STAT3 as a downstream mediator of Trk signaling and functions.
Signal transducer and activator of transcription 3 (STAT3) has long been shown to regulate gene transcription in response to cytokines and growth factors. Recent evidence suggests that STAT3 activation may also occur downstream of receptor-tyrosine kinase activation. In the current study we have identified STAT3 as a novel signal transducer for TrkA, the receptor-tyrosine kinase that mediates the functions of nerve growth factor (NGF). Activation of TrkA by NGF triggered STAT3 phosphorylation at Ser-727, and enhanced the DNA binding and transcriptional activities of STAT3. More importantly, neurotrophin-induced increase in STAT3 activation was observed to underlie several downstream functions of neurotrophin signaling. First of all, knockdown of STAT3 expression using the RNA interference approach attenuated NGF-induced transcription of immediate early genes in PC12 cells. Furthermore, reduced STAT3 expression in PC12 cells suppressed NGF-induced cyclin D1 expression, thereby inhibiting growth arrest normally triggered by NGF treatment. Finally, inhibition of STAT3 expression decreased brain-derived neurotrophic factor-promoted neurite outgrowth in primary hippocampal neurons. Together, our findings have identified STAT3 as an essential component of neurotrophin signaling and functions.
Ng
Yu Pong
YP
Department of Biochemistry, Biotechnology Research Institute, and Molecular Neuroscience Center, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China.
Cheung
Zelda H
ZH
Ip
Nancy Y
NY
D000818:Animals; D001483:Base Sequence; D019208:Brain-Derived Neurotrophic Factor / Q000494:pharmacology; D002478:Cells, Cultured; D017931:DNA Primers; D006624:Hippocampus / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D007150:Immunohistochemistry; D020932:Nerve Growth Factor / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D016716:PC12 Cells; D010766:Phosphorylation; D051381:Rats; D020917:Receptor, trkA / Q000378:metabolism*; D050796:STAT3 Transcription Factor / Q000378:metabolism / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*; D013347:Subcellular Fractions / Q000378:metabolism; D014158:Transcription, Genetic / Q000502:physiology
D019208:Brain-Derived Neurotrophic Factor; D017931:DNA Primers; D050796:STAT3 Transcription Factor; D020932:Nerve Growth Factor; D020917:Receptor, trkA