Abstract

Collagen XIII belongs to the subgroup of collagenous transmembrane proteins. It has a wide tissue distribution and has been localized to many sites of cell-matrix and cell-cell interaction in tissues.

Biochemical and in silico analyses of collagen XIII and other collagenous transmembrane proteins revealed that the biosynthesis of this structurally varied group is characterized by a coiled-coil motif following the transmembrane domain, and these trimerization domains appear to be associated with each of the collagenous domains. The collagen XIII trimer was shown to have an interchain disulfide bond at the junction of the NC1 and COL1 domains, and several other collagenous transmembrane proteins have a pair of cysteines in the same location. Furthermore, furin cleavage at the NC1 domain can be expected in most of the proteins.

Mice heterozygous for the Col13a1^del transgene, encoding a mutant collagen XIII, developed clonal mature B-cell lineage lymphomas originating in the mesenteric lymph node (MLN). The incidence of disease in conventionally reared mice was 2-fold higher than for mice raised in a specific pathogen-free facility. The lymphomas often associated with large populations of macrophages and T cells. Lymphomas expressed little if any collagen XIII, suggesting that the effect of the mutation was B-cell extrinsic and likely to be associated with collagen XIII-positive tissues drained by the MLN. Studies of the small intestines of transgenic mice showed highly abnormal subepithelial basement membranes (BM), associated with heightened expression of genes involved in immune responses. These findings suggest that collagen XIII-dependent maintenance of the intestinal BM is a critical determinant of cancer susceptibility.

Collagen XIII exhibited a wide tissue distribution at the protein level, and the most intense expression was found in lung. Tissues contained 1-4 collagen XIII polypeptides, their size ranging between 78 and 102 kDa. Collagen XIII staining was detected in a restricted set of blood vessels in the liver, pancreas, adrenal gland, epididymis and brain. Moreover, Col13a1^del transgene expression in the absence of endogenous collagen XIII proved to be deleterious for mouse embryonal development, leading to early fetal mortality.