A novel tyrosine kinase activity in the cotton leafworm, Spodoptera littoralis

A rapid, highly-specific ELISA for tyrosine kinases readily detects such activity in crude extracts prepared from rat mammary epithelial and fibroblastic cells that have been stimulated with epidermal growth factor or basic fibroblast growth factor. Tyrosine kinase activity is also found in extracts of pupae of the cotton leafworm, Spodoptera littoralis. Both the mammalian and the insect tyrosine kinases are ATP-dependent. Both cytosol and membrane-associated (Triton-X-100-soluble) fractions of Spodoptera littoralis pupae contain tyrosine kinase activity. The growth factor-stimulated tyrosine kinase activities in extracts of growth factor-stimulated rat mammary cells are inhibited by genistein and an analogue of erbstatin: methyl 2,5-dihydroxycinnamate. However, the tyrosine kinase activities present in pupae of Spodoptera littoralis are not sensitive to these inhibitors, suggesting that the major tyrosine kinases of Spodoptera littoralis pupae may be distinct from the growth factor-stimulated mammalian tyrosine kinases.