Journal Article

The BH4 domain of Bcl-X<sub>L</sub> rescues astrocyte degeneration in amyotrophic lateral sclerosis by modulating intracellular calcium signals

Francesca Martorana, Liliana Brambilla, Chiara F. Valori, Chiara Bergamaschi, Chiara Roncoroni, Eleonora Aronica, Andrea Volterra, Paola Bezzi and Daniela Rossi

in Human Molecular Genetics

Volume 21, issue 4, pages 826-840
Published in print February 2012 | ISSN: 0964-6906
Published online November 2011 | e-ISSN: 1460-2083 | DOI: http://dx.doi.org/10.1093/hmg/ddr513
The BH4 domain of Bcl-XL rescues astrocyte degeneration in amyotrophic lateral sclerosis by modulating intracellular calcium signals

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Collective evidence indicates that motor neuron degeneration in amyotrophic lateral sclerosis (ALS) is non-cell-autonomous and requires the interaction with the neighboring astrocytes. Recently, we reported that a subpopulation of spinal cord astrocytes degenerates in the microenvironment of motor neurons in the hSOD1G93A mouse model of ALS. Mechanistic studies in vitro identified a role for the excitatory amino acid glutamate in the gliodegenerative process via the activation of its inositol 1,4,5-triphosphate (IP3)-generating metabotropic receptor 5 (mGluR5). Since non-physiological formation of IP3 can prompt IP3 receptor (IP3R)-mediated Ca2+ release from the intracellular stores and trigger various forms of cell death, here we investigated the intracellular Ca2+ signaling that occurs downstream of mGluR5 in hSOD1G93A-expressing astrocytes. Contrary to wild-type cells, stimulation of mGluR5 causes aberrant and persistent elevations of intracellular Ca2+ concentrations ([Ca2+]i) in the absence of spontaneous oscillations. The interaction of IP3Rs with the anti-apoptotic protein Bcl-XL was previously described to prevent cell death by modulating intracellular Ca2+ signals. In mutant SOD1-expressing astrocytes, we found that the sole BH4 domain of Bcl-XL, fused to the protein transduction domain of the HIV-1 TAT protein (TAT-BH4), is sufficient to restore sustained Ca2+ oscillations and cell death resistance. Furthermore, chronic treatment of hSOD1G93A mice with the TAT-BH4 peptide reduces focal degeneration of astrocytes, slightly delays the onset of the disease and improves both motor performance and animal lifespan. Our results point at TAT-BH4 as a novel glioprotective agent with a therapeutic potential for ALS.

Journal Article.  9659 words.  Illustrated.

Subjects: Genetics and Genomics

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