AR and ER interaction with a p21-activated kinase (PAK6).
A human protein termed p21-activated kinase 6 (PAK6), based on homology to the PAK family of serine/threonine kinases, was cloned as an AR interacting protein. PAK6 was a 75-kDa protein with a predicted N-terminal Cdc42/Rac interactive binding domain and a C-terminal kinase domain. PAK6 bound strongly to GTP-Cdc42 and weakly to GTP-Rac. In contrast to most PAKs, kinase activity was not stimulated by Cdc42 or Rac, but could be stimulated by AR binding. PAK6 interacted with the intact AR in a mammalian one-hybrid assay and bound in vitro, without ligand, to the hinge region between the AR DNA- and ligand-binding domains. PAK6 also bound to the ERalpha, and binding was enhanced by 4-hydroxytamoxifen. AR and ERalpha transcriptional activities were inhibited by PAK6 in transient transfections with episomal and integrated reporter genes. AR inhibition was not reversed by transfection with an activated Cdc42 mutant, Cdc42V12, which by itself also inhibited AR transactivation. Epitope-tagged PAK6 was primarily cytoplasmic in the absence or presence of AR and hormone. PAK6 transcripts were expressed most highly in brain and testis, with lower levels in multiple tissues including prostate and breast. PAK6 interaction provides a mechanism for cross-talk between steroid hormone receptors and Cdc42-mediated signal transduction pathways and could contribute to the effects of tamoxifen in breast cancer and in other tissues.
Lee
Suzanne R
SR
Cancer Biology Program, Hematology-Oncology Division, Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts 02215, USA.
Ramos
Sharon M
SM
Ko
Andrew
A
Masiello
David
D
Swanson
Kenneth D
KD
Lu
Michael L
ML
Balk
Steven P
SP
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001921:Brain / Q000502:physiology; D002478:Cells, Cultured; D003001:Cloning, Molecular; D047628:Estrogen Receptor alpha; D006801:Humans; D008297:Male; D008322:Mammals; D008969:Molecular Sequence Data; D009154:Mutation; D009928:Organ Specificity; D017346:Protein Serine-Threonine Kinases / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism*; D011944:Receptors, Androgen / Q000235:genetics / Q000378:metabolism*; D011960:Receptors, Estrogen / Q000235:genetics / Q000378:metabolism*; D017421:Sequence Analysis; D017386:Sequence Homology, Amino Acid; D013629:Tamoxifen / Q000031:analogs & derivatives* / Q000494:pharmacology; D013737:Testis / Q000502:physiology; D014158:Transcription, Genetic; D020764:cdc42 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism; D054462:p21-Activated Kinases; D020744:rac GTP-Binding Proteins / Q000378:metabolism
D047628:Estrogen Receptor alpha; D011944:Receptors, Androgen; D011960:Receptors, Estrogen; D013629:Tamoxifen; C016601:afimoxifene; C429007:PAK6 protein, human; D017346:Protein Serine-Threonine Kinases; D054462:p21-Activated Kinases; D020764:cdc42 GTP-Binding Protein; D020744:rac GTP-Binding Proteins