ets-2 Is a Target for an Akt (Protein Kinase B)/Jun N-Terminal Kinase Signaling Pathway in Macrophages of motheaten-viable Mutant Mice

Abstract

The transcription factor ets-2 was phosphorylated at residue threonine 72 in a colony-stimulating factor 1 (CSF-1)- and mitogen-activated protein kinase-independent manner in macrophages isolated from motheaten-viable (me-v) mice. The CSF-1 and ets-2 target genes coding for Bcl-x, urokinase plasminogen activator, and scavenger receptor were also expressed at high levels independent of CSF-1 addition to me-v cells. Akt (protein kinase B) was constitutively active in me-v macrophages, and an Akt immunoprecipitate catalyzed phosphorylation of ets-2 at threonine 72. The p54 isoform of c-jun N-terminal kinase–stress-activated kinase (JNK- SAPK) coimmunoprecipitated with Akt from me-v macrophages, and treatment of me-v cells with the specific phosphatidylinositol 3-kinase inhibitor LY294002 decreased cell survival, Akt and JNK kinase activities, ets-2 phosphorylation, and Bcl-x mRNA expression. Therefore, ets-2 is a target for phosphatidylinositol 3-kinase–Akt–JNK action, and the JNK p54 isoform is an ets-2 kinase in macrophages. Constitutive ets-2 activity may contribute to the pathology of me-v mice by increasing expression of genes like the Bcl-x gene that promote macrophage survival.

ACKNOWLEDGMENTS

We acknowledge Lori Nelsen for expert technical assistance; Paul Herman (Ohio State University [OSU]) for critical discussions; Clay Marsh, Anil Jacobs, and Mark Coggeshall (OSU) for advice on Akt immune kinase assays; Gabriel Nunez (University of Michigan) for the gift of the mouse Bcl-x plasmids; Phil Tsichlis (Thomas Jefferson University) for Akt antibody and plasmids; the OSU Comprehensive Cancer Center; and the Keck Genetic Facility.

J.K.H. was supported by a Fellowship from the Lymphoma Research Foundation of America, Inc., and by T-32 Oncology Training grant CA 09338-21. This work was supported by NIH grant RO1-CA-53271 (M.C.O.).

J.L.S. and A.E.S. contributed equally to this work.