Pit formation and rapid changes in surface morphology of sympathetic neurons in response to nerve growth factor.

Abstract

Scanning and transmission electron microscope studies were carried out on the rapid cell surface responses of cultured newborn rat sympathetic neurons to nerve growth factor (NGF), a substance that promotes their survival and differentiation. The somas of sympathetic neurons continuously exposed to NGF or deprived of the factor for 4-5 h have a very smooth surface. After readdition of NGF to the latter type of cultures, there is rapidly initiated a transient, sequential change in the cell surface. Microvilli and small ruffles appear within 30 s and are most prominent by 1 min. By 3 min of exposure, the microvilli and ruffles decrease in prominence, and by 7 min the somal surface is again smooth. By 30 s after NGF readdition, as increase in the number of 60- tp 130-nm coated pits is also detectable. This increase reaches a maximum of about threefold from 0.5 to 3 min and then gradually decreases. Alterations in the surface did not occur on the nonneuronal cell types present in the cultures and were not observed in response to another basic protein (cytochrome c) or to physical manipulation. Changes in cell surface architecture induced by NGF in normal sympathetic neurons and, as previously described, in PC12 pheochromocytoma cells indicate that such responses may present or reflect primary events in the mechanism of the factor's action.

NGF Signals through TrkA to Increase Clathrin at the Plasma Membrane and Enhance Clathrin-Mediated Membrane Trafficking

“…In the same experiments we noted that NGF treatment markedly increased clathrinimmunostained puncta at or near the plasma membrane . Although consistent with earlier, as well as more recent, observations on the effect of NGF, EGF, and insulin (Connolly et al, 1981(Connolly et al, , 1984Corvera, 1990;Wilde et al, 1999), the extent of the change and its rapidity were impressive. Quite unexpectedly, we also found that most (ϳ80%) clathrin puncta near the surface of NGF-treated cells failed to stain for TrkA, suggesting that clathrin was recruited to membranes containing little or no TrkA.…”

“…How the interaction of these components is regulated is of considerable interest. It has been known for some time that polypeptide growth factor signals influence the formation of coated membranes (Connolly et al, 1981(Connolly et al, , 1984. Greene and colleagues showed in PC12 cells treated with NGF that the number of clathrin-coated plasma membrane densities increased two-to threefold within 30 sec of NGF addition (Connolly et al, 1981).…”

Assembly of endocytic machinery around individual influenza viruses during viral entry

“…Ligand-induced clathrin-redistribution to the plasma membrane has been previously reported for epidermal growth factor (EGF) and nerve growth factor (NGF) 43 . There, the binding of EGF to its receptor causes phosphorylation of the clathrin heavy chain and a global redistribution of clathrin to the cell periphery to form CCPs 44 .…”

Endocytosis of influenza viruses

“…While ligand-induced clathrin-redistribution to the plasma membrane has been previously reported for epidermal growth factor (EGF) and nerve growth factor (NGF) [41], these cases involve global changes in the distribution of clathrin in the cell. The binding of EGF to its receptor causes phosphorylation of the clathrin heavy chain and a global redistribution of clathrin to the cell periphery [42].…”