[Studies on the regulation of glycolipid sulfotransferase activity in human renal cancer cells].
In the previous studies, epidermal growth factor (EGF) was found to elevate glycolipid sulfotransferase activity in a human renal cell carcinoma cell line, SMKT-R3. To elucidate whether Ras is involved in the signal transduction pathway from EGF to the expression of the sulfotransferase, effects of EGF and a tyrosine kinase inhibitor on the sulfotransferase activity were investigated in renal cancer cells stably expressing activated Ras. SMKT-R3 cells were transfected with a plasmid carrying v-H-ras (pv-H-ras). As a control, SMKT-R3 cells transfected with a mutant v-H-ras, in which glycine at position 15 was replaced by valine (pG15V), was used. The expression of v-H-ras in transfected cells was examined by RT-PCR analysis. Two clones transfected with pv-H-ras, named A1 and A6, and two clones transfected with pG15 V, termed B1 and B4, were found to express v-H-ras and G15V genes, respectively, and employed in the following experiments. Though EGF elevated the activity of glycolipid sulfotransferase in B1, B4 and SMKT-R3 cells, it did not change the activity levels in A1 and A6 cells. This result suggested that since the signal from Ras was saturated in the cells expressing activated Ras, the cells did not respond to the stimulation by EGF. To know the association between tyrosine kinase of EGF receptor and Ras, the effect of Genistein, a specific inhibitor of tyrosine kinase, on the sulfotransferase activity was examined in these cell lines. Genistein reduced the activity of glycolipid sulfotransferase in B1, B4, and SMKT-R3 cells, whereas it hardly affected the sulfotransferase activity in A1 and A6 cells. This result indicated that the signal from tyrosine kinase was dissociated from the regulation of the sulfotransferase activity in the cells expressing activated Ras. These observations suggest that Ras is involved in the signal transduction from EGF to the expression of glycolipid sulfotransferase activity in SMKT-R3 cells and acts in the downstream of tyrosine kinase of EGF receptor.
Yabunaka
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Department of Rehabilitation and Physical Medicine, Hokkaido University School of Medicine, Sapporo, Japan.
D000595:Amino Acid Sequence; D001483:Base Sequence; D002292:Carcinoma, Renal Cell / Q000201:enzymology* / Q000235:genetics; D004815:Epidermal Growth Factor / Q000494:pharmacology; D066246:ErbB Receptors; D015971:Gene Expression Regulation, Enzymologic; D011905:Genes, ras; D019833:Genistein; D006801:Humans; D007529:Isoflavones / Q000494:pharmacology; D007680:Kidney Neoplasms / Q000201:enzymology* / Q000235:genetics; D008969:Molecular Sequence Data; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D015398:Signal Transduction; D015238:Sulfotransferases / Q000378:metabolism*; D014162:Transfection; D014407:Tumor Cells, Cultured
D007529:Isoflavones; D004815:Epidermal Growth Factor; D019833:Genistein; D066246:ErbB Receptors; D011505:Protein-Tyrosine Kinases; D015238:Sulfotransferases; C020556:galactosylceramide sulfotransferase