Biglycan

Biglycan is a small is_associated_with::leucine-rich repeat is_associated_with::proteoglycan (SLRP) which is found in a variety of extracellular matrix tissues, including is_associated_with::bone, is_associated_with::cartilage and is_associated_with::tendon. In humans, biglycan is encoded by the BGN is_associated_with::gene which is located on the is_associated_with::X chromosome.

The name "biglycan" was proposed in an article by Fisher, Termine and Young in an article in the is_associated_with::Journal of Biological Chemistry in 1989 because the is_associated_with::proteoglycan contained two GAG chains; formerly it was known as proteoglycan-I (PG-I).

Structure
Biglycan consists of a protein core containing leucine-rich repeat regions and two glycosaminoglycan (GAG) chains consisting of either is_associated_with::chondroitin sulfate (CS) or is_associated_with::dermatan sulfate (DS), with DS being more abundant in most is_associated_with::connective tissues. The CS/DS chains are attached at amino acids 5 and 10 in human biglycan. The composition of the GAG chains has been reported as varying according to tissue of origin. Non-glycanated forms of biglycan (no GAG chains) increase with age in human articular is_associated_with::cartilage.

The composition of GAG chains of biglycan and is_associated_with::decorin originating from the same tissue has been reported to be similar.

The structure of biglycan core protein is highly conserved across species; over 90% homology has been reported for rat, mouse, bovine and human biglycan core proteins.

Function
Biglycan is believed to play a role in the mineralization of bone. is_associated_with::Knock-out mice that have had the gene for biglycan suppressed (Bgn -/-) have an is_associated_with::osteoporosis-like is_associated_with::phenotype with reduced growth rate and lower is_associated_with::bone mass than mice that can express biglycan.

Biglycan core protein binds to the is_associated_with::growth factors is_associated_with::BMP-4 and influences its bioactivity. It has also been reported that the presence of biglycan is necessary for is_associated_with::BMP-4 to exert its effects on is_associated_with::osteoblasts. There is also evidence that biglycan binds to is_associated_with::TGF-beta 1.

Interactions
Biglycan interacts with is_associated_with::collagen, both via the core protein and GAG chains. It has been reported that biglycan interacts more strongly with is_associated_with::collagen type II than is_associated_with::collagen type I. Biglycan has been reported to compete with is_associated_with::decorin for the same binding site on is_associated_with::collagen.

Biglycan has been shown to interact with is_associated_with::SGCA.