By traditional definition, brain-derived neurotrophic factor (BDNF) was initially identified to mediate cell proliferation, differentiation and apoptosis in the nervous system. Recently, a large body of evidence strongly suggested an essential role of BDNF in regulating neuroplasticity, including long-term potentiation (LTP) and learning and memory. Importantly, BDNF expression is tightly regulated by neuronal activity. Molecular analysis of its promoter regions (promoter 1 and 3, or P1 and P3) has revealed several calcium-responsive elements (CaREs), indicating that BDNF transcription may be induced by Ca, the major second messenger in neurons. In addition, a number of transcription factors, such as CREB, CaRF and USF, were identified to bind different CaRE. The existence of these multiple control elements in BDNF promoters is believed to achieve specific regulation in different populations of neurons and upon different neuronal activities. We found that CREB- and CaRF-mediated transcription was differentially regulated by PKA and ERK. Knowing that both PKA and ERK activity are induced by Ca and neuronal activity, we hypothesize that P1 and P3 are specifically activated by neural activity in a tissue specific manner, and differentially regulated by different Ca-stimulated protein kinases. Although the role of PKA, ERK and calmodulin-dependent kinases (CaMK) were implicated in CREB-mediated transcription, their function in regulating native BDNF promoters is not clear. It is also not clear which promoter is regulated by neural activities in intact animals. Furthermore, the in vivo regulator for the activity-dependent BDNF up-regulation is unknown. We will measure reporter gene expression under the control of the individual CaRE or native P1 and P3. The effects of Ca-stimulated kinases will be tested by using inhibitors, dominant negative form of the individual kinase, and in neurons from mutant mice. BDNF expression will be examined in cultured neurons, brain slices, and intact animals after training for certain learning-related behavioral paradigms. Importantly, the physiological relevance of BDNF will also be addressed with mutant and aged mice. Because abnormal BDNF expression has been implicated in aging, depression, stress, and neurological diseases, the proposed study will not only enhance the general understanding on gene expression in neuroplasticity, but also may lead to the development of a potential neurotherapeutic.
Showing the most recent 10 out of 15 publications
