at the late S or the G2/M phases), and induction of DNA polyploidy. We propose the name Neu differentiation factor (NDF) for p44.

Amino Acid Sequence↗
PubMed1991

Structure and expression of TIS21, a primary response gene induced by growth factors and tumor promoters.

The TIS21 gene is a primary response gene that is induced rapidly and transiently in 3T3 cells by the tumor promoter and mitogen tetradecanoyl phorbol acetate. The predicted open reading frame of the TIS21 cDNA encodes a protein of 158 amino acids with no obvious similarity to any known protein. Antiserum prepared to TIS21 recombinant protein produced in Escherichia coli precipitates a 17-kDa protein from Swiss 3T3 cells. The 2040-nucleotide 3'-untranslated region of the cDNA includes an unusual T18 sequence. The TIS21 gene has a single 1.4-kilobase intron which interrupts the open reading frame and is otherwise identical to the cDNA sequence. The 5'-flanking sequence of the TIS21 gene contains TATA and CAAT box-type sequences, three potential Sp1 sites, two putative cyclic AMP response elements, two potential AP1 binding elements, and an AP2 element. A possible Z-DNA structure of 29 AC repeats is present 660 nucleotides from the start of transcription. Expression from a luciferase reporter construct containing a 460-nucleotide fragment of the TIS21 promoter is induced by tetradecanoyl phorbol acetate, forskolin, epidermal growth factor, and serum, despite the absence of a consensus serum response element.

Amino Acid Sequence↗
PubMed1990

Identification and characterization of the Egr-1 gene product, a DNA-binding zinc finger protein induced by differentiation and growth signals.

Egr-1 is an immediate-early response gene induced by diverse signals that initiate growth and differentiation. Its cDNA sequence predicts a protein with zinc fingers. We have generated an antiserum to the Egr-1 gene product and identified it as an 80-kilodalton short-lived protein in serum-stimulated mouse fibroblasts. The rat Egr-1 product has also been identified in nerve growth factor-induced PC12 cells. In addition, we show by cell fractionation and immunocytochemistry that the Egr-1 protein is located in the nucleus. We also demonstrate that it is phosphorylated. In vitro-generated Egr-1 protein binds with high affinity to the sequence CGCCCCCGC in a zinc-dependent manner.

Animals↗
PubMed1986

Highly mutable sites for ICR-170-induced frameshift mutations are associated with potential DNA hairpin structures: studies with SUP4 and other Saccharomyces cerevisiae genes.

The majority of the mutations induced by ICR-170 in both the CYC1 gene (J. F. Ernst et al. Genetics 111:233-241, 1985) and the HIS4 gene (L. Mathison and M. R. Culbertson, Mol. Cell. Biol. 5:2247-2256, 1985) of the yeast Saccharomyces cerevisiae were recently shown to be single G . C base-pair insertions at monotonous runs of two or more G . C base pairs. However, not all sites were equally mutable; in both the CYC1 and HIS4 genes there is a single highly mutable site where a G . C base pair is preferentially inserted at a [sequence in text]. Here we report the ICR-170 mutagen specificity at the SUP4-o tyrosine tRNA gene of yeast. Genetic fine structure analysis and representative DNA sequence determination of ICR-170-induced mutations revealed that there is also a single highly mutable site in SUP4-o and that the mutation is a G . C base-pair insertion at a monotonous run of G . C base pairs. Analysis of DNA sequences encompassing the regions of highly mutable sites for all three genes indicated that the mutable sites are at the bases of potential hairpin structures; this type of structure could not be found at any of the other, less mutable G . C runs in SUP4, CYC1, and HIS4. Based on these results and recent information regarding novel DNA structural conformations, we present a mechanism for ICR-170-induced mutagenesis. (i) ICR-170 preferentially binds to DNA in the beta conformation; factors that increase the temporal stability of this structure, such as adjacent stem-and-loop formation, increase the frequency of ICR-170 binding; (ii) the observed mutagen specificity reflects formation of a preferred ICR-170 intercalative geometry at [sequence in text] sites; (iii) during replication or repair, ICR-170 remains associated with the single-stranded template; (iv) stuttering or strand slippage by the polymerization complex as it encounters the mutagen results in nucleotide duplication; (v) subsequent replication or mismatch repair fixes the insertion into the genome. This mechanism accounts for both the IRC-170 mutagenic specificity and the molecular basis of the highly mutable sites in S. cerevisiae.

Aminoacridines↗
PubMed1982

An in vitro RNA polymerase III system from S. cerevisiae: effects of deletions and point mutations upon SUP4 gene transcription.

A soluble cell-free extract containing RNA polymerase III and factors essential for selective transcription of the yeast SUP4-o tRNATyr gene was prepared from Saccharomyces cerevisiae cells. An intragenic promoter for yeast RNA polymerase III was identified within the yeast tRNATyr coding sequence by testing several sup4 genes with 5'- and 3'-terminal deletions in the homologous transcription system. Thirty-four different sup4 genes with spontaneous mutations were also tested in the in vitro system. Two point mutations drastically reduced transcription initiation and two other mutations caused premature termination. These mutations have nearly identical effects on SUP4 gene transcription by Xenopus RNA polymerase III (1), which demonstrates that the essential features of RNA polymerase III transcription initiation and termination signals have been conserved throughout the course of eukaryotic evolution.

Base Sequence↗
PubMed1982

Synthesis and maturation of Xenopus laevis methionine tRNA gene transcripts in homologous cell-free extracts.

A cloned initiator methionine tRNA gene from Xenopus laevis has been transcribed in cell-free extracts (S-100) prepared from cultured X. laevis kidney cells. RNA polymerase III produces two primary transcripts of this gene which initiate with a pppG and a pppA located seven and four nucleotides, respectively, in front of the mature tRNAMet1 5' end. Both terminate with a dT5 tract just beyond the nucleotides encoding the mature tRNA. The tRNA precursors are readily processed in vitro to mature length tRNA which contains six of the seven modified nucleotides found in the in vivo tRNAMet1. Many of these ribonucleotide modifications (m1G, m2G, m7G, D, and m1A) are introduced into the primary transcripts. The single exception is t6A which is found in the tRNAMet1 anticodon loop only after maturation of the 5' and 3' termini.

Animals↗