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Purification of Hsp104, a Protein Disaggregase
Published on: September 30, 2011
Helix 3 is necessary and sufficient for prion protein's anti-Bax function
Stéphanie Laroche-Pierre1, Julie Jodoin, Andréa C LeBlanc
1Bloomfield Center for Research in Aging, Lady Davis Institute for Medical Research, Sir Mortimer B. Davis Jewish General Hospital, Montréal, Quebec, Canada.
Journal of Neurochemistry
|February 7, 2009
Summary
The prion protein's helix 3 is essential for its protective function against the Bax protein, offering a target for cancer and neurodegeneration therapies. This helix 3 region is both necessary and sufficient for this anti-Bax activity.
Area of Science:
- Molecular Biology
- Cell Biology
- Neuroscience
Background:
- The prion protein (PrP) has known functions beyond its role in prion diseases.
- Cytosolic PrP (CyPrP) exhibits protective effects against apoptosis.
- The Bcl-2 associated protein X (Bax) is a key mediator of apoptosis.
Purpose of the Study:
- To determine the specific structural elements of PrP responsible for its anti-Bax function.
- To elucidate the role of N-terminal repeats and alpha-helices in CyPrP's protective activity.
Main Methods:
- Structure-function analysis of CyPrP mutants in MCF-7 cells.
- Site-directed mutagenesis to substitute key amino acid residues in helix 3.
- Assessment of cell viability and apoptosis in response to Bax expression.
Main Results:
- Deletion of N-terminal octapeptide repeats (BORs) partially affected anti-Bax function, while deletion of helix 3 or C-terminal regions abolished it.
- Proline substitution of K204, V210, or E219 in helix 3 inhibited anti-Bax activity.
- Alanine substitution of K204 in helix 3 also prevented anti-Bax function, while V210 and E219 substitutions did not.
- Expression of PrP's helix 3 alone conferred anti-Bax activity in both cancer cells and human neurons.
Conclusions:
- The alpha-helix 3 of PrP is both necessary and sufficient for its protective function against Bax-mediated cell death.
- While BORs influence this function, helix 3 is the critical determinant.
- Helix 3 represents a potential molecular target for therapeutic intervention in conditions involving aberrant apoptosis, such as cancer and neurodegeneration.
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