FUNCTIONAL ANALYSIS OF PHOSPHOLIPASE D3 (PLD3) IN ALZHEIMER´S DISEASE
Alzheimer´s disease (AD) is the most common form of progressive dementia in the elderly, for which several genetic risk factors have been described. Previously, a whole-exome sequencing study identified that a rare coding variant in the phospholipase D3 (PLD3) gene confers a two-fold risk factor in the development of AD, affecting the turnover and cleavage products of the Amyloid Precursor Protein (APP). PLD3 contains two conserved HKD motifs. As a result, it has been classified as a member of the phospholipase D family, together with the well characterized phospholipases D1 and D2. However, to date, no canonical activity or substrate has been described for PLD3.
Our group has described PLD3 as a transmembrane protein transported throughout the secretory and endocytic pathway. In early endosomal compartments, PLD3 co-localizes with APP. PLD3 is then proteolytically processed to a soluble form in acidic compartments to finally reach lysosomes. Our data indicate that PLD3 transport to lysosomes is mediated via the endosomal sorting complex required for transport (ESCRT) where previous ubiquitination of lysine residues is required for sorting into intraluminal vesicles (ILVs).
In brains derived from Pld3-deficient mice no changes of APP full length levels nor its cleavage products, including amyloid beta (Aß), were found. However, microgliosis in the dentate gyrus of the hippocampus together with a depression-like behavior was observed. As part of this project our Pld3 KO mouse will be bred into an established AD mouse model (Pld3-/-5xFAD). We believe that the AD-related phenotypes of this well described mouse strain will help us to decipher the effect of the absence of Pld3 on the turnover, transport and processing of APP, by performing cell biology and biochemical approaches, e.g. culture of primary neurons and immunohistochemistry. Previous data have shown that APP is also ubiquitinated and transported to ILVs via de ESCRT pathway to further be degraded in lysosomes, therefore, ubiquitination and MVB-dependent sorting of Pld3 in cell lines and primary neurons will be also investigated.
We hypothesize that Pld3 affects the sorting of APP in late endosomal-/lysosomal compartments and thereby its proteolytic cleavage and degradation is affected leading to an accumulation of Aß plaques and further increasing the probability to develop AD.
|Name||Adriana Carolina González|
|Date of Birth||
|since 2015||PhD student. Functional characterization of new membrane-associated lysosomal proteins. Institute of Biochemistry. Unit of Molecular Cell Biology and Transgenic Research. Christian Albrecht Universität zu Kiel, Germany|
|2012 - 2015||
Master of Science Degree in Molecular Cell Biology and Neurobiology, Department of Human Biology and Human Genetics, University of Kaiserslautern, Germany
|2005 - 2010||Diploma in Biology at Simon Bolivar University, Caracas, Venezuela|