Expression of Type XXIII Collagen mRNA and Protein

Abstract

Collagen XXIII is a member of the transmembranous subfamily of collagens containing a cytoplasmic domain, a membrane-spanning hydrophobic domain, and three extracellular triple helical collagenous domains interspersed with non-collagenous domains. We cloned mouse, chicken, and human ␣1(XXIII) collagen cDNAs and showed that this non-abundant collagen has a limited tissue distribution in non-tumor tissues. Lung, cornea, brain, skin, tendon, and kidney are the major sites of expression. In contrast, five transformed cell lines were tested for collagen XXIII expression, and all expressed the mRNA. In vivo the ␣1(XXIII) mRNA is found in mature and developing organs, the latter demonstrated using stages of embryonic chick cornea and mouse embryos. Polyclonal antibodies were generated in guinea pig and rabbit and showed that collagen XXIII has a transmembranous form and a shed form. Comparison of collagen XXIII with its closest relatives in the transmembranous subfamily of collagens, types XIII and XXV, which have the same number of triple helical and non-collagenous regions, showed that there is a discontinuity in the alignment of domains but that striking similarities remain despite this.Tissues use specific sets of collagens, often synthesized simultaneously, to achieve and maintain particular functional properties. Most collagens are secreted and assembled within the extracellular environment; however, a growing subclass of collagens are transmembranous and inserted into the plasma membrane in a type II orientation to extend their extracellular collagenous domains from the cell surface.The subclass of transmembranous collagens currently includes types XIII, XVII, XXIII, and XXV, summarized in a recent review (1). The group has also been referred to as the MACITs for membrane-associated collagens with interrupted triple helices (2). Type XIII collagen, the first member of the group identified (3), has an important function in muscle tissue. Engineered genetic mutations in the Col13a1 gene in one case causes cardiovascular defects (4) and in another causes abnormal skeletal muscle myofibers with progressive myopathy that is worsened by exercise (5). Type XIII collagen mediates cell attachment through integrin ␣1␤1 but does not interact through another common collagen receptor, ␣2␤1 (6). The second transmembranous collagen to be identified was type XVII (7), which was known for many years as bullous pemphigoid antigen 2 and BP180 prior to the elucidation of its collagenous nature. Being a component of the hemidesmosome (8), type XVII collagen provides structural integrity to the cornea (9 -11) and skin (12), clearly demonstrated by mutations in the COL17A1 gene that cause epidermolysis bullosa (13, 14). Our laboratories added collagen XXIII to the family of transmembranous collagens by identifying a human EST 3 and using its sequence to clone a fragment of chicken collagen XXIII cDNA to examine its expression in cornea (15). We also cloned the full-length mouse collagen XXIII cDNA sequence and deposited it into GenBan...

Collagen XXIII, Novel Ligand for Integrin α2β1 in the Epidermis

“…A. E.), and SFB829 (to M. K., T. K., and B. E. integrin ␣I-domains 2 (29), and integrin ␣ 2 ␤ 1 ectodomain (30) were done as described previously. The polyclonal anti-collagen XXIII antibody was described previously (4). Rat monoclonal antibody against integrin ␣ 2 was purchased from Emfret, and mouse monoclonal antibody against E-cadherin was purchased from BD Transduction Laboratories.…”

“…Keratinocyte Plasma Membrane-We recently described the expression pattern of collagen XXIII in mouse embryos and showed that it is present in a variety of different epithelia (4). To extend these observations, we compared expression of collagen XXIII with that of integrin ␣ 2 ␤ 1 in the epidermis and in tongue epithelium of embryonic (E18.5) and adult (P60) mice (Fig.…”

“…The sequence of mouse collagen XXIII does not contain this motif, but two similar motives containing GER triplets, 434 GTSGER 439 and 488 GEKGER 493 , are present. The latter is conserved in collagen XXIII of all species so far sequenced (4). To analyze whether those motives function as integrin ␣ 2 ␤ 1 binding sites, we inserted them into model fusion proteins containing a bacteriophage foldon and flanking GPP 5 linkers (43).…”

“…The proteolytic processing releasing the ectodomain is mediated by furin and is regulated by the plasma membrane microenvironment (5). Collagen XXIII is expressed in the epidermis and other epithelia such as those in the tongue, gut, and lung but also in the brain and kidney (4). In prostate, collagen XXIII expression was shown to correlate with tumor progression (6).…”

“…Collagen XXIII forms homotrimers consisting of a short intracellular domain, a single-pass transmembrane domain and three extracellular collagen domains interrupted by short noncollagenous sequences (3,4). It exists either as a full-length, membrane-anchored protein or as a soluble ectodomain.…”