Effects of nerve growth factor-induced differentiation on the heparan sulfate of PC12 pheochromocytoma cells and comparison with developing brain

We have examined the size, charge, and sulfation pattern of heparan sulfate in the cell-soluble fraction, membranes, and culture medium of PC12 pheochromocytoma cells cultured in the presence and absence of nerve growth factor (NGF) and compared the structural features of PC12 cell heparan sulfate to that of rat brain at several stages of early postnatal development. Nitrous acid degradation studies revealed significant differences in the distribution of N-sulfate and N-acetyl groups in heparan sulfate present in the PC12 cell-soluble fraction, membranes, and medium and demonstrated that NGF treatment led to an increased proportion of N-sulfated segments in the cell-associated heparan sulfate, although no such change was seen in that released into the culture medium. There was very little change in the N-sulfation of brain heparan sulfate during the first 30 days after birth. In brain, most of the heparan sulfate glucosamine residues are N-sulfated and yield predominantly di- and tetrasaccharide nitrous acid degradation products, whereas PC12 cell heparan sulfate contains large blocks of N-acetylglucosamine residues. There was very little difference in the overall charge or size (approximately 15,000 Da) of heparan sulfate chains between the different PC12 cell fractions or brain, although NGF treatment led to a decrease in the proportion of less-charged chains in the PC12 cell membranes and a small increase in molecular size. Our studies therefore demonstrate the presence in PC12 cells of several pools of heparan sulfate having different structural properties, and that significant alterations in the charge, size, and sulfation pattern of PC12 cell heparan sulfate accompany NGF-induced differentiation and neurite outgrowth.