[CAS NO. 172889-26-8]  PP1

PP1 is a nano-molar inhibitor of Lck and FynT, inhibits anti-CD3-induced protein-tyrosine kinase activity in T cells (IC50, 0.5 μM), demonstrates selectivity for Lck and FynT over ZAP-70, and preferentially inhibits T cell receptor-dependent anti-CD3-induced T cell proliferation (IC50, 0. 5 μM) over non-T cell receptor-dependent phorbol 12-myristate 13-acetate/interleu-kin-2 (IL-2)-induced T cell proliferation. PP1 (1 μM) selectively inhibits the induction of the IL-2 gene, but not the granulocyte-macrophage colony-stimulating factor or IL-2 receptor genes. PP1 also inhibits Src (IC50, 170 nM) and Hck (IC50, 20 nM). PP1 is 50–100-fold less active in the inhibition of A-431 epidermal growth factor receptor autophosphorylation (IC50, 0.25 μM). PP1 also inhibits Kit and Bcr-Abl tyrosine kinases with IC50 of ∼75 nM and 1 μM, respectively. PP1 completely abrogates the proliferation of M07e cells in response to SCF with IC50 of 0.5–1 μM. PP1 (1 μM) inhibits SCF-induced c-Kit autophosphorylation in intact cells and blocks the activation of mitogen-activated protein kinase and Akt. PP1 inhibits the activity of mutant constitutively active forms of c-Kit (D814V and D814Y) found in mast cell disorders, and triggers apoptosis in the rat basophilic leukemia cell line RBL-2H3 that expresses mutant c-Kit. PP1 reduces the constitutive activation of signal transducer and activators of transcription 5 and mitogen-activated protein kinase and triggeres apoptosis in FDCP1 cells expressing Bcr-Abl.