PhD Studentship: Integrated Analysis of Chemical Induced Lysosomal Cytotoxicity

Supervisor

Dr Patrick Lewis, plewis@rvc.ac.uk, Professor of Neuroscience, Royal Veterinary College

Project Details

The aim of this project is to identify, characterise, and dissect the events that result in lysosomal dysfunction and cytotoxicity following cellular small molecule drug exposure. 

Lysosomes are the key catabolic organelle in eukaryotic cells, responsible for degrading and recycling cellular components to maintain homeostasis. Disruption of lysosomal function has a substantial impact on cellular function, with maintaining healthy lysosomes being a key component of healthy aging. Importantly, environmental exposure to small molecule toxins and drugs can result in lysosomal damage, causing cellular phospholipidosis (PLD). This lysosomal impairment results in reduced phospholipid catabolism with characteristic accumulation of lysosomal lipids in multi-lamellar bodies observable by transmission electron microscopy (TEM). The underlying mechanisms of drug induced PLD are poorly understood. PLD is most commonly observed for compound with cationic and amphiphilic groups in the molecular scaffold. Compound with such characteristics were demonstrated to accumulate in lysosomes and are thought to interact with negatively charged phospholipids in the inner-lysosomal membrane, preventing docking of phospholipases involved in the catabolism. The physicochemical calculation of pKa and CLogP to predict phospholipidosis- inducing potential proposed by Ploemen et al. (2004) is widely used in the pharmaceutical development process as it provides a basis for in silico prediction of lysosomal impairment potential. However, PLD phenotypes can also be observed for compounds not following this rationale, and PLD was demonstrated for neutral and zwitterionic compounds, indicating that such models are too simplistic to fully explain complex cellular processes. Other mechanisms for induction of PLD are likely to include inhibition of functional enzymes such as phospholipases, lipid transporter proteins, or other pharmacological interactions that are difficult to predict solely based on the chemical structure. Compounds inducing PLD outside of the predicted parameters often start showing lysosomal impairment in in vitro screens, which requires confirmation in vivo on a case-by-case basis. Investigating the underlying mechanism of the lysosomal impairment and identifying key protein driver of drug induced lysosomal impairment leading to PLD can be utilized in unravelling the confounding lysosomal biology. 

This project combines our collective expertise in developing and running high throughput screening assays and the evaluation of metabolic endpoints for the detection of lysosomal damage and cytotoxicity (AstraZeneca), with a profound knowledge of lysosomal biology to evaluate potential mechanisms of action (Lewis group Royal Veterinary College, https://www.rvc.ac.uk/about/our-people/patrick-lewis, and Eden group UCL Institute of Ophthalmology, https://profiles.ucl.ac.uk/5486).

This project will involve learning and applying bioinformatic approaches, include protein network analysis and investigating expression, cellular analyses, advanced imaging (including electron microscopy with Dr Eden), as well as compound screening and high content analysis at AstraZeneca. 

Using these transformative technologies, the project will allow the PhD student to test the hypothesis that there are common and convergent mechanisms and pathways for drug induced lysosomal dam