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Biomedical subjects

E Engvall

Publications and source records attributed to E Engvall.

At least 73 records · Page 4Linked to original sources
PubMed1991

Expression of beta 4 integrins in human skin: comparison of epidermal distribution with beta 1-integrin epitopes, and modulation by calcium and vitamin D3 in cultured keratinocytes.

The expression of beta 4 integrins in adult and fetal human skin as well as in cultured keratinocytes was studied by immunodetection with monoclonal antibodies, and compared with that of beta 1 integrins. The distribution of the beta 1 and beta 4 integrin epitopes was entirely different in the adult epidermis. As reported previously by us (J Clin Invest 84:1916, 1989), the beta 1 epitopes were present most prominently at lateral cell-cell contact points, whereas staining with the beta 4 antibody demonstrated a linear staining pattern polarizing to the basal surface juxtaposed to the dermal-epidermal basement membrane. In contrast, in fetal skin, the staining patterns both with beta 1 and beta 4 antibodies were similar and demonstrated the presence of epitopes surrounding the entire cell surface of both basal and suprabasal keratinocytes. Distinct polarization of beta 4 integrin epitopes was noted in cultured keratinocytes maintained in low-calcium (0.15 mM) medium, and the expression of these integrins was also noted in human papilloma virus-transformed keratinocytes. Switch of the cultures to high-calcium (1.2 mM) medium resulted in redistribution of the epitopes to a pattern suggesting their location at under-surface of the cells adjacent to the substratum. This Ca(++)-induced redistribution of beta 4 integrin epitopes could be counteracted by 10(-7) M vitamin D3. Finally, incubation with anti-beta 4 integrin antibody reduced the capacity of keratinocytes to attach to plastic substratum. The results provide further evidence for the role of beta 4 integrins in cell-matrix interactions.

Adult↗
PubMed1990

Merosin, a tissue-specific basement membrane protein, is a laminin-like protein.

Merosin is a basement membrane-associated protein found in placenta, striated muscle, and peripheral nerve. A 3.6-kilobase merosin cDNA clone was isolated from a placental cDNA expression library. The clone contained a 3.4-kilobase open reading frame, the 3' portion of which includes protein sequences of proteolytic fragments of merosin. The deduced amino acid sequence of the merosin polypeptide was similar to that of the COOH-terminal region of the 400-kDa A chain of laminin. This part of laminin forms the large globule at the end of the long arm of the laminin cross and is thought to contain the neurite-promoting site and the major cell binding site(s) in laminin. The sequence identity between merosin and the laminin A chain in this region is nearly 40%. An antiserum against a synthetic peptide from the middle of the merosin cDNA sequence identified a 300-kDa polypeptide in placental extracts, indicating that the merosin polypeptide is similar in size to the laminin A chain. Intact merosin was isolated from placental extracts and shown to be covalently associated with the laminin B chains and to have a cross-like structure similar to that of laminin. The similarities between merosin and laminin show that both proteins are members of the same family of basement membrane proteins.

Amino Acid Sequence↗
PubMed1990

Molecular heterogeneity of basal laminae: isoforms of laminin and collagen IV at the neuromuscular junction and elsewhere.

Laminin and collagen IV are components of most basal laminae (BLs). Recently, both have been shown to be products of multigene families. The A, B1, and B2 subunits of the laminin trimer are products of related genes, and the BL components merosin M and s-laminin are homologues of the A and B1 subunits, respectively. Similarly, five related collagen IV chains, alpha 1(IV)-alpha 5(IV), have been described. Here, we used a panel of subunit-specific antibodies to determine the distribution of the laminin and collagen IV isoforms in adult BLs. First, we compared synaptic and extrasynaptic portions of muscle fiber BL, in light of evidence that axonal and muscle membranes interact selectively with synaptic BL during neuromuscular regeneration. S-laminin, laminin A, and collagens alpha 3(IV) and alpha 4(IV) are greatly concentrated in synaptic BL; laminin B1 is apparently absent from synaptic BL; collagens alpha 1(IV) and alpha 2(IV) are less abundant in synaptic than extrasynaptic BL; and laminin B2 and merosin M are present at similar levels synaptically and extrasynaptically. These results reveal widespread differences between synaptic and extrasynaptic BL, and implicate several novel polypeptides as candidate mediators of neuromuscular interactions. Second, we widened our inquiry to assess the composition of several other BLs: endoneurial and perineurial BLs in intramuscular nerves, BLs associated with intramuscular vasculature, and glomerular and tubular BLs in kidney. Of eight BLs studied, at least seven have distinct compositions, and of the nine BL components tested, at least seven have distinct distributions. These results demonstrate a hitherto undescribed degree of heterogeneity among BLs.

Adolescent↗
PubMed1990

Distribution and isolation of four laminin variants; tissue restricted distribution of heterotrimers assembled from five different subunits.

The distribution of subunits of the basement membrane proteins laminin and merosin in human and rabbit tissue was studied by immunofluorescence using monoclonal antibodies. The laminin A chain is present in epithelial, endothelial, and smooth muscle basement membranes. Merosin, as defined by its heavy chain M, is present in striated muscle and peripheral nerve. The A subunit colocalizes with at least two B subunits: B2 plus either B1 or the recently discovered B1 homologue S. The M subunit most often colocalizes with B1 and B2. Exceptions include the myotendinous junction, where M colocalizes with S, and the trophoblast basement membrane, where the M subunit colocalizes with S as well as B1. The presence of all five known subunits of the laminin family in placenta allowed isolation of their parent molecules in native form by the use of monoclonal antibodies in affinity chromatography. Four different heterotrimeric proteins could be identified: B1 chain-containing laminin (A-B1-B2), S chain-containing laminin (A-S-B2), B1-containing merosin (M-B1-B2), and S-containing merosin (M-S-B2). The data show that the proteins in the laminin family are heterotrimers composed of one heavy and two light chains; that most basement membranes contain predominantly one protein of the laminin family; and that laminin, as defined by the A subunit, has a much more restricted distribution than previously thought.

Animals↗
PubMed1990

Fibrillin immunoreactive fibers constitute a unique network in the human dermis: immunohistochemical comparison of the distributions of fibrillin, vitronectin, amyloid P component, and orcein stainable structures in normal skin and elastosis.

Fibrillin, a 350-kD glycoprotein, was recently localized to elastin-associated 10 nm microfibrils. Here, the distribution of fibrillin immunoreactivity was determined in normal skin in individuals of different ages and in lesions of solar elastosis or anetoderma. It was compared with the distribution of orcein-stainable fibers and with the immunoreactivities of vitronectin and amyloid P component. These glycoproteins are known to occur in conjunction with the orcein-stainable elastic fibers in adults, but not in the young. Fibrillin immunoreactivity was associated with orcein-stainable fibers in normal skin of both adults and the young. In addition, the fibrillin immunoreactive fiber network comprised fine fibers that were unstainable by orcein, anti-vitronectin, or anti-amyloid P component. Such fine fibers were especially abundant close to the dermal-epidermal junction zone. Immunoreactivities of anti-vitronectin and anti-amyloid P component were not always associated with fibrillin immunoreactivity but were consistently found to co-localize with orcein-stainable fibers in adults. This suggests vitronectin and amyloid P component to be associated with the amorphous elastin rather than with the microfibrils, although alternative interpretations are possible. In elastotic lesions, fibrillin immunoreactivity was generally fainter than that obtained using anti-vitronectin or anti-amyloid P component. In contrast, an extensive network of dermal fibers stained by anti-fibrillin, but not by anti-amyloid P component, anti-vitronectin, or orcein, was seen in an anetoderma lesion. In conclusion, fibrillin immunoreactivity is associated with a unique dermal network, which ultrastructurally is composed of microfibrils. These fibers are proposed to have an important structural and functional role in anchoring the dermal elastic fibers in the extracellular matrix and to the lamina densa.

Connective Tissue Diseases↗
PubMed1989

Subunit structure of a laminin-binding integrin and localization of its binding site on laminin.

A laminin receptor was isolated from human MG-63 osteosarcoma cells by affinity chromatography on human laminin. The isolated receptor was defined as the alpha 3 beta 1 integrin by immunoprecipitation with subunit-specific antibodies. A previously unclassified laminin-binding integrin from rat cells was shown also to contain the alpha 3 subunit. Both receptors bound to human and mouse laminin in a radioreceptor assay. They also both bound to some extent to fibronectin in this assay, but only the MG-63 cell receptor showed binding to type IV collagen. The binding of the radiolabeled receptor to insoluble laminin was inhibited by unlabeled receptor, by soluble laminin, and by chymotryptic fragments of laminin that have previously been shown to contain neurite-promoting and cell attachment-promoting activities. Moreover, the receptor binding was also inhibited by monoclonal antibodies capable of inhibiting the neurite-promoting activity of laminin and known to bind to laminin near the junction of the long arm and its terminal globule. One of these antibodies was reactive with fusion proteins expressed from laminin cDNA clones. The immunoreactive clones corresponded to the COOH-terminal end of the B1 subunit. These results identify the integrin-type laminin receptor isolated from the osteosarcoma cells as the alpha 3 beta 1 integrin and localize its binding site in close proximity of the B1 subunit COOH terminus.

Binding Sites↗
PubMed1989

Laminin-like antigen in rat CNS neurons: distribution and changes upon brain injury and nerve growth factor treatment.

Using several antibodies against rat or human laminin and an avidin-biotin immunocytochemical protocol, laminin-like immunoreactivity was detectable in the rat nervous system in expected locations, i.e., associated with blood vessels and reactive astrocytes. However, laminin staining was also abundantly present within neuronal cell bodies in most parts of the developing and adult rat CNS. Medial septum neuronal immunoreactivity was lost after septo-hippocampal disconnection, but could be preserved or even restored by intraventricular administration of nerve growth factor. Thus, at least for medial septum neurons, this laminin-like molecule can be accumulated or produced independent of direct hippocampal (target) contact. It remains to be determined whether CNS neuronal "laminin" processes activities similar to those found for laminin in vitro.

Aging↗
PubMed1989

Schwannoma cell-derived inhibitor of the neurite-promoting activity of laminin.

During the purification of laminin-proteoglycan complexes from rat RN22 Schwannoma cell-conditioned medium, a laminin-rich fraction was obtained which lacked neurite-promoting activity. Since laminin from several sources is known to have potent neurite-promoting activity, this result suggested that either this laminin was inactive or its activity was somehow masked by associated molecule(s). The latter possibility was supported by the demonstration that the inactive laminin-containing fraction inhibited active laminin-containing fractions. This inhibitory activity was partially purified by using ion exchange chromatography and isopycnic centrifugation. The purified material contained proteoglycan based on its high affinity for cationic resin, high buoyant density, large heterodisperse appearance on electrophoretic gels, ability to label with inorganic sulfate, sensitivity to trypsin and glycosaminoglycan lyases, and heat stability. A quantitative in vitro bioassay was used to monitor the inhibitor after treatments aimed at defining its activity. The isolated Schwannoma-derived inhibitor (a) inhibits the neurite-promoting activity of purified rat, mouse, and human laminin; (b) is active whether presented to laminin in solution or after either the inhibitor or laminin is first bound to the culture substratum; (c) does not act by displacing laminin from the substratum; (d) can be prevented from binding to neurite-promoting laminin substrates by polyclonal and monoclonal anti-laminin or polyclonal anti-entactin antibodies; and (e) is abolished by proteases or glycosaminoglycan lyases but not by heat. The above results suggest that the neurite-promoting activity of laminin is subject to regulation through association with a proteoglycan and entactin.

Animals↗
PubMed1989

Endothelial cells use alpha 2 beta 1 integrin as a laminin receptor.

Human umbilical vein endothelial cells attach and spread on laminin-coated substrates. Affinity chromatography was used to identify the attachment receptor. Fractionation of extracts from surface-iodinated endothelial cells on human laminin-Sepharose yielded a heterodimeric complex, the subunits of which migrated with molecular sizes corresponding to 160/120 kD and 160/140 kD under nonreducing and reducing conditions, respectively. The purified receptor bound to laminin and slightly less to fibronectin and type IV collagen in a radioreceptor assay. This endothelial cell laminin receptor was classified as an alpha 2 beta 1 integrin because monoclonal and polyclonal antibodies directed against the alpha 2 and bet 1 subunits immunoprecipitated the receptor. Cytofluorometric analysis and immunoprecipitation showed that the alpha 2 subunit is an abundant integrin alpha subunit in the endothelial cells and that the alpha subunits associated with laminin binding in other types of cells are expressed in these cells only at low levels. The alpha 2 beta 1 integrin appears to be a major receptor for laminin in the endothelial cells, because an anti-alpha 2 monoclonal antibody inhibited the attachment of the endothelial cells to human laminin. These results define a new role for the alpha 2 subunit in laminin binding and suggest that the ligand specificity of the alpha 2 beta 1 integrin, which is known as a collagen receptor in other types of cells, can be modulated by cell type-specific factors to include laminin binding.

Animals↗
PubMed1989

Expression of merosin, a tissue-specific basement membrane protein, in the intermediate trophoblast cells of choriocarcinoma and placenta.

Merosin is a novel tissue-specific basement membrane-associated protein found in basement membranes of trophoblast, striated muscle and Schwann cells. In placental extracts, the immuno-reactivity for merosin was detected in a protein band of 80 kilodaltons, and a 65 kilodalton polypeptide fragment of merosin could be isolated from proteolytic digests of placenta. In the present study, we describe the expression of merosin in human choriocarcinomas and normal placentas using immunoperoxidase staining of paraffin-embedded tissues. All five choriocarcinomas studied show immunoreactivity for merosin. Tumor cells, exhibiting the morphology typical of the intermediate trophoblast, stained distinctly for merosin. The cytotrophoblast and syncytiotrophoblast cells in these tumors showed negligible or no staining. In second and third trimester human placentas, merosin immunoreactivity was found in large extravillar mononuclear trophoblast cells of the basal plate as well as in the trophoblast basement membranes of the chorionic villi. The results indicate that merosin is mainly expressed in the intermediate trophoblast cells of both neoplastic and normal origin, whereas almost no expression is seen in cytotrophoblast and syncytiotrophoblast. Consequently, it is suggested that the intermediate trophoblast may represent a third, independently differentiated trophoblastic cell type.

Antibodies, Monoclonal↗
PubMed1989

Distribution of merosin, a laminin-related tissue-specific basement membrane protein, in human Schwann cell neoplasms.

The expression of merosin and laminin was studied in human schwannomas, plexiform neurofibromas, and malignant schwannomas immunohistochemically using monoclonal antibodies. Merosin is a unique novel tissue-specific basement membrane protein found in basement membranes of trophoblast, striated muscle, and Schwann cells. Merosin is related to laminin, another basement membrane protein with which it shows a homologous C terminal domain. In schwannomas, merosin was only found in areas where tumor cells were in contact with stromal or vascular tissue. Laminin, however, was present in all tumor cell basement membranes. In plexiform neurofibromas large amounts of both merosin and laminin were seen in Schwann cell basement membranes. Very little of either protein was found in malignant schwannomas. Thus merosin is present almost exclusively in highly differentiated Schwann cell neoplasms, and its distribution is more restricted than that of laminin. The expression of merosin in plexiform neurofibromas and in the schwannoma cells juxtaposed to the mesenchymal cells suggests that this protein is induced epigenetically in well-differentiated cells in contact with connective tissue or vascular components.

Adult↗
PubMed1988

The human laminin receptor is a member of the integrin family of cell adhesion receptors.

A receptor for the adhesive basement membrane protein, laminin, was isolated from human glioblastoma cells by affinity chromatography on laminin. This receptor has a heterodimeric structure similar to that of receptors for other extracellular matrix proteins such as fibronectin and vitronectin. Incorporation of the laminin receptor into liposomal membranes makes it possible for liposomes to attach to surfaces coated with laminin. The receptor liposomes also attached to some extent to surfaces coated with fibronectin, but not with other matrix proteins. These properties identify the laminin receptor as a member of the integrin family of cell adhesion receptors.

Antigens, Surface↗
PubMed1988

Rat amnion membrane matrix as a substratum for regenerating axons from peripheral and central neurons: effects in a silicone chamber model.

An extracellular matrix preparation, the human amnion membrane matrix (hAMM) can serve as a neurite-promoting substratum for cultured peripheral and central neurons, and also as a support for axonal growth in experimentally injured adult brain in vivo. In the present study, we tested similar materials as bridges in a silicone chamber model for the regeneration of sciatic nerve in the adult rat. Since hAMM elicited an inflammatory response, we developed a rat amnion membrane matrix (rAMM), which proved to be an excellent neurite-promoting substratum for cultured ganglionic and spinal cord neurons. The rAMM was coiled and inserted in the 10 mm gap between the two nerve stumps from the silicone chambers. At 16 days after implantation, temporal progress of regeneration was grossly similar as in saline-prefilled control chambers. However, rAMM-prefilled chambers displayed significantly higher number of vessels and a markedly different geometry of the regenerate: an endoneurium, surrounded by a perineurial-like cell layer, was formed outside the largely preserved central portion of the rAMM coil. After longer regeneration times (28 days), a rAMM core was no longer detected, but some rAMM-like materials remained interspersed in the endoneurium. The overall organization of the regenerate and the number of myelinated axons at this time were similar to those of control chambers, although the endoneurial cross-sectional area was larger in the rAMM chambers. One specimen, however, displayed the very patterns for which the experiments were designed, namely an array of numerous, myelinated axons tracing the spiraling spaces between consecutive lamellae of the rAMM coil.

Amnion↗
PubMed1988

Human amnion membrane matrix as a substratum for axonal regeneration in the central nervous system.

Human Amnion Membrane Matrix (HAMM) was used as a substratum for the regeneration of neuronal axons in the central nervous system. A large piece of HAMM was bound to nitrocellulose paper (NCP) as a supporting material, and cut into small strips. Aspirative lesions of the fimbria-fornix were made in adult rats leaving a cavity separating the septum from the hippocampus. In the same operation a small piece of HAMM-NCP was placed into the cavity with one end abutting the axotomized septum and the other end abutting the denervated hippocampus. At times between 2 weeks and 3 months after surgery the brains of the animals were examined histologically for 1) host response to the implant; 2) maintenance of HAMM-NCP in the originally implanted orientation; 3) growth of acetylcholinesterase (AChE)-positive fibers on the HAMM; 4) growth of the AChE-positive fibers into the denervated hippocampus; and 5) non-neuronal cells on the HAMM. The NCP remained in place over the 3-month period. In most cases the HAMM and NCP remained apposed and caused no greater reaction in the brain beyond that created in response to the aspirative lesion alone. AChE-positive fibers grew out from the septum onto the HAMM by 2 weeks, and by 8 weeks more extensive growth was observed on the HAMM. By 8-weeks, AChE fibers could be clearly seen coming off the membrane and entering the host hippocampus. By double-labelling for the basement membrane side of the HAMM (using anti-human laminin antibodies) and for cholinergic fibers (using AChE histochemistry) in the same sections, it was possible to see fibers clearly growing on the laminin-positive side of the HAMM but little or no growth on the opposing laminin-negative stromal side. The most important variables for extensive growth appeared to be the accurate placement of the implant and the amount of time following the lesions. The placement of the matrix on NCP prior to implantation in the brain made it easier to orient the membrane between the septum and the hippocampus, and seemed to assist in maintaining the membrane in that orientation. The HAMM represents a useful, regeneration-promoting grafting material for central nervous system repair studies.

Acetylcholinesterase↗
PubMed1988

The neurite-promoting domain of human laminin promotes attachment and induces characteristic morphology in non-neuronal cells.

The interaction of cells with laminin and laminin fragments was studied in short-term cell attachment assays. Neurite-promoting chymotrypsin fragments of laminin were isolated using a monoclonal antibody which blocks neurite outgrowth on laminin. The fragments were shown, by electron microscopy after rotary shadowing and by immunological reactivity with different monoclonal antibodies, to contain only the distal end of the long arm. These fragments promoted the attachment and spreading of glioma, sarcoma, carcinoma, muscle, and endodermal cells to the same extent as intact laminin. The attachment was unaffected by peptides containing the RGD sequence. The morphology of the cells on the chymotrypsin fragments was indistinguishable from that on intact laminin but different from the morphology of the same cells on fibronectin. Light microscopy and scanning electron microscopy showed extensive process formation on laminin but not on fibronectin suggestive of increased cell motility in response to laminin. We conclude that the neurite-promoting domain of laminin contains a major site of interaction for non-neuronal cells and that this site induces a cellular response in certain non-neuronal cells that is unique to laminin.

Animals↗