Changes in proteoglycan composition of F9 teratocarcinoma cells upon differentiation

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Abstract
Mouse teratocarcinoma cells (F9) were induced to differentiate by retinoic acid and then labeled with [3H]-glucosamine and [35S]-sulfate. Proteoglycans were then isolated from the plasma membranes and the culture medium by mild, dissociative, non-shear-dependent techniques. The undifferentiated cells were devoid of hyaluronic acid and contained negligible quantities of heparan sulfate, dermatan sulfate and chondroitin sulfate. Upon differentiation, the cells synthesized large amounts of hyaluronic acid and there was a 3-fold increase in the amount of membrane-bound sulfated proteoglycans. The differentiated cells also synthesized a proteoglycan (PGM-2) which was shed completely into the medium. It consisted of a large protein core with covalently linked sugar chains which were sulfated and had an approximate MW of 12,000. These sugar chains consisted of glucosamine and galactose in a molar ratio of 1:1 and contained a small quantity of mannose. Upon differentiation of the cells the amount of this molecule increased by 3-fold. This molecule was distinct from other proteoglycans since it was resistant to degradation by heparanase, chondroitinases, hyaluronidase and neuraminidase, but could be degraded by keratanase. Structurally it was very similar to keratan sulfate, consisting of alternating residues of (-Gal-GlcNAc-) in chains of .apprx. 20 such disaccharide units.