Helix 3 is necessary and sufficient for prion protein's anti-Bax function.
To identify the structural elements of the prion protein (PrP) necessary for its protective function against Bcl-2 associated protein X (Bax), we performed structure-function analyses of the anti-Bax function of cytosolic PrP (CyPrP) in MCF-7 cells. Deletions of 1, 2, or 3 N-terminal Bcl-2 homology domain 2-like octapeptide repeats (BORs), but not deletion of all four BORs, abolish CyPrPs anti-Bax function. Deletion of alpha-helix 3 (PrP23-199) or further C-terminal deletions of alpha-helix 1 and 2, and beta-strand 1 and 2 (PrP23-172, PrP23-160, PrP23-143, and PrP23-127) eliminates CyPrPs protection against Bax-mediated cell death. The substitution of helix 3 amino acid residues K204, V210, and E219 by proline inhibits the anti-Bax function of CyPrP. The substitution of K204, but not V210 and E219, by alanine residues also prevents CyPrPs anti-Bax function. Expression of PrPs helix 3 displays anti-Bax activity in MCF-7 cells and in human neurons. Together, these results indicate that although the BOR domain has an influence on PrPs anti-Bax function, the helix 3 is necessary and sufficient for the anti-Bax function of CyPrP. Identification of helix 3 as the structural element for the anti-Bax function thus provides a molecular target to modulate PrPs anti-Bax function in cancer and neurodegeneration.
Laroche-Pierre
Stéphanie
S
Bloomfield Center for Research in Aging, Lady Davis Institute for Medical Research, Sir Mortimer B. Davis Jewish General Hospital, Montréal, Quebec, Canada.
Jodoin
Julie
J
LeBlanc
Andréa C
AC
D000409:Alanine / Q000737:chemistry; D000595:Amino Acid Sequence / Q000502:physiology; D019943:Amino Acid Substitution / Q000502:physiology; D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D019610:Cytoprotection / Q000235:genetics; D006801:Humans; D051379:Mice; D009369:Neoplasms / Q000235:genetics / Q000378:metabolism; D009410:Nerve Degeneration / Q000235:genetics / Q000378:metabolism; D018621:PrPC Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D017096:Prion Diseases / Q000235:genetics / Q000378:metabolism / Q000503:physiopathology; D011392:Proline / Q000737:chemistry; D017433:Protein Structure, Secondary / Q000235:genetics; D051028:bcl-2-Associated X Protein / Q000235:genetics / Q000378:metabolism*
D018621:PrPC Proteins; D051028:bcl-2-Associated X Protein; D011392:Proline; D000409:Alanine