This is the extracellular link domain of the type found in human TSG-6. The link domain is a hyaluronan (HA)-binding domain. TSG-6 is the protein product of tumor necrosis factor-stimulated gene-6. TSG-6 is up-regulated in inflammatory lesions and in the ovary during ovulation. It has a strong anti-inflammatory and chondroprotective effect in models of acute inflammation and autoimmune arthritis and plays an essential role in female fertility. Also included in this group are the stabilins: stabilin-1 (FEEL-1, CLEVER-1) and stabilin-2 (FEEL-2). Stabilin-2 functions as the major liver and lymph node-scavenging receptor for HA and related glycosaminoglycans. Stabilin-2 is a scavenger receptor with a broad range of ligands including advanced glycation end (AGE) products, acetylated low density lipoprotein and procollagen peptides. In contrast, stabilin-1 does not bind HA, but binds acetylated low density lipoprotein and AGEs with lower affinity. As AGEs accumulate in vascular tissues during aging and diabetes, these receptors may be implicated in the pathologies of these states. Both stabilins are present in the early endocytic pathway in hepatic sinusoidal epithelium associating with clathrin/AP-2. Stabilin-1 is expressed in macrophages. Stabilin-2 is absent from the latter. In macrophages: stabilin-1 is involved in trafficking between early/sorting endosomes and the trans-Golgi network. Stabilin-1 has also been implicated in angiogenesis and possibly leucocyte trafficking. Both stabilins bind gram-positive and gram-negative bacteria. TSG-6 and stabilins contain a single link module which supports high affinity binding to HA.
Jiyao W et al.(2023). "The conserved domain database in 2023.",