Two Sets of Interacting Collagens Form Functionally Distinct Substructures within a Caenorhabditis elegans Extracellular Matrix

A ubiquitous feature of collagens is protein interaction, the trimerization of monomers to form a triple helix followed by higher order interactions during the formation of the mature extracellular matrix. The Caenorhabditis elegans cuticle is a complex extracellular matrix consisting predominantly of cuticle collagens, which are encoded by a family of ∼154 genes. We identify two discrete interacting sets of collagens and show that they form functionally distinct matrix substructures. We show that mutation in or RNA-mediated interference of a gene encoding a collagen belonging to one interacting set affects the assembly of other members of that set, but not those belonging to the other set. During cuticle synthesis, the collagen genes are expressed in a distinct temporal series, which we hypothesize exists to facilitate partner finding and the formation of appropriate interactions between encoded collagens. Consistent with this hypothesis, we find for the two identified interacting sets that the individual members of each set are temporally coexpressed, whereas the two sets are expressed ∼2 h apart during matrix synthesis

The autoantigen in anti-p200 pemphigoid is synthesized by keratinocytes and fibroblasts and is distinct from nidogen-2

Anti-p200 pemphigoid is a subepidermal immunobullous disorder associated with tissue-bound and circulating autoantibodies reactive with a 200 kDa protein on the dermal side of salt-split-skin. The autoantigen, named p200, is a non-collagenous glycoprotein located at the lamina lucida-lamina densa border of the epidermal basement membrane. However, its identity and cellular origin remain elusive. Here, we used biochemical and genetic approaches to characterize the autoantibody reactivity in three new patients with anti-p200 pemphigoid. We show that the target antigen p200 is synthesized by both keratinocytes and fibroblasts, is disulfide-bonded, and participates in calcium-dependent molecular interactions. Lack of collagen XVII (BP 180), collagen VII, or laminin 332 (laminin 5) from the dermal-epidermal junction does not destabilize p200. Colocalization within the basement membrane zone and an identical molecular weight suggested nidogen-2 as candidate autoantigen in anti-p200 pemphigoid, but biochemical analysis demonstrated that p200 is distinct from nidogen-2. In conclusion, the results define further the biochemical characteristics of p200 and demonstrate its in vitro-synthesis by keratinocytes and fibroblasts, thus providing a basis for identification and further characterization of this autoantigen