GLYCOSYLATION CHANGES IN ONCOGENESIS

The objective of this proposal is to determine the ability of
calpactins(p35 and p36), the substrates of protein tyrosine kinases
activated upon oncogenic transformation, to alter protein
glycosylation. Calpactin II has been identified as being
homologous to Lipocortin I, and inhibitor of Phospholipase A2, and
lipocortins have been shown to affect the glycosylation of IgE
growth factors released from T cells. The hypothesis to be tested
in this proposal is that the activation of protein tyrosine kinases
in the early steps of oncogenic transformation induces changes in
protein glycosylation related to the phosphorylation of
intracellular calpactins. The effect of calpactin/lipocortin or protein glycosylation in cell
culture will be determined for secreted and membrane-bound
glycoproteins. Changes in oligosaccharide structures induced by
calpactin/lipocortin treatment will be determined by direct
biochemical analysis. Phosphorylation of endogenous calpactin
II/p35 will be induced to determine its effect of protein
glycosylation. Finally, the mechanism of lipocortin induction of
changes in protein glycosylation will be studied. While changes in cellular protein glycosylation have been observed
upon oncogenic transformation, the types of changes resulting
from lipocortin treatment of cells have not been reported. This
project provides a new approach to the early changes that occur
at the cell surface as a result of oncogenesis. These results will
provide important information about the cellular changes induced
by protein tyrosine kinase activation and about the role of the
calpactin/lipocortin family in the process of oncogenic
transformation.