Laminin assembles into separate basement membrane and fibrillar matrices in Schwann cells

Laminins are important for Schwann cell basement membrane assembly and axonal function. In this study, we found that exogenous laminin-1, like neuromuscular laminins-2/4, formed two distinct extracellular matrices on Schwann cell surfaces, each facilitated by laminin polymerization. Assembly of one, a densely-distributed reticular matrix, was accompanied by a redistribution of cell-surface dystroglycan and cytoskeletal utrophin into matrix-receptor-cytoskeletal complexes. The other, a fibrillar matrix,accumulated in separate zones associated with pre-existing β1-integrin arrays. The laminin-1 fragment E3 (LG-modules 4-5), which binds dystroglycan and heparin, inhibited reticular-matrix formation. By contrast,β1-integrin blocking antibody (Ha2/5) prevented fibrillar assembly. Ultrastructural analysis revealed that laminin treatment induced the formation of a linear electron-dense extracellular matrix (lamina densa)separated from plasma membrane by a narrow lucent zone (lamina lucida). This structure was considerably reduced with non-polymerizing laminin, fully blocked by E3, and unaffected by Ha2/5. Although it formed in the absence of type IV collagen, it was nonetheless able to incorporate this collagen. Finally, cell competency to bind laminin and form a basement membrane was passage-dependent. We postulate that laminin induces the assembly of a basement membrane on competent cell surfaces probably mediated by anchorage through LG 4-5. Upon binding, laminin interacts with dystroglycan,mobilizes utrophin, and assembles a `nascent' basement membrane, independent of integrin, that is completed by incorporation of type IV collagen. However,the fibrillar β1-integrin dependent matrix is unlikely to be precursor to basement membrane.

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Assembly of the exogenous extracellular matrix during basement membrane formation by alveolar epithelial cells in vitro

Journal of Cell Science ◽

10.1242/jcs.113.5.859 ◽

2000 ◽

Vol 113 (5) ◽

pp. 859-868 ◽

Cited By ~ 1

Author(s):

A. Furuyama ◽

K. Mochitate

Keyword(s):

Epithelial Cells ◽

Basement Membrane ◽

Type Iv Collagen ◽

Alveolar Epithelial Cells ◽

Coarse Mesh ◽

Lamina Densa ◽

Alveolar Epithelial ◽

Type Iv ◽

Laminin 1

We found that immortalized alveolar type II epithelial cells (SV40-T2 cells) that were cultured on dense fibrillar collagen supplemented with Matrigel gel formed a thin and continuous lamina densa beneath them. Immunohistochemical analysis of laminin-1, type IV collagen, entactin (nidogen) and perlecan in the culture indicated that all these components were integrated into a sheet structure of basement membrane beneath the cells. Analysis of the temporal and spatial distribution of the basement membrane macromolecules revealed that the initial deposits of laminin-1 and entactin were significantly greater in area in the presence of Matrigel. These globular deposits and the coarse mesh of basement membrane macromolecules developed into a flat membranous basement membrane. In the absence of Matrigel, the SV40-T2 cells failed to form a continuous lamina densa, and the deposits stayed in the coarse mesh. The major biotinylated Matrigel components that were integrated into the basement membrane were laminin-1 and entactin. Furthermore, SV40-T2 cells supplemented with exogenous laminin-1 alone as well as laminin-1 contaminated with entactin formed a continuous lamina densa. These results indicate that the laminin-1 and entactin supplied from the Matrigel were incorporated into a basement membrane beneath the SV40-T2 cells, and contributed to the formation of basement membrane. Therefore, we concluded that the alveolar epithelial cells synthesize laminin-1, entactin, type IV collagen, and perlecan, but that they also needed to assemble exogenous laminin-1 into the basement membrane to complete its formation in vitro.

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Possible continuity of subplasmalemmal cytoplasmic network with basement membrane cord network: ultrastructural study

Journal of Cell Science ◽

10.1242/jcs.108.5.1971 ◽

1995 ◽

Vol 108 (5) ◽

pp. 1971-1976

Author(s):

S. Inoue

Keyword(s):

Basement Membrane ◽

Type Iv Collagen ◽

Freeze Substitution ◽

High Resolution Electron Microscopy ◽

Sulfate Proteoglycan ◽

Glutaraldehyde Fixation ◽

Lamina Densa ◽

Type Iv ◽

Resolution Electron ◽

Visceral Epithelium

The ultrastructure of the subplasmalemmal cytoplasm of the cell and the associated basement membrane as well as the area of the cell-basement membrane border were observed with high resolution electron microscopy after preparation of the tissues with cryofixation or glutaraldehyde fixation followed by freeze substitution. The subplasmalemmal cytoplasm of the smooth muscle cells of rat epididymal tubules and the podocyte processes of the mouse glomerular visceral epithelium were found to be composed of a fine network of irregular anastomosing strands. This network closely resembled the previously characterized cord network of the basement membrane. The cords are known to be composed of a 1.5 to 3 nm thick core filament made up of type IV collagen which is surrounded by an irregular ‘sheath’ of other components. The strands in the subplasmalemmal network showed ultrastructural features similar to those of the cord network. Ribbon-like, 4.5 nm wide heparan sulfate proteoglycan ‘double tracks’ were previously reported to be associated with the cord network. Structures similar in size and appearance to the double tracks were also found in the subplasmalemmal network. At the cell-basement membrane border, the lamina densa of the basement membrane was in contact with the cell without the intervening space of a lamina lucida which was recently found to be an artefact caused by conventional tissue processing. Furthermore, the subplasmalemmal network appeared to be continuous through the plasma membrane, with the cord network of the basement membrane.(ABSTRACT TRUNCATED AT 250 WORDS)

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A Post-Embedding Colloidal Gold Immunocytochemical Approach To The Study Of Matrix Accumulation In Glomerular Basement Membrane.

Microscopy and Microanalysis ◽

10.1017/s1431927600020006 ◽

1999 ◽

Vol 5 (S2) ◽

pp. 1336-1337

Author(s):

Caroline A. Miller ◽

Dominic Cosgrove

Keyword(s):

Basement Membrane ◽

Glomerular Basement Membrane ◽

Type Iv Collagen ◽

Immunohistochemical Analysis ◽

Ultrastructural Localization ◽

Type Iv ◽

Progressive Loss ◽

Matrix Accumulation ◽

Immunocytochemical Approach ◽

Laminin 1

Alport renal disease pathogenesis is characterized by a progressive irregular thickening, thinning, and splitting of the glomerular basement membrane (GBM), which culminates in a focal and segmental glomerulonephritis and progressive loss of glomerular filtration, leading to uremia and death. A mouse model for this disease was produced using a gene targeting approach (Cosgrove et al., 1996). The resulting model displays renal pathology that is very similar to that observed in humans. As matrix accumulation has long been associated with the thickened regions of the GBM, this model provided a means to study the molecular composition and ultrastructural localization of matrix in these rarefied regions of the GBM in the Alport mouse.We examined three matrix molecules based on preliminary data; type IV collagen α l and α2 chains, laminin-1 and fibronectin. Immunohistochemical analysis showed that while all three of these molecules localize primarily to the mesangial matrix of normal mouse glomeruli, in the Alport glomeruli these molecules seem to be heavily deposited in the GBM.

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Structure, compositon and function of the dermal-epidermal junction: Relevance in cutaneous disease and diagnosis

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100156328 ◽

1989 ◽

Vol 47 ◽

pp. 868-869

Author(s):

K. A. Holbrook

Keyword(s):

Basement Membrane ◽

Epidermolysis Bullosa ◽

Normal Skin ◽

Lamina Densa ◽

Inherited Disorders ◽

Ultrastructural Studies ◽

Type Iv ◽

Type Vii Collagen ◽

Attachment Structures ◽

Matrix Components

The dermal-epidermal junction (DEJ), or basement membrane rone, is the boundary between the epithelial and mesenchymal compartments of the skin; epidermal and fibroblastic cells in these two regions collaborate to synthesire its components. Ultrastructural studies (TEM and SEM) have defined a series of planes or layers (basal epidermal, lamina lucida, lamina densa, sublamina densa) and the morphology and density of attachment structures (hemidesmosomes, anchoring filaments, anchoring fibrils and anchoring plaques) in this region of normal skin. Change in structure of the DEJ provides information about the history of the tissue; reduplication of the lamina densa, for example, indicates a site of cell detachment or migration, or remodelling that accompanies repair of focal damage. In normal skin the structure of the DEJ is stable; in pathologic conditions it can be compromised by the congenital absence of certain structures or antigens (e.g., in the inherited disorders, epidermolysis bullosa [EB]) or by enzymatic degradation (e.g., in tumor invasion). Dissolution of the DEJ can also occur normally during the formation of epidermal appendages (e.g., hair follicles) and as melanocytes and Langerhans cells migrate into the epidermis during development.Biochemical and immunohisto/cytochemical studies have identified more than 20 molecules at the DEJ. These include well known matrix molecules (e.g., types IV and V collagen, laminin and fibronectin) and skin-specific antigens. The latter have been identified by autoantibodies or specific polyclonal or monoclonal antibodies raised against the skin, cultured cells and other epithelia. Some of the molecules of the DEJ are are present in basement membrane zones of many epithelia and thus are considered ubiquitous components (type IV, V, laminin, fibronectin, nidogen, entactin, HSPG, LDA-1, CSP [3B3]). All of them (that have been investigated in developing skin) appear ontogenetically as early as human embryonic tissue can be obtained and their expression is typically normal in patients with EB. The known properties of many of these molecules (particularly the matrix components) suggest functions they might impart to the DEJ: support of an epithelium (type IV collagen), regulation of permeability (heparan sulfate proteoglycan) or facilitation of cell attachment (fibronectin) and movement (laminin). Another group of matrix components and antigens of the DEJ includes molecules that are skin-specific or characteristic of stratified squamous epithelia (type VII collagen=LH 7:2 antigen, bullous pemphigoid antigen, AA3, GB3, KF-1,19-DEJ-1, epidermolysis bullosa acquisita antigen [EBA], AF-1 and AF-2, cicatricial pemphigoid antigen [CPA]) . These molecules are expressed in the DEJ later in development than the first group of molecules, in conjunction with the morphologic appearance of the structure they represent. Their appearance is also coordinated with specific developmental events (e.g., epidermal stratification) and the expression of molecules of differentiation in the epidermis and dermis. One or more of them is typically absent or reduced in expression in the skin of patients with heritable disorders affecting this region. There is no apparent correlation between the location of molecules in the DEJ and the stability of their expression.

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Dynamically remodeled hepatic extracellular matrix predicts prognosis of early-stage cirrhosis

Cell Death and Disease ◽

10.1038/s41419-021-03443-y ◽

2021 ◽

Vol 12 (2) ◽

Author(s):

Yuexin Wu ◽

Yuyan Cao ◽

Keren Xu ◽

Yue Zhu ◽

Yuemei Qiao ◽

...

Keyword(s):

Liver Cirrhosis ◽

Basement Membrane ◽

Type Iv Collagen ◽

Patient Survival ◽

Early Stage ◽

Ecm Remodeling ◽

Type Iv ◽

Ecm Proteins ◽

Stage Disease ◽

Cirrhotic Patients

AbstractLiver cirrhosis remains major health problem. Despite the progress in diagnosis of asymptomatic early-stage cirrhosis, prognostic biomarkers are needed to identify cirrhotic patients at high risk developing advanced stage disease. Liver cirrhosis is the result of deregulated wound healing and is featured by aberrant extracellular matrix (ECM) remodeling. However, it is not comprehensively understood how ECM is dynamically remodeled in the progressive development of liver cirrhosis. It is yet unknown whether ECM signature is of predictive value in determining prognosis of early-stage liver cirrhosis. In this study, we systematically analyzed proteomics of decellularized hepatic matrix and identified four unique clusters of ECM proteins at tissue damage/inflammation, transitional ECM remodeling or fibrogenesis stage in carbon tetrachloride-induced liver fibrosis. In particular, basement membrane (BM) was heavily deposited at the fibrogenesis stage. BM component minor type IV collagen α5 chain expression was increased in activated hepatic stellate cells. Knockout of minor type IV collagen α5 chain ameliorated liver fibrosis by hampering hepatic stellate cell activation and promoting hepatocyte proliferation. ECM signatures were differentially enriched in the biopsies of good and poor prognosis early-stage liver cirrhosis patients. Clusters of ECM proteins responsible for homeostatic remodeling and tissue fibrogenesis, as well as basement membrane signature were significantly associated with disease progression and patient survival. In particular, a 14-gene signature consisting of basement membrane proteins is potent in predicting disease progression and patient survival. Thus, the ECM signatures are potential prognostic biomarkers to identify cirrhotic patients at high risk developing advanced stage disease.

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