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Crippa V, Sau D, Rusmini P, Boncoraglio A, Onesto E, Bolzoni E, Galbiati M, Fontana E, Marino M, Carra S, Bendotti C, De Biasi S, Poletti A.
The small heat shock protein B8 (HspB8) promotes autophagic removal of misfolded proteins involved in amyotrophic lateral sclerosis (ALS). Hum Mol Genet.
2010 Sep 1;19(17):3440-56.
PubMed Abstract
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Comment by: Claudio Hetz, Melissa Nassif
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Submitted 5 July 2010
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Posted 15 July 2010
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 I recommend this paper
Based on cellular and animal models of ALS, this work indicates that the expression of HspB8, a family member of small heat-shock proteins, prevents mutant SOD1 aggregation and increases its solubility and clearance, even when proteosome activity is inhibited. Of note, HspB8 expression has been previously related to distal hereditary motor neuropathy type 2 (dHMN) and autosomal-dominant Charcot-Marie-Tooth (CMT) disease type 2L, and other pathologies. Here, the authors show, using in vitro studies, that HspB8 expression results in enhanced autophagy-mediated clearance of mutant SOD1.
We and other groups have reported that genetic or pharmacological manipulations that enhance autophagy actually lead to a dramatic decrease in mutant SOD1 aggregation, reducing its neurotoxicity. Crippa and coauthors showed, using electron microscopy studies, that HspB8 may induce mutant SOD1 clearance in cellular and animal models of ALS by activating macroautophagy pathways. These protective effects may possibly be due to the formation of a protein complex between HspB8 and Bag3, which was...
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Based on cellular and animal models of ALS, this work indicates that the expression of HspB8, a family member of small heat-shock proteins, prevents mutant SOD1 aggregation and increases its solubility and clearance, even when proteosome activity is inhibited. Of note, HspB8 expression has been previously related to distal hereditary motor neuropathy type 2 (dHMN) and autosomal-dominant Charcot-Marie-Tooth (CMT) disease type 2L, and other pathologies. Here, the authors show, using in vitro studies, that HspB8 expression results in enhanced autophagy-mediated clearance of mutant SOD1.
We and other groups have reported that genetic or pharmacological manipulations that enhance autophagy actually lead to a dramatic decrease in mutant SOD1 aggregation, reducing its neurotoxicity. Crippa and coauthors showed, using electron microscopy studies, that HspB8 may induce mutant SOD1 clearance in cellular and animal models of ALS by activating macroautophagy pathways. These protective effects may possibly be due to the formation of a protein complex between HspB8 and Bag3, which was demonstrated to activate autophagy in others studies. In addition, the authors suggested that mutant SOD1 may actually be part of the same protein complex. Furthermore, the authors indicated that the clearance of TDP-43, a protein shown to aggregate in sporadic ALS, is also modulated by HspB8 expression.
In summary, this article confirms the relevance of autophagy as a protective mechanism in ALS, and identifies a new regulator of the pathway. Modulating HspB8 expression may have a therapeutic impact to treat ALS and other diseases related to protein misfolding.
 View all comments by Claudio Hetz
View all comments by Melissa Nassif |
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REAGENTS/MATERIAL:
Immunohistochemistry on mice spinal cord sections
The mice were analyzed using as primary antibodies: rabbit polyclonal antibody against HspB8 (from J. Landry, Canada),
mouse monoclonal anti-human SOD1 (MBL, Japan)
and mouse monoclonal anti-GFAP to detect astrocytes (Invitrogen, Carlsbad, CA, USA).
Fluorescence, immunofluorescence and microscopy on NSC34 cells
primary antibodies: mouse monoclonal anti-FLAG (Sigma Aldrich, St. Louis, MO, USA),
rabbit polyclonal anti-HspB8 antibody (from J. Landry) and
mouse monoclonal anti-ubiquitin (Santa Cruz, Santa Cruz, CA, USA).
Western blot analysis and filter retardation assay
The following primary and secondary antibodies were used:
(i) for YFPu, mouse monoclonal anti-GFP (Zymed, San Francisco, CA, USA);
(ii) for SOD1, rabbit polyclonal anti-Cu/Zn superoxide dismutase (SOD-100, Assay Designs, Plymouth Meeting, PA, USA); (iii) for TDP-43, mouse monoclonal anti-FLAG (M2) (Sigma),
(iv) for Actin, goat polyclonal anti-Actin (I-19, Santa Cruz);
(v) the rabbit polyclonal antibody against HspB8 (from J. Landry) or
(vi) the mouse monoclonal anti-c-Myc (9E10) (Santa Cruz) for HspB8;
(vii) for GFP-SOD1s, the peroxidase-labeled goat anti-GFP (Vector Laboratories, Burlingame, CA, USA);
(ix) the mouse monoclonal anti-ub (Santa Cruz) for ubiquitin.
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