BDNF stimulates expression, activity and release of tissue-type plasminogen activator in mouse cortical neurons

Pierre Magistretti, Jean-Luc Martin
1999
Article

Résumé

Brain-derived neurotrophic factor (BDNF) is a neurotrophic factor involved in neuronal development and synaptic plasticity. Although the physiological effects of BDNF have been examined in detail, target proteins which mediate its actions remain largely unknown. Here, we report that BDNF stimulates the expression of tissue-type plasminogen activator (tPA) in primary cultures of cortical neurons in a time- and concentration-dependent manner. Among the other members of the neurotrophin family, neurotrophin-4 (NT-4) and to a lesser extent neurotrophin-3 (NT-3) also increased tPA mRNA expression, while nerve growth factor (NGF) was devoid of any effect. Induction of tPA expression by BDNF is accompanied by an increase in the proteolytic activity of tPA associated with cortical neurons and a release of tPA into the extracellular space. Release of tPA induced by BDNF depends on extracellular Ca2+ since it is markedly reduced in the presence of ethylene glycol-bis(beta-aminoethylether)-N,N,N',N'-tetraacetic acid (EGTA). Up-regulation of tPA expression by BDNF is followed by the induction of plasminogen activator inhibitor 2 (PAI-2), an inhibitor of tPA. Together these results suggest that activation of tPA by BDNF may contribute to structural changes associated with neuronal development or synaptic plasticity.

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We have identified by two-dimensional polyacrylamide gel electrophoresis a protein known as stathmin which is phosphorylated in a time- and concentration-dependent manner in response to brain-derived neurotrophic factor (BDNF) in primary cultures of cortical neurons. We show that stathmin phosphorylation is preceded by the activation of mitogen-activated protein kinase (MAPK) isoforms p44 and p42. Moreover, the MAPK kinase inhibitor PD 098059, which inhibits MAPK activation, also markedly reduces BDNF-stimulated phosphorylation of stathmin, therefore suggesting that phosphorylation of stathmin is triggered by the activation of MAPK. Phosphorylation of stathmin is specific for BDNF since nerve growth factor does not stimulate MAPK and stathmin phosphorylation in cultured cortical neurons. Taken together, these results identify stathmin as a new target protein of BDNF, possibly involved in the development of cortical neurons.

1998

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