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Biomedical subjects

E C Tsilibary

Publications and source records attributed to E C Tsilibary.

At least 19 recordsLinked to original sources
PubMed1998

Interactions of type IV collagen and its domains with human mesangial cells.

Type IV collagen (COL-IV) interacts with a variety of cell types. We present evidence that human mesangial cells (HMC) bind directly to COL-IV, its major triple helical domain, and the main non-collagenous, NC1 domain. A synthetic peptide, HEP-III, and its triple helical counterpart (THP-III), previously reported to be a heparin-binding domain, also promoted approximately 15% adhesion of HMC. HMC bound to solid-phase-immobilized, intact COL-IV (approximately 75%), isolated NC1 domain (approximately 15%), and a pepsin-derived triple helical fragment,which lacks Hep-III (approximately 65%). We further examined inhibition of HMC adhesion to COL-IV and its domains by using anti-integrin antibodies. Blocking monoclonal antibodies against the alpha2 integrin resulted in 70% inhibition of adhesion to COL-IV and 80% inhibition to HEP-III. Moderate inhibition was observed on the NC1 and triple helical fragments. Anti-alpha1 antibodies inhibited the binding of HMC to COL-IV, the NC1, and triple helical domains, but not to peptide HEP-III. Anti-beta1 antibodies inhibited almost completely (>95%) the adhesion to COL-IV, the NC1, and triple helical fragments; inhibition on HEP-III was approximately 30%. Affinity chromatography studies with solid-phase HEP-III and mesangial cell lysate also demonstrated the presence of integrin alpha2 beta1 along with alpha3 beta1. We conclude that alpha2 beta1 and alpha1 beta1 integrins mediate HMC adhesion to COL-IV. Peptide HEP-III is a major, specific site for alpha2 integrin-mediated binding of mesangial cells to COL-IV. Both the alpha1 beta1 and alpha2 beta1 integrins interact with the NC1 and triple helical fragments of COL-IV. Therefore, we demonstrate that several sites for integrin-mediated interactions exist on several collagenous and non-collagenous domains of COL-IV.

Antibodies, Monoclonal↗
PubMed1997

Alterations in human glomerular epithelial cells interacting with nonenzymatically glycosylated matrix.

The glomerular epithelial cells and the glomerular basement membrane are important constituents of the permselective barrier in the kidney. These are affected in diabetic nephropathy, one of the long-term complications in diabetic patients. Nonenzymatic glycosylation resulting in the accumulation of advanced glycosylation end products correlates with the development of long-term complications in diabetes. The interaction of cells with extracellular matrix proteins plays a critical role in a variety of biological processes. Recent studies show that cell-matrix interactions mediated by integrins can transduce biochemical signals to the cell interior and regulate cell behavior. In this paper we demonstrate that interactions of human glomerular epithelial cells with a nonenzymatically glycated matrix are altered with defective cell spreading, reduced phosphorylation of focal adhesion kinase and reduced activity of mitogen-activated protein kinase. These data suggest that matrix glycation interferes with normal cell-matrix interactions and intracellular signaling that can potentially result in differential gene expression contributing to the changes seen in diabetic nephropathy.

Cell Adhesion↗
PubMed1997

Altered kidney matrix gene expression in early stages of experimental diabetes.

The expression of mRNA and distribution of alpha 1(IV), alpha 3(IV) chains of type IV collagen, matrix metalloproteinase 2 (MMP-2), and tissue inhibitor of metalloproteinase 1 (TIMP-1) were examined in kidneys from streptozotocin-diabetic rats, 2.5 months after administration of the drug, an early time point when specific diabetic glomerular changes were still minimal. Ten age-matched Sprague-Dawley rats were assigned to control and diabetic groups. Compared to the controls, the diabetic rats had a significantly lower body weight, higher kidney weight and serum glucose levels, but no significant changes of glomerular surface area and urine albumin were observed. Northern blot analysis, using whole kidney mRNA, revealed that diabetic rat kidneys expressed 113.5% more alpha 1(IV), 46.5% more alpha 3(IV), 54.8% less MMP-2 and 246% more TIMP-1 (in all instances: p < 0.05). These results were corroborated by in situ hybridization for RNA expression. A quantitative analysis of the data indicated the following changes in glomeruli: (1) 74.6% more alpha 1(IV), (2) 103.8% more alpha 3(IV), (3) 40.7% less MMP-2 and (4) 80.9% more TIMP-1. Similar changes were observed in tubular (proximal and distal) cells. We conclude that an increased synthesis and decreased degradation of renal extracellular matrix components occur early after induction of experimental diabetes, before the onset of typical structural changes in the kidneys, and represent changes of specific gene expression at the transcriptional level. All the cell types in the glomerulus as well as the proximal and distal tubules appear to be involved in this alteration of expression, and this is a novel finding.

Animals↗
PubMed1996

Effect of matrix glycation on expression of type IV collagen, MMP-2, MMP-9 and TIMP-1 by human mesangial cells.

Human mesangial cells grown in either 5 or 25 mM glucose were cultured on type IV collagen which had been previously control-incubated or in vitro glycated. Northern blot analysis revealed that after 3-7 days in culture mesangial cells on glycated type IV collagen expressed approximately 25-200% more alpha 1 (IV), approximately 20-50% less matrix metalloproteinase 2 (MMP-2), and 65-75% more tissue inhibitor of metalloproteinase 1 (TIMP-1). Decreased immunoreactivity (approximately 30-40%) and collagenolytic activity (approximately 10-40%) corresponding to MMP-2 was also detected in media conditioned during the third day of culture on glycated type IV collagen. These effects on cell function were related to the extent of type IV collagen modification and were similar for cells cultured in 5 or 25mM glucose. Elevated glucose (25 vrs 5 mM) increased expression of alpha 1 (IV) mRNA (approximately 40-70%) and in conjunction with matrix glycation resulted in detectable levels of MMP-9 message by northern blot although collagenolytic activity corresponding to MMP-9 was not detectable by zymography. We conclude that glucose and matrix glycation may each alter mesangial cell function, perhaps leading to an imbalance in mesangial matrix synthesis and degradation which could contribute to mesangial expansion characteristic of diabetic renal disease.

Blotting, Northern↗
PubMed1996

Integrin-mediated interactions between primary/T-sv40 immortalized human glomerular epithelial cells and type IV collagen.

The use of human glomerular epithelial cells (HGEC) in research has been severely restricted by several obstacles, which have been circumvented by the generation of T-SV40 immortalized human visceral glomerular epithelial cells (Delarue et al, 1991). In this work, we compared the primary and immortalized HGEC for expression of integrin and some nonintegrin surface receptors. We also studied the adhesion of both types of HGEC to glomerular basement membrane (GBM), type IV collagen (tIV), and its major noncollagenous NC1 domain. The integrins mediating adhesion of HGEC to tIV were also examined. Expression of integrin and some nonintegrin cell surface receptors was analyzed by flow cytometry. Adhesion to GBM, tIV, and its major noncollagenous NC1 domain was studied by direct solid phase cell adhesion assays. Identification of integrins mediating adhesion of HGEC to tIV was achieved by inhibition of cell adhesion using monoclonal antibodies to integrin subunits. The primary and immortalized HGEC share phenotypic characteristics, and alpha3beta1 appeared to be the major integrin present on both HGEC types. The kinetics of binding to GBM, tIV, and its noncollagenous NCI domain were similar in both the primary and immortalized HGEC, although the latter displayed a somewhat weaker binding. Both the primary and immortalized HGEC displayed significantly better adhesion to NC1-alpha3 compared with NC1-alpha1, alpha3beta1 appears to be the major integrin mediating the adhesion of HGEC to tIV. Our studies suggest that alpha3beta1 is the major integrin present on HGEC. This has been confirmed by flow cytometric analysis. In addition, we demonstrated a functional role for this integrin in mediating attachment of HGEC to tIV. Our data also demonstrate a preference in binding of HGEC to alpha3 chains of NC1 compared with alpha1 chains of NC1. These findings were seen in both the primary and immortalized HGEC. The T-SV40 immortalized HGEC can therefore serve as a very useful tool to study glomerular visceral cell biology.

Animals↗
PubMed1995

Putrescine: a novel inhibitor of glycosylation-induced cross-links in laminin.

OBJECTIVE: To determine whether putrescine, a naturally occurring polyamine, is able to prevent nonenzymatic glycosylation-induced cross-linking of basement membrane components. Cross-linking, leading to the formation of advanced glycosylation end products (AGEs) has been proposed as a major mechanism contributing to structural and functional changes of the vascular wall, thus leading to microangiopathy. METHODS: Laminin, a major basement membrane glycoprotein present in the microvasculature, was isolated and incubated in the presence of high glucose concentrations, in order to generate an in vitro diabetic environment. Putrescine was either present or absent from the incubation mixture. Formation of cross-links was assessed by two independent methods: gel electrophoresis and development of characteristic fluorescence. RESULTS: Putrescine inhibited in a dose-dependent manner the formation of slower mobility bands in gel electrophoresis. Quantitation of the development of fluorescence characteristic of glycosylation-induced cross-links demonstrated that putrescine inhibited the formation of fluorescent products. CONCLUSIONS: Putrescine may be a promising compound for inhibition of protein cross-linking and, therefore, could be used in the prevention of diabetic microangiopathy.

Basement Membrane↗
PubMed1995

Glucose-induced alteration of integrin expression and function in cultured human mesangial cells.

Alteration in mesangial volume, due to an increase of the matrix surrounding mesangial cells, is a hallmark indicator of nephropathy in diabetes. Mesangial cells may also play a significant role in the development of nephropathy. Therefore, we examined the effect of glucose on the expression of integrins by cultured human mesangial cells and their ability to interact with collagen IV, a major component of the mesangial matrix. Human mesangial cells were grown in 5 and 25 mM glucose and their integrin profile was examined by immunoprecipitation and flow cytometry in each experimental condition. The results indicate that when mesangial cells were grown in 25 mM glucose, the expression of integrin subunit alpha 2, was increased, while the alpha 1 subunit was considerably decreased, as compared to cells grown in 5 mM glucose. Additionally, mesangial cells were tested for their ability to adhere to collagen IV in a solid-phase assay in the presence of neutralizing antibodies to integrin subunits. The results of these experiments indicate that both alpha 1 and alpha 2 complexed to beta 1 (alpha 2 beta 1 and alpha 1 beta 1) are major mesangial cell receptors for adhesion to collagen IV both in 5 and 25 mM glucose. The two receptors act in concert to mediate adhesion of mesangial cells to type IV collagen. When cell surface expression of the alpha 1 subunit in 25 mM glucose was reduced, the alpha 2 subunit was involved in adhesion to a greater extent than it was in 5 mM glucose. Immunoperoxidase histochemical studies localized both alpha 1 and alpha 2 integrin subunits in the mesangium of normal adult kidneys, suggesting that in vivo interaction with collagen IV could involve both of these receptors. These observations suggest that glucose-induced alterations in integrin expression may modify the ability of mesangial cells to interact with collagen IV.

Antibodies, Monoclonal↗
PubMed1995

Altered proliferation of retinal microvascular cells on glycated matrix.

PURPOSE: To investigate the effect of nonenzymatic glycosylation (glycation) of basement membranes (BM) and isolated BM proteins on the growth of retinal pericytes and retinal endothelial cells. METHODS: Type IV collagen, laminin, Engelbreth-Holm-Swarm tumor basement membrane (EHS-BM) and bovine retinal basement membrane (RBM), after incubation in the presence of reducing sugars to induce glucose-mediated modifications, or in the absence of any sugar (control), were used as a substrate to culture bovine retinal microvascular cells. Cell growth on the nonenzymatically glycosylated and the corresponding control substrates was measured daily, using an automated cell counter. RESULTS: Retinal pericytes seeded on glycated type IV collagen proliferated consistently more slowly than on control type IV collagen (P = 0.02), showing a 20% to 33% decrease throughout most of the growth curve, whereas on glycated laminin the difference from control was not significant. In contrast, proliferation increased by 16% to 25% for retinal endothelial cells on glycated laminin compared with control substrate (P = 0.025), whereas on glycated type IV collagen the growth curve was not significantly different from the curve for the control. When seeded on whole glycated EHS-BM or RBM, proliferation of pericytes decreased by 20% to 30% (P = 0.04); the endothelial cells showed no difference on glycated EHS-BM, however, the growth rate increased on glycated RBM by 25% to 30% more than it did for the control (P = 0.01). CONCLUSIONS: Nonenzymatic glycosylation of intact BM or individual BM macromolecules resulted in reduced proliferation of retinal pericytes and increased proliferation of retinal endothelial cells. These in vitro observations resemble some of the pathologic changes of the retinal microvascular cells observed in situ, when diabetic retinopathy develops.

Animals↗
PubMed1994

Migratory interaction of amphibian epidermal cells with components of the basement membrane.

In adult newts, basal epidermal cells adjacent to a fresh wound move toward the damaged area by migrating over the epidermal basement membrane. In an attempt to determine which basement membrane components mediate this migration, small pieces of glass coated with various natural matrices, purified proteins, or fragments of proteins were implanted into skin wounds such that epidermal cells attempting to form a wound epithelium would encounter the implants. Laminin derived from a cell line (M1536-B3) that produces no type IV collagen was inactive as a migration substrate. Migration on recombinant entactin was somewhat better than on laminin but was still only approximately 14% of that on type I collagen. M15 matrix, a laminin and entactin-containing product of M1536-B3 cells, was no better than entactin alone. Type IV collagen was an excellent substrate, producing slightly more migration than corresponding concentrations of type I collagen at nearly all concentrations tested. Migration on type IV lacking the NC1 domain was at least as good as on intact type IV. All the activity in type IV was present in a 95 kD fragment (alpha 1(IV)95) from the carboxy terminal two-thirds of the alpha 1 chain. Approximately 60% of the activity on alpha 1(IV)95 was obtained on implants coated with a 110 amino acid fragment of the alpha 1 chain derived from the carboxy terminal half of alpha 1(IV)95. Adding the synthetic peptide, arg-gly-asp-ser (RGDS) to the medium, blocked migration on fibronectin-coated implants but had no effect on implants coated with type IV, suggesting that migration on type IV involves different cell surface receptors than those mediating migration over fibronectin. Matrigel, a commercial product containing most basement membrane components, was a poor migration substrate. Thus if type IV mediates basal cell migration toward a wound in vivo, there may have to be some alterations in basement membrane structure to allow epidermal receptors to access type IV active site(s).

Animals↗
PubMed1994

Effects of matrix glycation on mesangial cell adhesion, spreading and proliferation.

We examined the effects of in vitro nonenzymatic glycosylation (NEG) of the extracellular matrix (ECM) on various aspects of the adhesive interaction between the ECM and human kidney mesangial (HKM) cells, and also on the ability of HKM cells to spread and proliferate. Isolated type IV collagen (tIV) or intact complexes of glomerular basement membrane and mesangial matrix (GBM/MM) were used as substrates following control incubation or modest glycation. We observed that HKM cells adhered less effectively to glycated tIV at early time intervals and were delayed in attaining maximal levels of adhesion compared to cells interacting with control tIV. The nature of the adhesive interaction was also different since antibodies which blocked the function of beta 1-containing integrins more effectively inhibited adhesion between HKM cells and glycated tIV than cells and control tIV. HKM cells interacting with glycated tIV also demonstrated less cell surface microspike and ruffle formation at five minutes after plating, less extensive spreading throughout the examined time intervals (> or = 90 min after plating), and slightly increased cell numbers 5 to 10 days after plating when compared to cells interacting with control tIV. However, increased cell numbers were not observed when HKM cells were grown on glycated GBM/MM. Similar changes in response to glycated substrate were observed when HKM cells were grown in either 5 or 25 mM glucose. In conclusion, relatively modest glycation of the ECM alone was sufficient to result in specific changes in HKM cell behavior in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Nonenzymatic glycosylation-induced modifications of intact bovine kidney tubular basement membrane.

We examined structural changes in bovine kidney tubular basement membrane (TBM) following in vitro nonenzymatic glycosylation (NEG). Isolated TBM was incubated for 2 wk at 37 degrees C in the absence of sugar or in the presence of either glucose or ribitol under conditions that minimized degradation and oxidative damage. NEG and crosslink formation in glycated TBM were confirmed by decreased solubility, increased amounts of low mobility material by SDS-PAGE, and increased specific fluorescence compared to controls. Morphological analysis using high resolution, low voltage scanning electron microscopy (LV-SEM) revealed a complex three-dimensional meshwork of interconnecting strands with intervening openings. Glycated TBM underwent distinct morphological changes, including a 58% increase in the amount of image surface area occupied by openings. This was due to an apparent increase in the number of large openings (diameters > 12.5 nm), whereas the number of small openings (diameters < 12.5 nm) remained unchanged. These findings corroborate earlier physiological studies, which established that the loss of glomerular permselectivity seen in patients with diabetic nephropathy is due to the formation of large pores in the kidney filtration barrier of which the BM is a major component. We conclude that NEG and crosslink formation among BM components lead to modifications of BM ultrastructure, which could play a role in loss of barrier function in diabetic microangiopathy and nephropathy.

Animals↗
PubMed1992

Altered cellular interactions between endothelial cells and nonenzymatically glucosylated laminin/type IV collagen.

Laminin and type IV collagen are two major basement membrane glycoproteins. In previous studies it has been shown that nonenzymatic glucosylation induces structural alterations of these macromolecules and also reduces their ability to self-associate. In the present study, endothelial cells were tested for their ability to adhere and spread on nonenzymatically glucosylated laminin and type IV collagen. Adhesion and spreading were reduced when glucosylated macromolecules were used as substrates. Glucosylation-induced changes in adhesion and spreading may be an important initial event signaling other phenotypic modifications of cells in the microvasculature and may be a crucial factor in order to understand the pathogenesis of diabetic microangiopathy at the molecular level.

Animals↗
PubMed1991

A melanoma cell surface laminin binding protein with apparent Mr 90,000.

Laminin promotes adhesion of various cell types via multiple interactions with cell surface components. We have used a laminin domain involved in adhesion of melanoma cells, peptide F9 (Charonis et al., J. Cell Biol. 107:1253 [( 1988]), to examine its specific interaction with cell surface components. Cells were surface labeled, solubilized, and the cell surface associated macromolecules were purified via laminin and F9 affinity columns. We have observed that a macromolecule with apparent molecular weight 90,000 interacts with laminin and peptide F9. This macromolecule does not change electrophoretic mobility upon reduction, cannot be removed from the cell surface by high salt treatment and partitions in the detergent phase of Triton X-114. These results suggest that this macromolecule is associated with melanoma cell surfaces and may be involved in their interaction with laminin.

Animals↗
PubMed1990

Characterization of a synthetic peptide from type IV collagen that promotes melanoma cell adhesion, spreading, and motility.

The adhesion and motility of tumor cells on basement membranes is a central consideration in tumor cell invasion and metastasis. Basement membrane type IV collagen directly promotes the adhesion and migration of various tumor cell types in vitro. Our previous studies demonstrated that tumor cells adhered and spread on surfaces coated with intact type IV collagen or either of the two major enzymatically purified domains of this protein. Only one of these major domains, the pepsin-generated major triple helical fragment, also supported tumor cell motility in vitro, implicating the involvement of the major triple helical region in type IV collagen-mediated tumor cell invasion in vivo. The present studies extend our previous observations using a synthetic peptide approach. A peptide, designated IV-H1, was derived from a continuous collagenous region of the major triple helical domain of the human alpha 1(IV) chain. This peptide, which has the sequence GVKGDKGNPGWPGAP, directly supported the adhesion, spreading, and motility of the highly metastatic K1735 M4 murine melanoma cell line, as well as the adhesion and spreading of other cell types, in a concentration-dependent manner in vitro. Furthermore, excess soluble peptide IV-H1, or polyclonal antibodies directed against peptide IV-H1, inhibited type IV collagen-mediated melanoma cell adhesion, spreading, and motility, but had no effect on these cellular responses to type I collagen. The full complement of cell adhesion, spreading, and motility promoting activities was dependent upon the preservation of the three prolyl residues in the peptide IV-H1 sequence. These studies indicate that peptide IV-H1 represents a cell-specific adhesion, spreading, and motility promoting domain that is active within the type IV collagen molecule.

Amino Acid Sequence↗
PubMed1990

Identification of a multifunctional, cell-binding peptide sequence from the a1(NC1) of type IV collagen.

We have previously identified three distinctive amino acid sequences from type IV collagen which specifically bound to heparin and also inhibited the binding of heparin to intact type IV collagen. One of these chemically synthesized domains, peptide Hep-I, has the sequence TAGSCLRKFSTM and originates from the a1(noncollagenous [NC1]) chain of type IV collagen (Koliakos, G. G., K. K. Koliakos, L. T. Furcht, L. A. Reger, and E. C. Tsilibary. 1989. J. Biol. Chem. 264:2313-2323). We describe in this report that this same peptide also bound to intact type IV collagen in solid-phase assays, in a dose-dependent and specific manner. Interactions between peptide Hep-I and type IV collagen in solution resulted in inhibition of the assembly process of this basement membrane glycoprotein. Therefore, peptide Hep-I should represent a major recognition site in type IV collagen when this protein polymerizes to form a network. In addition, solid phase-immobilized peptide Hep-I was able to promote the adhesion and spreading of bovine aortic endothelial cells. When present in solution, peptide Hep-I competed for the binding of these cells to type IV collagen- and NC1 domain-coated substrata in a dose-dependent manner. Furthermore, radiolabeled peptide Hep-I in solution also bound to endothelial cells in a dose-dependent and specific manner. The binding of radiolabeled Hep-I to endothelial cells could be inhibited by an excess of unlabeled peptide. Finally, in the presence of heparin or chondroitin/dermatan sulfate glycosaminoglycan side chains, the binding of endothelial cells to peptide Hep-I and NC1 domain-coated substrates was also inhibited. We conclude that peptide Hep-I should have a number of functions. The role of this type IV collagen-derived sequence in such diverse phenomena as self-association, heparin binding and cell binding and adhesion makes Hep-I a crucial domain involved in the determination of basement membrane ultrastructure and cellular interactions with type IV collagen-containing matrices.

Amino Acid Sequence↗
PubMed1990

Laminin alterations after in vitro nonenzymatic glycosylation.

Laminin, a basement membrane protein derived from the matrix of the Engelbreth-Holm-Swarm murine tumor, was nonenzymatically glycosylated in vitro in the presence of increasing glucose concentrations. The amount of glucose incorporated per laminin molecule was shown to be proportional to the molarity of glucose used. Nonenzymatic glycosylation resulted in formation of cross-links and alterations of the cruciform shape of laminin molecules; these alterations were dramatic when high concentrations of glucose were used. One of the functions of laminin, the process of self-assembly, was shown to be impaired after in vitro nonenzymatic glycosylation. Glucose incorporation resulted in a dramatic decrease of long-to-long laminin dimers, which normally form during the initial steps of assembly. Furthermore, nonenzymatic glycosylation of laminin reduced its ability to self-associate into complexes larger than dimers, as judged by turbidimetry. The observed decrease of maximal turbidity was proportional to the degree of nonenzymatic glycosylation. Aminoguanidine, which has been suggested to inhibit cross-link formation, was shown to restore to a large extent the shape of laminin, the percentage of long-to-long arm dimers, and the maximal turbidity when included in the mixtures of laminin and glucose. These data suggest that structural and functional alterations of laminin may be primarily due to formation of cross-links. Such modifications of laminin (along with our basement membrane components) may contribute to the morphological and physiological changes observed in basement membranes under diabetic conditions.

Animals↗
PubMed1989

Mapping of three major heparin-binding sites on laminin and identification of a novel heparin-binding site on the B1 chain.

Laminin, a major basement membrane glycoprotein, interacts with many basement membrane- and cell surface-associated heparin-like macromolecules. In order to understand these interactions better, we have tried to map heparin-binding sites on laminin precisely. Electron microscopy revealed three major heparin-binding sites: 1) on the globule of the long arm; 2) on the outer globule of the short arms; and 3) on the inner globule of the short arms. Elution of heparin bound to a laminin affinity column with a linear salt gradient produced three peaks at 0.15, 0.17, and 0.20 M NaCl. When the laminin-heparin interaction was examined in the presence of increasing salt concentrations by the technique of rotary shadowing, the weakest binding was assigned to the inner globule of the short arms and the strongest to the globule of the long arm. One peptide termed AC15, with the sequence Arg-Ile-Gln-Asn-Leu-Leu-Lys-Ile-Thr-Asn-Leu-Arg-Ile-Lys-Phe-Val-Lys from the B1 chain, was identified as a heparin-binding sequence localized on the outer globule of the lateral short arm. Because the two stronger heparin-binding sites were mapped in domains participating in laminin self-association, the effect of heparin on this phenomenon was examined using turbidity and electron microscopy. At low heparin concentrations, laminin oligomer and polymer formation was slightly enhanced. At high heparin concentrations, a drastic inhibition of polymerization was observed, and laminin was detected to be mainly monomeric in rotary-shadowed samples. These results suggest that local variation in the concentration of heparin-like macromolecules might be a crucial factor in determining the association of matrix macromolecules and therefore the structure of basement membranes.

Amino Acid Sequence↗