A NOVEL TYROSINE KINASE-ACTIVITY IN THE COTTON LEAFWORM, SPODOPTERA-LITTORALIS

A rapid, highly-specific ELISA for tyrosine kinases readily detects su ch activity in crude extracts prepared from rat mammary epithelial and fibroblastic cells that have been stimulated with epidermal growth fa ctor or basic fibroblast growth factor. Tyrosine kinase activity is al so found in extracts of pupae of the cotton leafworm, Spodoptera litto ralis. Both the mammalian and the insect tyrosine kinases are ATP-depe ndent. Both cytosol and membrane-associated (Triton-X-100-soluble) fra ctions 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 geniste in and an analogue of erbstatin: methyl 2,5-dihydroxycinnamate. Howeve r, the tyrosine kinase activities present in pupae of Spodoptera litto ralis 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.