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M Jalkanen

Publications and source records attributed to M Jalkanen.

At least 55 records · Page 3Linked to original sources
PubMed1994

A novel laminin-binding form of syndecan-1 (cell surface proteoglycan) produced by syndecan-1 cDNA-transfected NIH-3T3 cells.

Syndecan-1, a cell surface proteoglycan, binds many extracellular matrix components via its heparan sulfate side chains. In previous studies syndecan-1 has failed to bind laminin, although both syndecan-1 and laminin are expressed at sites of early matrix accumulation, like in basement membranes of epithelial-mesenchyma boundaries and in condensing mesenchymes during embryonic development. In order to study whether syndecan-1 regulates the adhesion of mesenchymal cells to laminin, syndecan-1 was expressed in NIH-3T3 cells by transfection. Syndecan-1-transfected cells showed increased binding to laminin in comparison to control transfected cells. We then compared the properties of syndecan-1 isolated from transfected NIH-3T3 cells and from NMuMG mammary epithelial cells. In solid-phase binding assays, syndecan-1 from NIH-3T3 cells, but not NMuMG cells, bound to laminin. NIH-3T3-derived syndecan contained more chondroitin sulfate than NMuMG-derived syndecan-1, and our results revealed that both heparan sulfate and chondroitin sulfate mediate syndecan-1 binding to laminin. E3 domain revealed highest binding for syndecan-1 among the elastase-derived fragments of laminin. These results suggest that induction of syndecan-1 in mesenchymal cells may be involved in cellular recognition of laminin during developmental processes.

3T3 Cells↗
PubMed1994

Association between syndecan-1 expression and clinical outcome in squamous cell carcinoma of the head and neck.

Syndecans are a family of cell-surface heparan sulphate proteoglycans which are involved in cell-matrix interactions and growth factor binding. Syndecan-1 binds basic fibroblast growth factor (bFGF) and several components of the extracellular matrix. Syndecan-1 expression is induced during keratinocyte differentiation and reduced during the formation of squamous cell carcinomas (SCCs). The purpose of this study was to examine the association of syndecan-1 expression with prognostic factors and clinical outcome in SCC of the head and neck. Frozen sections of 29 primary SCCs were analysed for syndecan-1 expression using immunohistochemical methods. Intermediate or strong staining for syndecan-1 was associated with a smaller primary tumour size (P = 0.0005) and higher histological grade of differentiation (P = 0.006) than negative or weakly positive staining. In a univariate analysis, syndecan-1-positive tumours were associated with higher overall (P = 0.001) and recurrence-free survival (P = 0.003) than those tumours with no or little syndecan-1 expression. The results suggest that syndecan-1 could be an important prognostic factor of SCC of the head and neck. Further studies on the prognostic significance of syndecan-1 expression in SCCs are warranted.

Adult↗
PubMed1994

Analysis of transport and targeting of syndecan-1: effect of cytoplasmic tail deletions.

Madin-Darby canine kidney (MDCK) cells and Chinese hamster ovary (CHO) cells were transfected with wild-type and cytoplasmic deletion mutants of mouse syndecan-1 to study the requirements for transport and polarized expression of this proteoglycan. Expression in MDCK cells revealed that wild-type syndecan-1 is directed to the basolateral surface via a brefeldin A-insensitive route. A deletion of the last 12 amino acids of the syndecan-1 cytoplasmic tail (CT22) was sufficient to result in the appearance of mutant proteoglycans at both the basolateral and apical cell surfaces. Treatment with brefeldin A was able to prevent apical transport of the mutants. We thus propose that the C-terminal part of the cytoplasmic tail is required for steady-state basolateral distribution of syndecan-1. In CHO cells a deletion of the last 25 or 33 amino acids of the 34-residue cytoplasmic domain (CT9 and CT1, respectively) resulted in partial retention of the mutants in the endoplasmic reticulum (ER). A deletion mutant lacking the last 12 amino acids (CT22) was not retained. Interestingly, the unglycosylated core proteins of the CT9 and CT1 mutants showed a significantly lower apparent molecular weight when analyzed by sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis than wild-type syndecan-1. However, when CHO transfectants expressing the CT1 mutant were incubated with brefeldin A, causing fusion of the ER and Golgi, CT1 ran with an almost equally high apparent molecular weight as the wild-type molecule. This would suggest that syndecan-1 undergoes extensive posttranslational modifications or forms an SDS-resistant dimer/complex after transit from the ER.

Amino Acid Sequence↗
PubMed1994

The cytoplasmic domain of syndecan-1 is not required for association with Triton X-100-insoluble material.

Cell surface heparan sulfate proteoglycans such as syndecan-1 bind various extracellular matrix proteins and have been suggested to interact with the cytoskeleton. Such interactions are thought to be important for stabilizing cell morphology. Syndecan-1 resists extraction with Triton X-100. This insolubility was reported not to be affected by removal of the glycosaminoglycan chains, suggesting that the insolubility is not due to binding to the extracellular matrix, but rather to an association with the actin cytoskeleton (Rapraeger, A., Jalkanen, M. and Bernfield, M. (1986) J. Cell Biol. 103, 2683-2696). To examine further the interaction of syndecan-1 with the Triton X-100-insoluble residue, we expressed wild-type mouse syndecan-1 and a cytoplasmic deletion mutant (tail-less) in Chinese hamster ovary cells. We observed that both the wild-type and the tail-less syndecan-1 were partly insoluble in Triton X-100. The insolubility was not affected by increasing temperature (37 degrees C or 50 degrees C) or by cytochalasin D. Removal of the glycosaminoglycan chains from the ectodomain, however, resulted in complete Triton X-100 solubility, unlike previous reports. Syndecan-1 could also be released into the Triton X-100-soluble fraction by addition of heparin or heparan sulfate to the extraction medium. We conclude that the cytoplasmic domain of syndecan-1 is not responsible for Triton X-100 insolubility. Instead, our results indicate that Triton X-100 insolubility is caused by an interaction of syndecan-1 molecules with other cellular and/or extracellular molecules mediated by the heparan sulfate chains.

Animals↗
PubMed1994

[Anders Jahre Prize for young researchers 1993. Syndecan--a regulator of growth factor activities between cells and cell matrix interface].

Syndecans are a four member family of cell surface proteoglycans, which via their heparan sulfate chains can bind both extracellular matrix molecules and heparin-binding growth factors. In signal transduction they cooperate with tyrosine kinase receptors and thus can participate in the regulation of cell growth and behaviour. Besides the fact that their developmental expression follows morphogenetic rather than histological boundaries, also changes in their expression take place during development of diseases. Among these, the loss of syndecan expression during malignant transformation suggests that syndecans could play a role in restricting tumor growth and metastasis.

Awards and Prizes↗
PubMed1994

Expression of syndecan-1 is induced by differentiation and suppressed by malignant transformation of human keratinocytes.

Syndecans comprise a family of integral membrane proteoglycans that presumably participate in cell-matrix interactions and the modulation of growth factor response. Expression of syndecan-1, a cell surface proteoglycan that binds basic fibroblast growth factor (bFGF) and extracellular matrix components, was studied in cultured human keratinocytes from the oral mucosa and in tissue sections derived from various epithelia and carcinomas of the head and neck. For the study, polyclonal antibodies were raised against the core protein of human syndecan-1. The affinity-purified antibody (designated anti-P117) was shown to react specifically with syndecan-1. Abundant expression of syndecan-1 was detected in frozen sections of various stratified epithelia as well as in cultured keratinocytes. Keratinocytes located in the spinous cell layers showed intense immunoreactivity for syndecan-1, while basal cells stained rather weakly, suggesting that the expression of syndecan-1 could be stimulated during the differentiation of keratinocytes. Cultured human keratinocytes were induced to terminally differentiate by increasing the extracellular calcium concentration of the medium. Parallel to the induction of involucrin expression, the mRNA levels of syndecan-1 were found to increase, suggesting that syndecan-1 is indeed induced during keratinocyte differentiation. The molecular mass and glycosaminoglycan composition of syndecan-1 did not change markedly during calcium-induced differentiation. Malignant transformation was associated with marked reduction of syndecan-1 expression, based on the immunoreactivity of anti-P117 in frozen sections from squamous cell carcinomas (SCCs) of the head and neck.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1993

Inhibition of basic fibroblast growth factor-induced growth promotion by overexpression of syndecan-1.

The expression of syndecan-1, the prototype member of the cell surface proteoglycan family, follows morphogenetic rather than histological boundaries during organ formation. As a heparan sulfate-containing cell surface molecule, syndecan-1 can simultaneously bind various components of the extracellular matrix and members of the heparin-binding growth factors. Indeed, syndecan-1 may act as a co-receptor for basic fibroblast growth factor (bFGF) (Salmivirta, M., Heino, J., and Jalkanen, M. (1992) J. Biol. Chem. 267, 17606-17610), allowing the growth factor to bind the tyrosine kinase bFGF receptor. We have studied the role of syndecan-1 in growth factor response by growing 3T3 cells transfected with syndecan-1 in the presence of bFGF. The enhanced expression of syndecan-1 caused down-regulation of bFGF-induced cell proliferation and, at the same time, enhancement of cell matrix interactions. Thus, the induced expression of the heparan sulfate co-receptor (syndecan-1) may provide a mechanism to restrict FGF action and modulate cell-matrix interactions to maintain co-ordinated growth of cells during organ formation.

3T3 Cells↗
PubMed1993

Structural organization and genomic sequence of mouse syndecan-1 gene.

Syndecan-1 is an integral membrane proteoglycan, which binds several extracellular matrix components and growth factors. Its expression follows morphogenetic rather than histological patterns during embryonic development and is regulated by epithelial-mesenchymal interactions during organogenesis. Malignant transformation has been shown to suppress syndecan-1 expression. In order to understand better the regulation of syndecan-1 expression, we have determined the structural organization of mouse syndecan-1 gene. Several genomic clones were isolated, covering the entire 23-kilobase (kb) syndecan-1 gene. All five exons, four introns, and the 5'- and 3'-flanking regions were sequenced. The first intron was very long (17,582 base pairs (bp)) if compared with the others that were only a few hundred nucleotides in length. The first exon contained only the signal sequence and exons II-IV all the glycosaminoglycan binding sites. The fifth exon resided both transmembrane and cytoplasmic domains, which are known to be conserved among the members of the syndecan family. This genomic structure explains why these members could have heterologous extracellular domains and homologous transmembrane and cytoplasmic domains. Syndecan-1 gene was shown by primer extension analysis to have three transcription initiation sites which were confirmed by polymerase chain reaction. These initiation sites were found to locate -217, -266, and -591 bp from described cDNA (Saunders, S., Jalkanen, M., O'Farrell, S., and Bernfield, M. (1989) J. Cell Biol. 108, 1547-1556). Within the 5'-end of the gene a 2000-bp-long CpG nucleotide-rich sequence resembling a CpG island was found, which started from the transcription initiation sites and ended in the first intron. At the 3'-end of the gene an other polyadenylation signal sequence was revealed 638 bp downstream from the first one. The two mRNAs (2.6 kb and 3.4 kb) were shown to be produced by alternative polyadenylation.

3T3 Cells↗
PubMed1993

Accumulation of heavy metals in the mole in Finland.

Metal concentrations (Cu, Ni, Zn, Cd, Cr, Hg, Pb and Mo) were analysed from the liver and kidneys of moles, Talpa europaea L. (Insectivora), trapped in southern Finland on both contaminated and rural areas. In rural areas the concentrations of Cd, Cu, Zn, Pb and Mo were lower in juveniles (individuals in their first summer), except for Zn in the liver, which was lower in adults. When the animals were divided into annual classes (0-6 years), Cd and Mo concentrations in the liver increased significantly with age, while concentrations of Cu, Zn and Cr tended to decrease. Female moles had higher Pb concentrations than males, especially adult females, which also had lower levels of Cu in the liver than adult males. Moles in the metropolitan area of Helsinki clearly differed from those in rural areas in that the concentrations of heavy metals in these moles were higher (especially for the most toxic metals: Cd, Pb and Hg), and their body weight was lower. The renal concentrations of Cd in most of the moles in Helsinki exceeded the threshold that has been shown to have a nephrotoxic effect in mammals. In one subsample from Helsinki, Pb and Zn concentrations in the mole liver decreased as the distance from the highway increased. Concentrations of Pb in earthworms and several heavy metals in soil also decreased similarly in the same area. Our data indicate that Pb accumulates in moles through their diet of earthworms.

Journal Article↗
PubMed1993

Translational suppression of syndecan-1 expression in Ha-ras transformed mouse mammary epithelial cells.

A cell surface proteoglycan, syndecan-1, has been shown to participate in the maintenance of the epithelial cell morphology. A point mutated activated c-Ha-ras gene under the control of the glucocorticoid inducible MMTV-LTR promoter was transfected into the mouse mammary epithelial cell line, NOG-8. The NOG-8 ras cells were used to study changes in syndecan-1 expression during epithelial transformation. NOG-8 ras cells, when induced to express Ha-ras, transformed and formed foci in monolayer cultures and colonies in suspension cultures. Expression of syndecan-1 at the cell surface was markedly reduced in cells showing the transformed phenotype. The accumulation of newly synthesized core protein of syndecan-1 was suppressed in these cells, whereas mRNA levels remained unchanged. This novel finding indicates that syndecan-1 expression is translationally suppressed in the Ha-ras-transformed epithelial cells. Hence, syndecan-1 loss during epithelial transformation could take place without altering syndecan gene transcription and, on the other hand, could be one of the critical events involved in malignant transformation.

Animals↗
PubMed1993

Expression of integrin family of cell adhesion receptors in rheumatoid synovium. Alpha 6 integrin subunit in normal and hyperplastic synovial lining cell layer.

Integrins are heterodimeric cell adhesion receptors. The beta 1 integrin subunit can be in a complex with multiple a subunits and form receptors for collagen, laminin, fibronectin, and vitronectin. We have characterized the distribution of eight integrin subunits in rheumatoid synovium, with special interest in the lining cell layer. The beta 1 integrin subunit was found in abundance in synovial stroma and in lining cells. The only alpha subunit seen constantly in lining cells was alpha 6. In complex with alpha beta subunit, alpha 6 forms a laminin receptor usually seen in epithelial or endothelial cells or in macrophages. The fact that laminin was found in the extracellular matrix around synovial cells suggests the importance of alpha 6 integrin in the adhesion of synovial lining cells. Furthermore, alpha 6 expression was noticeably weaker in strongly proliferative lining cell layers, indicating that the inflammatory process may regulate integrin expression. A potential connection between altered expression of cell adhesion receptors and the pathological behavior of rheumatoid lining cells is suggested.

Adolescent↗
PubMed1992

Enhanced expression of the tie receptor tyrosine kinase in endothelial cells during neovascularization.

We have recently cloned a novel human receptor tyrosine kinase, tie, from human leukemia cells showing megakaryoblastoid differentiation. We report here that the 4.4-kb tie messenger RNA (mRNA) is present in all human fetal and mouse embryonic tissues. By in situ hybridization, the tie mRNA was localized to the endothelia of blood vessels and endocardium of 9.5- to 18.5-day mouse embryos. However, tie was not expressed by endothelial cells of developing hepatic sinusoids. Increased tie mRNA signal was seen in proliferating ovarial capillaries during hormone-induced superovulation. Only a weak tie signal was obtained from adult skin, except during wound healing, when the proliferating capillaries in the granulation tissue contained abundant tie RNA. These results suggest that tie may have a role in neovascularization.

Amino Acid Sequence↗
PubMed1992

Basic fibroblast growth factor-syndecan complex at cell surface or immobilized to matrix promotes cell growth.

Promotion of cell growth and differentiation by growth factors during early development and organ formation are both temporally and spatially very precise. Syndecan is a well characterized integral membrane proteoglycan that binds several extracellular matrix components via its heparan sulfate chains and is therefore suggested to participate in cell regulation. Syndecan-like molecules, as low affinity receptors for heparin-binding growth factors, have been recently suggested to also regulate growth factor activity. Heparin/heparan sulfate interaction is required before, e.g. basic fibroblast growth factor (bFGF) can associate with its high affinity cell surface receptors and trigger signal transduction. In this paper we show that syndecan, but not free heparan sulfate chains, can simultaneously bind both bFGF and extracellular matrix molecules. Moreover, increased DNA synthesis of 3T3 cells was observed when the 3T3 cells were exposed to beads coated with the fibronectin-syndecan-bFGF complex, indicating that bFGF remains biologically active even when immobilized to matrix via the heparan sulfate chains of syndecan. Finally, when bFGF was bound to the surface of another cell type (epithelial), co-culture with 3T3 cells stimulated 3T3 cell growth. Therefore, we suggest that syndecan-like molecules may determine sites of growth factor action at cell-matrix and cell-cell interfaces.

3T3 Cells↗
PubMed1992

Growth factors induce 3T3 cells to express bFGF-binding syndecan.

Syndecan is an integral membrane proteoglycan that putatively binds extracellular matrix molecules and growth factors at the surfaces of several cell types. Syndecan is also transiently expressed in several condensing mesenchymes after epithelial induction. In order to understand the mechanism(s) that regulate(s) syndecan expression in early mesenchymal cells, we have studied the effects of growth factors on the expression of syndecan in 3T3 fibroblasts and compared these results to NMuMG epithelial cells. Our studies indicate that (i) two developmentally important growth factors, basic fibroblast growth factor (bFGF) and transforming growth factor beta (TGF-beta), especially when administrated at the same time, increase syndecan expression in 3T3 cells both at the mRNA and protein level. (ii) Furthermore, the same growth factors also increase syndecan shedding into the culture medium of 3T3 cells. No such stimulation of syndecan synthesis or shedding was observed with NMuMG cells. (iii) Syndecan isolated from the cell surface of bFGF+TGF-beta-treated 3T3 cells binds bFGF. (iv) Induced expression of syndecan correlates with enhanced binding of bFGF to the cell surface of 3T3 cells, and (v) this interaction can be inhibited by exogenous ectodomain of syndecan. These results suggest a key role for growth factors in the regulation of syndecan expression during organogenesis and, moreover, an involvement of syndecan in the regulation of growth factor action.

3T3 Cells↗
PubMed1992

Stable expression of recombinant human alpha 2-adrenoceptor subtypes in two mammalian cell lines: characterization with [3H]rauwolscine binding, inhibition of adenylate cyclase and RNase protection assay.

Cloning of the genes encoding distinct subtypes of human alpha 2-adrenergic receptors (alpha 2-AR) allows the separate recombinant expression of each individual subtype in heterologous systems. We report here the transfection, selection and preliminary pharmacological characterization of two mammalian cell lines, adherent Shionogi S115 mouse mammary tumour cells and human B-lymphoblastoid IBW4 cells growing in suspension, expressing the human alpha 2-AR subtypes alpha 2-C4 and alpha 2-C10 at densities of approx. 2 x 10(5) receptors/cell. Transfection of the subtype genes was verified using a specific RNase protection assay. Pharmacological characterization was carried out with [3H]rauwolscine binding, which was inhibited by oxymetazoline and prazosin in a subtype-selective manner. The sensitivity of (-)-noradrenaline binding to the GTP-analogue 5'-guanylylimidodiphosphate suggested that the receptors are coupled to G-proteins. This was verified in S115 cells by efficient inhibition of forskolin-stimulated cAMP production by the alpha 2-AR agonists, (-)-noradrenaline and clonidine. These cell lines thus appear to be suitable for pharmacological studies on receptor function and ligand binding.

Adenylyl Cyclase Inhibitors↗
PubMed1992

Syndecan expression regulates cell morphology and growth of mouse mammary epithelial tumor cells.

S115 mouse mammary epithelial cells lose their epithelial morphology and become tumorigenic when exposed to steroids. We have recently reported that testosterone exposure results in the suppression of syndecan expression, suggesting that this cell surface proteoglycan may influence S115 cell phenotype. We now report that a similar suppression and morphological response of S115 cells can be achieved by glucocorticoid exposure. We introduced into S115 cells an exogenous gene construct containing the full-length human syndecan cDNA under the control of a glucocorticoid-inducible retroviral promoter, in order to study the effect of syndecan expression on S115 cell behavior. Glucocorticoid-induced re-expression of syndecan in S115 cells restored an epithelial phenotype, while control transfectants and parental S115 cells exhibited an altered, nonepithelial phenotype. Moreover, the S115 cells expressing exogenous syndecan revealed a reduced ability to form colonies in soft agar. Therefore, the maintenance of epithelial morphology and normal growth of S115 cells are dependent on syndecan expression.

Actin Cytoskeleton↗