Author Interviews

22 Nov Rare Mutation in the PCSK9 Gene Confers Long Healthy Life

MedicalResearch.com Interview with: [caption id="attachment_56017" align="alignleft" width="111"] Dr. Austin[/caption] Richard C. Austin, PhD Professor and Career Investigator of the Heart and Stroke Foundation of Ontario Amgen Canada Research Chair in Nephrology McMaster University and St. Joseph’s Healthcare Hamilton, Ontario, Canada MedicalResearch.com: What is the background for this study? What are the main findings? Response: A previous study published in 2011 by my collaborator, Dr. Michel Chretien at the IRCM, identified a rare mutation in the PCSK9, termed Q152H. Individuals harboring this mutation demonstrated dramatic reductions in their LDL cholesterol levels and had a significantly lower risk of CVD. Furthermore, individuals harboring the Q152H mutation showed increases in longevity with no evidence of other diseases such as liver disease, cancer and chronic kidney disease. This Q152H mutation was unique with only 4 families in Quebec shown to harbor this genetic variant. In terms of its effect on PCSK9 expression/activity, the mutation at Q152H was precisely at the cleavage site in PCSK9 necessary for its activation. As a result, the Q152H mutation fails to be cleaved and activated, thereby blocking its secretion into the circulation. This is why the Q152H mutation is considered a loss-of-function PCSK9 mutant. Given our lab's interest in endoplasmic reticulum (ER) stress and ER storage diseases, we began to collaborate with Drs. Chretien and Seidah at the IRCM to investigate whether this Q152H mutant, when overexpressed in liver cells, would cause ER stress and liver cell injury. This was based on the findings that the Q152H mutant does not undergo autocatalytic cleavage and its subsequent secretion from liver cells. It is well known in the literature that the accumulation of misfolded or inactive proteins in the ER gives rise to ER stress and cell injury/dysfunction. As a result, we initially showed to our surprise that overexpression of the Q152H mutant in liver cells failed to cause ER stress BUT increased the protein levels of several important ER chaperones, GRP78 and GRP94, known to PROTECT against liver cell injury/dysfunction. As part of our JCI study, we furthered these studies to examine the effect of the Q152H mutant when overexpressed in the livers of mice. This is where we demonstrated that the Q152H mutation showed protection against ER stress-induced liver injury/dysfunction.