A specific type of ganglioside as a modulator of insulin-dependent cell growth and insulin receptor tyrosine kinase activity

Insulin-dependent cell growth has been correlated with insulin receptor function, particularly receptor-associated kinase activity, in in vitro studies. The insulin-dependent phosphorylation of the 95-kDa receptor subunit was clearly inhibited, in a concentration-dependent manner, by the presence of unbranched neolacto series gangliosides having a NeuAc2----3Gal terminus, particularly 2----3-sialosylparagloboside (2----3SPG; IV3NeuAc-nLc4), but not by other gangliosides with a NeuAc2----6Gal terminus or by branched neolacto series gangliosides (e.g. G10). Such inhibition of phosphorylation was minimal with ganglio series gangliosides and negligible with sphingosine, neutral glycolipids, or sulfatide. 2----3SPG did not affect insulin binding to the insulin receptor. Insulin-dependent cell growth and its inhibition by 2----3SPG were observed in three human cell lines so far tested: lymphoid cell line IM9, promyelocytic leukemia cell line HL-60, and erythroleukemia cell line K562. Since IM9 cells contain a much higher quantity of insulin receptor than do HL-60 or K562 cells, insulin-dependent receptor phosphorylation and its inhibition by 2----3SPG in intact cells were clearly observed with IM9 cells. Receptor phosphorylation in intact cells was inhibited when cells were preincubated in the presence of 2----3SPG. Insulin-dependent growth of HL-60 and K562 cells was also inhibited by prolonged culture (96-144 h) with exogenous 2----3SPG. Subsequent to the inhibition of insulin-dependent HL-60 cell growth, a remarkable phenotypic transformation was observed, i.e. changes in morphology, enzymes, and cell-surface markers to those characteristic of monocytes. The level of 2----3SPG in HL-60 cells increased when cells were cultured with 1 alpha,25-dihydroxyvitamin D3 to the same degree seen in cells cultured with 5 microM 2----3SPG. Both these treatments led to inhibition of insulin-dependent cell growth, followed by induction of monocytic differentiation. Thus, the cellular level of 2----3SPG may modulate insulin-dependent cell growth and define the lineage specificity of differentiation through modulation of receptor-associated kinase activity.