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Transforming growth factor alpha attenuates the functional expression of AMPA receptors in cortical GABAergic neurons.

ABSTRACT: In the developing neocortex, brain-derived neurotrophic factor (BDNF) exerts a trophic activity to increase the expression and channel activity of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-type glutamate receptor subunits. Here, we demonstrate that the epidermal growth factor (EGF) receptor (ErbB1) ligands exert the opposite biological activity in cultured neocortical neurons. Subchronic stimulation of ErbB1 with transforming growth factor alpha (TGFalpha), EGF, or heparin-binding EGF (HB-EGF) down-regulated protein expression of the GluR1 AMPA receptor subunit in cultured neocortical neurons. In agreement, TGFalpha treatment decreased the Bmax of [3H] AMPA binding and GluR1 mRNA levels. Immunocytochemistry revealed that the decrease in GluR1 was most pronounced in multipolar GABAergic neurons. To examine the physiological consequences, we recorded AMPA-evoked currents as well as miniature excitatory postsynaptic currents in morphologically identified putative GABAergic neurons in culture. Subchronic TGFalpha treatment decreased AMPA-triggered currents as well as the amplitude and frequency of miniature excitatory postsynaptic currents. An ErbB1 tyrosine kinase inhibitor, PD153035, inhibited the TGFalpha effect. Moreover, TGFalpha counteracted the neurotrophic activity of BDNF on AMPA receptor expression. Co-application of TGFalpha with BDNF blocked the BDNF-triggered up-regulation of AMPA receptor expression and currents. These observations reveal a negative regulatory activity of the ErbB1 ligand, TGFalpha, which reduces the input sensitivity of cortical GABAergic neurons to attenuate their inhibitory function.

SUBMITTER: Namba H

PROVIDER: S-EPMC3683556 | biostudies-literature | 2006 Apr

REPOSITORIES: biostudies-literature

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Transforming growth factor alpha attenuates the functional expression of AMPA receptors in cortical GABAergic neurons.

Namba Hisaaki H Nagano Tadasato T Iwakura Yuriko Y Xiong Huabao H Jourdi Hussam H Takei Nobuyuki N Nawa Hiroyuki H

Molecular and cellular neurosciences 20060126 4

In the developing neocortex, brain-derived neurotrophic factor (BDNF) exerts a trophic activity to increase the expression and channel activity of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-type glutamate receptor subunits. Here, we demonstrate that the epidermal growth factor (EGF) receptor (ErbB1) ligands exert the opposite biological activity in cultured neocortical neurons. Subchronic stimulation of ErbB1 with transforming growth factor alpha (TGFalpha), EGF, or heparin- ...[more]

PMID: 16443372

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Project description:Radiation fibrosis of the lung is a late toxicity of thoracic irradiation. Epidermal growth factor (EGF) signaling has previously been implicated in radiation lung injury. We hypothesized that TGF-?, an EGF receptor ligand, plays a key role in radiation-induced fibrosis in lung. Mice deficient in transforming growth factor (TGF-?(-/-)) and control C57Bl/6J (C57-WT) mice were exposed to thoracic irradiation in 5 daily fractions of 6 Gy. Cohorts of mice were followed for survival (n ? 5 per group) and tissue collection (n = 3 per strain and time point). Collagen accumulation in irradiated lungs was assessed by Masson's trichrome staining and analysis of hydroxyproline content. Cytokine levels in lung tissue were assessed with ELISA. The effects of TGF-? on pneumocyte and fibroblast proliferation and collagen production were analyzed in vitro. Lysyl oxidase (LOX) expression and activity were measured in vitro and in vivo. Irradiated C57-WT mice had a median survival of 24.4 weeks compared to 48.2 weeks for irradiated TGF-?(-/-) mice (P = 0.001). At 20 weeks after irradiation, hydroxyproline content was markedly increased in C57-WT mice exposed to radiation compared to TGF-?(-/-) mice exposed to radiation or unirradiated C57-WT mice (63.0, 30.5 and 37.6 ?g/lung, respectively, P = 0.01). C57-WT mice exposed to radiation had dense foci of subpleural fibrosis at 20 weeks after exposure, whereas the lungs of irradiated TGF-? (-/-) mice were largely devoid of fibrotic foci. Lung tissue concentrations of IL-1?, IL-4, TNF-?, TGF-? and EGF at multiple time points after irradiation were similar in C57-WT and TGF-?(-/-) mice. TGF-? in lung tissue of C57-WT mice rose rapidly after irradiation and remained elevated through 20 weeks. TGF-?(-/-) mice had lower basal LOX expression than C57-WT mice. Both LOX expression and LOX activity were increased after irradiation in all mice but to a lesser degree in TGF-?(-/-) mice. Treatment of NIH-3T3 fibroblasts with TGF-? resulted in increases in proliferation, collagen production and LOX activity. These studies identify TGF-? as a critical mediator of radiation-induced lung injury and a novel therapeutic target in this setting. Further, these data implicate TGF-? as a mediator of collagen maturation through a TGF-? independent activation of lysyl oxidase.

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Transforming growth factor alpha attenuates the functional expression of AMPA receptors in cortical GABAergic neurons.

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Transforming growth factor alpha attenuates the functional expression of AMPA receptors in cortical GABAergic neurons.

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