Structural basis for apparent heterogeneity of collagens in human basement membranes: type IV procollagen contains two distinct chains.

Abstract

Fetal cells isolated from human amniotic fluid synthesize type IV procollagen when grown in monolayer culture. The procollagen, which contains two biochemically distinct chains, was found to be structurally and immunologically related to type IV collagen chains and collagenous fragments isolated from human placenta. Limited pepsin digestion of the intact procollagen that was deposited in the cell layer during culture produced a heterogeneous population of collagenous peptides comparable to that obtained during isolation of type IV collagens from human tissues. These studies support the hypothesis that basement membranes contain at least two genetically distinct type IV procollagen chains and suggest that the heterogeneity of collagenous components obtained after pepsin digestion of tissues and isolated basement membranes can result from degradative cleavage of the procollagen at a limited number of protease-sensitive sites.Collagen a chains have been isolated from pepsin digests of basement membranes obtained from several tissues, including renal glomerulus and lens capsule, and on the basis of these studies it has been proposed that basement membranes contain a distinct collagen or procollagen composed of three identical chains (1, 2). However, other investigators using renal glomerular basement membranes have described a more h-eterogeneous mixture of collagenous peptides. that are both larger and smaller than a chains from interstitial collagens (types I-III) (3-6). Comparable heterogeneity has been described for type IV collagen isolated from human placenta, and evidence has recently been obtained which suggests that the collagen fragments could be derived from two, genetically distinct, type IV collagen chains (7-10).Epithelioid amniotic fluid cells synthesize a variety of connective tissue macromolecules in culture, including fibronectin (I1), type I and type I trimer procollagens (12), and a type IV procollagen (13). The last protein, which has been purified from culture medium by salt fractionation and ion-exchange chromatography, resembles collagenous proteins extracted from basement membranes in amino acid composition and degree of posttranslational hydroxylation and glycosylation. Although the unreduced procollagen migrated on NaDodSO4/polyacrylamide gel electrophoresis as a single band above type I procollagen, after reduction two closely spaced chains were observed that migrated between collagen 3 components and proal(I) chains. In this paper we present evidence that procollagen from amniotic fluid cells is immunologically and structurally related to type IV collagen fragments isolated from human placenta, and that the heterogeneity of collagenous components obtained after pepsin digestion of tissues is secondary to degradative cleavage of two genetically distinct type IV Isolation of Procollagen and Collagen. Medium procollagen was isolated by salt precipitation and ion-exchange chromatography on DEAE-and carboxymethyl-cellulose (12, 13). To isolate collagenous proteins from the matrix, ...

Cultured human amniotic fluid cells characterized with antibodies against intermediate filaments in indirect immunofluorescence microscopy.

“…Results with histidase assays on AF cell cultures demonstrated two types of cells, the epithelial cells being histidase positive while no enzyme was found in fibroblasts (4,33). Priest and his collaborators (7-9) and Crouch et al (10)(11)(12)(13) were able to distinguish fibroblasts among amniotic fluid cell cultures based on the production of type I and type III collagen and fibronectin (8,10,11), similarly to the cultured human fibroblast cell lines (34). Epithelial cell clones in AF cell cultures, on the other hand, secreted type IV collagen (7,8,(11)(12)(13), found in various basement membranes (cf.…”

“…Attempts have also been made to characterize cultured AF cells on the basis of their production of extracellular matrix proteins, detectable both in the culture fluid and in the cell layers (7)(8)(9)(10)(11)(12)(13) (Fig. 1, lanes 1, 2; 17, 18).…”

Associations of Matrix Metalloproteinase-9 Protein Polymorphisms with Lymph Node Metastasis but not Invasion of Gastric Cancer

“…Together with MMP-2, MMP-9 is a gelatinase and belongs to a subfamily of MMP family. It can degrade denatured collagens (gelatins) and type IV collagen, which is the major structural component of the extracellular matrix (4,5). Higher expression of MMP-9 is involved in the progression of many cancers, including gastric cancer (6 -9).…”

The role of the main noncollagenous domain (NC1) in type IV collagen self-assembly.

“…T YPE IV collagen is one of the exclusive macromolecular components of basement membranes (11). Structurally, it consists of three a-chains [tIl(IV)2-t12(IV)] and has in its monomeric form a molecular weight of 500,000 (1,5). When compared to the a-chains of the other collagen types, the a-chains of type IV collagen are of higher molecular weight and contain along their length many short interruptions of the GIy-X-Y repeating unit (9,18).…”