A brain extracellular matrix proteoglycan forms aggregates with hyaluronan.
Unlike many tissues, the adult central nervous system extracellular matrix (ECM) has few known components. Previously, we characterized a large chondroitin sulfate proteoglycan, pgT1, from adult rat brain which has the properties of a general brain ECM component and is immunologically distinct from aggrecan and versican (Iwata, M., and Carlson, S.S. (1993) J. Neurosci. 13, 195-207). In this study we demonstrate that pgT1 binds hyaluronan with relatively high affinity. The pgT1 preparation isolated from rat brain aggregates in non-denaturing conditions. This aggregation is abolished by incubation of pgT1 with Streptomyces hyaluronidase. Examination of these aggregates by electron microscope reveals a structure in which an average of 18 subunits arise laterally from opposite sides of an elongated 350-nm filament. These pgT1 aggregates resemble the proteoglycan aggregates in cartilage which are composed of aggrecan and hyaluronan. Using affinity coelectrophoresis, we measure a dissociation constant (Kd) of 0.9 +/- 0.2 nM for the interaction of pgT1 and hyaluronan. These new findings, combined with the general distribution of pgT1 in brain, suggest that pgT1/hyaluronan aggregates are an extended general structure of the brain extracellular matrix network.
Iwata
M
M
Department of Physiology and Biophysics, University of Washington, Seattle 98195.
Wight
T N
TN
Carlson
S S
SS
D000818:Animals; D001665:Binding Sites; D001921:Brain / Q000378:metabolism*; D002850:Chromatography, Gel; D004586:Electrophoresis / Q000379:methods; D005109:Extracellular Matrix / Q000378:metabolism*; D000882:Haplorhini; D006820:Hyaluronic Acid / Q000378:metabolism*; D006821:Hyaluronoglucosaminidase / Q000378:metabolism; D008854:Microscopy, Electron; D011509:Proteoglycans / Q000302:isolation & purification / Q000378:metabolism* / Q000648:ultrastructure; D051381:Rats; D017207:Rats, Sprague-Dawley
D011509:Proteoglycans; D006820:Hyaluronic Acid; D006821:Hyaluronoglucosaminidase