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E J Filardo

Publications and source records attributed to E J Filardo.

11 recordsLinked to original sources
PubMed1996

Molecular cloning of a human melanoma-associated chondroitin sulfate proteoglycan.

A human melanoma-associated chondroitin sulfate proteoglycan (MCSP), recognized by mAb 9.2.27, plays a role in stabilizing cell-substratum interactions during early events of melanoma cell spreading on endothelial basement membranes. We report here the molecular cloning and nucleotide sequencing of cDNA encoding the entire core protein of human MCSP and provide its deduced amino acid sequence. This core protein contains an open reading frame of 2322 aa, encompassing a large extracellular domain, a hydrophobic transmembrane region, and a relatively short cytoplasmic tail. Northern blot analysis indicated that MCSP cDNA probes detect a single 8.0-kb RNA species expressed in human melanoma cell lines. In situ hybridization experiments with a segment of the MCSP coding sequence localized MCSP mRNA in biopsies prepared from melanoma skin metastases. Multiple human Northern blots with an MCSP-specific probe revealed a strong hybridization signal only with melanoma cells and not with other human cancer cells or a variety of human fetal and adult tissues. These data indicate that MCSP represents an integral membrane chondroitin sulfate proteoglycan expressed by human malignant melanoma cells. The availability of cDNAs encoding MCSP should facilitate studies designed to establish correlations between structure and function of this molecule and help to establish its role in the progression of human malignant melanoma.

Adult↗
PubMed1996

Osteopontin activation of c-src in human melanoma cells requires the cytoplasmic domain of the integrin alpha v-subunit.

In human melanoma cells, expression of the alpha v beta 3 integrin is correlated with the metastatic potential. The expression of osteopontin (OPN or OP), a protein ligand for the integrin alpha v beta 3, also correlates with metastatic potential of some tumors. Analysis of signal transduction, stimulated by OPN/alpha v beta 3 in human melanoma cells (M21), revealed activation of pp60c-src associated with the integrin. pp60c-src stimulation by OPN was dose dependent, and it was inhibited in vitro by a tyrosine kinase inhibitor, herbimycin-A. To determine the need for the cytoplasmic domain of the alpha v-subunit, in the association of pp60c-src with alpha v beta 3, a cell line expressing truncated alpha v was studied. M21-L cells lacked alpha v expression but stably transfected with complementary DNAs encoding alpha v full length protein alpha v 1018 or alpha v 995 (lacking 23 carboxyl-terminal amino acids), and a fibroblast cell line (FG) expressing alpha v beta 5 but not alpha v beta 3, were used. Western analysis and immune complex kinase assays of anti- alpha v immunoprecipitates demonstrated that M21-L/alpha v995 cells did not exhibit pp60c-src association with alpha v, whereas the alpha v1018 complementary DNA transfected cells and FG cells had pp60c-src associated with the alpha v integrins. Immunofluorescence analysis revealed pp60c-src, alpha v beta 3 integrin, and actin distribution along the plasma membrane of M21 cells. 35S-labeling of cells and analysis of complexes immunoprecipitated by a monoclonal antibody against alpha v beta 3 demonstrated association of actin with the immune complexes. We conclude that OPN stimulates pp60c-src kinase activity associated with the alpha v beta 3 integrin and that the association requires the cytoplasmic tail of the alpha v chain.

Actins↗
PubMed1996

Regulation of cell migration by the integrin beta subunit ectodomain.

CS-1 melanoma cells transfected with cDNAs encoding either the beta 3 or beta 5 integrin subunit protein express alpha v beta 3 or alpha v beta 5, respectively, enabling them to adhere to vitronectin yet only alpha v beta 3 promotes cell spreading and migration on this substrate. Following exposure to insulin or insulin-like growth factor, alpha v beta 5-expressing CS-1 cells gain the ability to migrate on vitronectin. To identify structural regions in beta 3 or beta 5 that account for these distinct biological properties, CS-1 cells were transfected with one of two chimeric beta subunit proteins, in which the ecto- and cytoplasmic domains of beta 3 and beta 5 were exchanged (termed alpha v beta 3/5 or alpha v beta 5/3). Surprisingly, alpha v beta 3/5 expressing cells spread and migrate on vitronectin while cells expressing alpha v beta 5/3 do not unless they are exposed to cytokine. These findings suggest that the distinct migratory properties mediated by integrins alpha v beta 3 and alpha v beta 5 and their response to cytokine activation is determined by a sequence(s) within the ectodomain of the integrin beta subunit.

Animals↗
PubMed1995

Requirement of the NPXY motif in the integrin beta 3 subunit cytoplasmic tail for melanoma cell migration in vitro and in vivo.

The NPXY sequence is highly conserved among integrin beta subunit cytoplasmic tails, suggesting that it plays a fundamental role in regulating integrin-mediated function. Evidence is provided that the NPXY structural motif within the beta 3 subunit, comprising residues 744-747, is essential for cell morphological and migratory responses mediated by integrin alpha v beta 3 in vitro and in vivo. Transfection of CS-1 melanoma cells with a cDNA encoding the wild-type integrin beta 3 subunit, results in de novo alpha v beta 3 expression and cell attachment, spreading, and migration on vitronectin. CS-1 cells expressing alpha v beta 3 with mutations that disrupt the NPXY sequence interact with soluble vitronectin or an RGD peptide, yet fail to attach, spread, or migrate on immobilized ligand. The biological consequences of these observations are underscored by the finding that CS-1 cells expressing wild-type alpha v beta 3 acquire the capacity to form spontaneous pulmonary metastases in the chick embryo when grown on the chorioallantoic membrane. However, migration-deficient CS-1 cells expressing alpha v beta 3 with mutations in the NPXY sequence lose this ability to metastasize. These findings demonstrate that the NPXY motif within the integrin beta 3 cytoplasmic tail is essential for alpha v beta 3-dependent post-ligand binding events involved in cell migration and the metastatic phenotype of melanoma cells.

Amino Acid Sequence↗
PubMed1995

Induction of carcinoma cell migration on vitronectin by NF-kappa B-dependent gene expression.

Integrin alpha v beta 5 promotes FG carcinoma cell adhesion to vitronectin yet requires protein kinase C (PKC) activation for migration on this ligand. Here we report that this PKC-dependent cell motility event requires NF-kappaB-dependent transcription. Specifically, a component within nuclear extracts prepared from PKC-stimulated FG cells exhibited a significant increase in binding activity to a synthetic oligonucleotide containing a consensus kappa B sequence. These nuclear DNA-binding complexes were shown to be comprised of p65 and p50 NF-kappaB/rel family members and appeared functionally active because they promoted transcription of a reporter construct containing a kappa B site. The NF-kappa B activation event was directly linked to the alpha v beta 5 motility response because the NF-kappa B-binding oligonucleotide, when introduced into FG cells, inhibited cell migration on vitronectin but not on collagen and had no effect on cell adhesion to either ligand. These results suggest that the detected DNA-binding complexes interact with kappa B transcriptional elements to regulate gene expression required for alpha v beta 5-dependent cell motility on vitronectin.

Base Sequence↗
PubMed1994

A beta turn in the cytoplasmic tail of the integrin alpha v subunit influences conformation and ligand binding of alpha v beta 3.

Integrins undergo conformational alterations in response to extracellular or intracellular stimuli, suggesting that structural elements within their exo- and cytoplasmic domains cooperate during transmembrane signaling. In this report, we identify a beta turn in the cytoplasmic tail of the alpha v subunit that impacts the ligand binding and conformation of the alpha v beta 3 heterodimer. Cells expressing a mutant alpha v beta 3 heterodimer composed of a truncated alpha v subunit, alpha v1000, lacking 18 carboxyl-terminal amino acids exhibits wild-type receptor structure and function. However, a truncation mutant, alpha v995, lacking five additional residues (PPQEE), which define a beta turn, is deficient in vitronectin and fibrinogen adhesion. This alteration in adhesive function is associated with two detectable structural changes in the alpha v beta 3 heterodimer. First, the alpha v995 membrane-spanning light chain exhibits retarded electrophoretic mobility on SDS-polyacrylamide gels. Second, the alpha v995 beta 3 receptor shows an altered chymotryptic profile as measured by the loss of a 39-kDa proteolytic fragment from its ectodomain. These findings demonstrate that the ligand binding and structural properties of the intact alpha v beta 3 heterodimer can be influenced by a beta turn within the cytoplasmic tail of its alpha v subunit. The presence of homologous beta turns within other alpha subunit cytoplasmic tails suggests that this structural motif may play a role in regulating integrin-mediated bidirectional transmembrane signals.

Amino Acid Sequence↗
PubMed1994

Structural genes, not the LTRs, are the primary determinants of reticuloendotheliosis virus A-induced runting and bursal atrophy.

Reticuloendotheliosis virus strain A (REV-A) and chicken syncytial virus (CSV), two replication competent avian retroviruses, differ in the extent to which they induce a runting syndrome that includes anemia, lymphoid organ atrophy, and reduced body size. We have isolated an infectious clone of CSV, the less pathogenic of the two viruses, and compared it to REV-A. Partial DNA sequence analysis suggests that it differs from REV-A by no more than 1 to 2% at the nucleotide level. Analysis of viral interference indicates that these two viruses use the same cell receptor for infection of both fibroblasts and hematopoietic cells, DNA sequence of the CSV and REV-A long terminal repeats (LTRs) reveals that these structures differ principally by two small insertions (5 and 19 bp) present in the U3 region of REV-A. The larger of these may encode enhancer sequences that have been reported to influence transcription rates in vitro. Measurement of steady-state levels of viral RNA in infected cells, however, as well as circulating virus in infected chicks indicates that the different pathogenic responses elicited by these two viruses are not due to large differences in viral transcription or replication. Chimeric viruses were constructed in which the LTRs from one virus were used to express the structural genes of the second virus. Infection of 1-day-old chicks by parental virus as well as the reciprocal chimeric constructs demonstrated that the ability to induce both runting and bursal atrophy segregated with the structural genes of REV-A. Infection of birds with additional chimeric viruses in which the env genes of REV-A and CSV were exchanged indicated that the pathogenic response resulting from REV-A infection was due to at least two regions of the viral genome encoding structural genes.

Anemia↗
PubMed1994

Integrin alpha v beta 5 selectively promotes adenovirus mediated cell membrane permeabilization.

Human adenovirus type 2 (Ad2) enters host cells by receptor-mediated endocytosis, an event mediated by the virus penton base binding to cell surface integrins alpha v beta 3 and alpha v beta 5. While both alpha v integrins promote virus internalization, alpha v beta 5 is involved in the subsequent event of membrane permeabilization. Cells transfected with the beta 5 or beta 3 subunit, expressing either alpha v beta 5 and alpha v beta 3, respectively, were capable of supporting Ad2 infection to varying degrees. In this case, cells expressing alpha v beta 5 were significantly more susceptible to Ad2-induced membrane permeabilization, as well as to Ad2 infection, than cells expressing alpha v beta 3. Adenovirus-mediated gene delivery was also more efficient in cells expressing alpha v beta 5. These results suggest that the interaction of alpha v beta 5 with Ad2 penton base facilitates the subsequent step of virus penetration into the cell. These studies provide evidence for the involvement of a cellular receptor in virus-mediated membrane permeabilization and suggest a novel biological role for integrin alpha v beta 5 in the infectious pathway of a human adenovirus.

Adenoviruses, Human↗
PubMed1991

An avian retrovirus expressing chicken pp59c-myc possesses weak transforming activity distinct from v-myc that may be modulated by adjacent normal cell neighbors.

We demonstrate that EF168, an avian retrovirus that expresses the chicken pp59c-myc proto-oncogene, transforms quail embryo fibroblasts in vitro. An EF168-transformed quail clone, EF168-28, containing a single provirus, synthesizes several hundred copies of c-myc RNA and expresses elevated levels of the pp59c-myc gene product. The EF168 provirus in EF168-28 was isolated as a molecular clone, and the nucleotide sequence of its c-myc allele was confirmed as identical to that of exons 2 and 3 of the chicken c-myc proto-oncogene. Extended infection of quail embryo fibroblast cultures with EF168 induced a number of in vitro transformation-associated parameters similar to those elicited by the oncogenic v-myc-encoding retrovirus MC29, including alteration of cellular morphology, anchorage-independent growth, and induction of immortalized cell lines. Despite the fact that EF168 and MC29 shared these biological activities, further analysis revealed that EF168 initiated transformation in quail embryo fibroblasts, bone marrow, or adherent peripheral blood cultures 100- to 1,000-fold less efficiently than did MC29. Further, in contrast to MC29-induced foci, EF168 foci were smaller, morphologically diffuse, and less prominent. Analysis of newly infected cells demonstrated efficient expression of EF168 viral RNA in the absence of transformation. These differences suggest that while the pp59v-myc gene product can exert dominant transforming activity on quail embryo fibroblasts, its ability to initiate transformation is distinct from that of the pp110gag-v-myc gene product encoded by MC29 and may be suppressed by adjacent nontransformed cell neighbors.

Animals↗