Association of laminin with heparan and chondroitin sulfate-bearing proteoglycans in neurite-promoting factor complexes from rat schwannoma cells.
The present studies were undertaken to confirm the presence and identity of a putative proteoglycan associated with laminin in neurite-promoting factor complexes isolated from rat schwannoma cell conditioned medium. Sucrose density gradient centrifugation of the complex resolved two laminin-associated Na2[35S]O4-labeled peaks which were termed Pools A and B. Both pools had nearly all their [35S] cpms associated with glycosaminoglycan, contained heparan sulfate-proteoglycan core protein antigen and displayed a similarly high neurite promoting potency relative to their laminin contents. However, Pool A contained about twice as many [35S] cpms and twice as much proteoglycan core protein per laminin than Pool B. Seventy percent of Pool A cpms was associated with heparan sulfate and 30% with chondroitin sulfate whereas the inverse was true for Pool B. Treatment with heparitinase and/or chondroitinase ABC caused laminin in either pool to elute at lower salt concentrations from DEAE cellulose. In SDS-PAGE the [35S] cpms of both pools ran with the same mobility as laminin but could be separated from laminin under reducing conditions. The Pool A cpms remained at 900 KD and the Pool B cpms spread over the 200-900 KD range. By rotary shadowing electron microscopy, Pool B fractions contained primarily cross-shaped laminin images, often associated with proteoglycan-like images. Pool A fractions contained i) dense, aggregated images including intact laminin from which emanated proteoglycan-like strands, ii) circular images bearing globular domains and less commonly, iii) distorted cross-shaped laminin-like images. These studies support the existence of at least two forms of laminin-proteoglycan complexes which differ in biochemical, immunochemical and ultrastructural characteristics.
D000818:Animals; D002478:Cells, Cultured; D002807:Chondroitin / Q000031:analogs & derivatives*; D002809:Chondroitin Sulfates / Q000032:analysis*; D006025:Glycosaminoglycans / Q000032:analysis*; D006497:Heparan Sulfate / Q000032:analysis*; D007797:Laminin / Q000032:analysis*; D009414:Nerve Growth Factors; D009442:Neurilemmoma / Q000032:analysis*; D010455:Peptides / Q000032:analysis / Q000302:isolation & purification*; D011509:Proteoglycans / Q000032:analysis*; D051381:Rats
D002807:Chondroitin; D002809:Chondroitin Sulfates; D006025:Glycosaminoglycans; D006497:Heparan Sulfate; D007797:Laminin; D009414:Nerve Growth Factors; D010455:Peptides; D011509:Proteoglycans; C047805:neurite-inducing factor