Type VII collagen is a major structural component of anchoring fibrils.

Abstract

Abstract. Anchoring fibrils are specialized fibrous structures found in the subbasal lamina underlying epithelia of several external tissues. Based upon their sensitivity to collagenase and the similarity in banding pattern to artificially created segment-long spacing crystallites (SLS) of collagens, several authors have suggested that anchoring fibrils are lateral aggregates of collagenous macromolecules. We recently reported the similarity in length and banding pattern of anchoring fibrils to type VII collagen SLS crystallites. We now report the construction and characterization of a murine monoclonal antibody specific for type VII collagen. The epitope identified by this antibody has been mapped to the carboxyl terminus of the major helical domain of this molecule. The presence of type VII collagen as detected by indirect immunofluorescence in a variety of tissues corresponds exactly with ultrastructural observations of anchoring fibrils. Ultrastructural immunolocalization of type VII collagen using a 5-nm colloidal gold-conjugated second antibody demonstrates metal deposition upon anchoring fibrils at both ends of these structures, as predicted by the location of the epitope on type VII collagen. Type VII collagen is synthesized by primary cultures of amniotic epithelial cells. It is also produced by KB cells (an epidermoid carcinoma cell line) and WISH (a transformed amniotic cell line).CHORING fibrils are specialized fibrous structures (5,29) found within the subbasal lamina in human and rat oral mucosa, amphibian skin and notocord, human and rat gingiva, human cervical mucosa, mouse uterus, and human vaginal mucosa, and also along Schwarm cells in unmylelinated nerve fibers in human skin (21). Ultrastructurally, they have a centrosymmetric banding pattern suggesting that they are composed of an aligned lateral aggregate of individual anti-parallel fibrous subunits. The absolute length of these structures is difficult to determine because they undulate in and out of the plane of section, but the longest anchoring fibrils thus far documented approximate 750 nm in length (5). The presumed function of the anchoring fibril is to secure the lamina densa to the underlying connective tissue matrix by physical entrapment of major collagen fibers between the lamina densa and the anchoring fibril. The chemical nature of anchoring fibrils is unknown. Similarity of banding pattern of observed anchoring fibrils with that of artificially aggregated segment-long spacing crystallites (SLS crystallites) ~ of collagens (32) and their sensitivity to destruction by bacterial collagenase (19) suggest that aggregates of collagen may be the major structural component of the anchoring fibril. This concept was further strengthened by the observation that both the dimensions and the 1. Abbreviations used in this paper: ELISA, enzyme-linked immunosorbent assay; SLS crystallites, segment-long spacing crystallites. banding pattern of anchoring fibrils strongly resemble dimeric type VII collagen SLS crystaUites (8). In this report, we ...

The time-dependent rearrangement of the epithelial basement membrane in human skin wounds —immunohistochemical localization of Collagen IV and VII

“…Collagen VII was first called "long chain collagen" and occurs mainly as an antiparallel dimer with overlapping ends [4]. Collagen VII is the major component of the anchoring fibrils in the lamina fibroreticularis of the basement membrane [11,16]. Anchoring fibrils are specialized structures mediating close contact between the lamina densa and the underlying connective tissue.…”

Cellular origin of the dermal‐epidermal basement membrane

“…IF was performed as previously described (Sakai et al, 1986) on 8 pm thick frozen cross-sections of fetal bovine skin, human neonatal foreskin, collagen gel cultures, or on cells cultured on glass slides. Transmission electron microscopy was performed as previously described (Keene et al, 1987).…”

“…More recently, mAb BM165 has been shown to also recognize the 190 kD chain of K-laminin (Marinkovich et al, 1992b). Antikalinin 140 kD chain mAb K140 (Marinkovich et al, 1992a), anti-laminin B1 chain mAb 545 (Marinkovich et al, 1992131, anti-laminin B2 chain mAb 2E8 and anti-laminin A chain mAb 4C7 (Engvall et al, 19861, anti-human type IV collagen mAb 3-8 (Sakai et al, 1982), and anti-type VII collagen mAbs NP32 and NP185 (Sakai et al, 1986) have been previously described. HSPG mAb was demonstrated to recognize HSPG by ELISA and immunoblot analysis (Erwin Schleicher, personal communication) as previously demonstrated for HSPG polyclonal antibody (pAb) Olgemoller et al, 1989).…”

“…Epithelium exposed to external surfaces such as epidermis and cornea are associated with an especially complex form of basement membrane which contains specialized ultrastructural entities with unique biochemical components (Montagna, 1992). These include hemidesmosomes which contain bullous pemphigoid antigens (Li et al, 1991;Stanley, 19911, anchoring filaments which contain kalinin (Rousselle et al, 1991) and K-laminin (Marinkovich et al, 1992b), and anchoring fibrils which contain type VII collagen (Sakai et al, 1986).…”

The bone morphogenetic protein 1/Tolloid-like metalloproteinases

“…Anchoring fibrils, consisting of type VII collagen, are important structural components that mediate attachment of epidermis to underlying stroma (Sakai et al, 1986). Synthesized and secreted by epidermal keratinocytes, type VII procollagen monomers self-assemble into antiparallel dimers, which then associate laterally to form anchoring fibrils Morris et al, 1986).…”