A whole-animal small molecule screen to identify and characterize modifiers of Apolipoprotein B - PROJECT SUMMARY
Metabolic syndrome, encompassing type 2 diabetes, non-alcoholic fatty-liver disease, and cardiovascular
disease, affects more than one billion people worldwide. While its etiology is complex, the best biological marker
of metabolic syndrome is increased levels of apolipoprotein B (ApoB)-containing lipoproteins (B-lps). B-lps
transport triglycerides and cholesterol through the plasma to peripheral tissues, and excess plasma B-lps are
causative to metabolic syndrome. A single ApoB molecule decorates each B-lp and is essential for its function.
However, the cellular mechanisms that ultimately regulate ApoB and B-lp production, secretion, transport, and
degradation remains to be fully defined. The proposed studies aim to identify new molecules that alter B-lp
physiology with the hope of not only generating new therapeutics but to elucidate new cell biological mechanisms
of ApoB regulation. Human B-lp biology is remarkably conserved in the zebrafish. Further, zebrafish produce
large numbers of progeny, larvae are optically transparent, and larvae do not require an exogenous food source.
Thus, the zebrafish is the ideal model to identify novel mechanisms of ApoB modulation. Therefore, the Farber
lab generated an in vivo chemiluminescent reporter of ApoB that does not disrupt ApoB function. Thus, I
hypothesize that I can identify novel drugs that modulate ApoB regulation, turnover, and function to rectify
metabolic dysfunction using this whole-animal reporter of ApoB. I have developed a high-throughput assay to
screen chemiluminescence from whole zebrafish. Each compound that reduces ApoB from a drug repurposing
library will be further validated by several assays measuring ApoB and B-lps production, size, and turnover. I will
also evaluate the effects of each compound on whole-animal physiology. My screening efforts have identified 25
ApoB-lowering compounds. One compound, pimethixene maleate, specifically reduces ApoB levels in a dose-
dependent manner. Prior research suggests pimethixene is a serotonin receptor antagonist. Studies suggest
that serotonin influence B-lps levels through regulation of the mammalian Target of Rapamycin (mTOR). Thus,
I hypothesize that pimethixene-dependent ApoB reduction is mediated by 5-HT2 receptor antagonism. I will
determine whether pimethixene directly alters this pathway. Further, I will examine whether this compound
improves several risk factors associated with metabolic disease using a series of established transgenic reporter
lines and bioinformatic approaches. Ultimately, this research aims not only to identify novel ApoB-modulating
therapeutics that would improve outcomes of metabolic disease but would also provide fundamental insights into
the regulation and function of ApoB. Together, the research environment of the Farber lab and the Carnegie
Institute are ideal for the success of this project and my success in the future as I grow towards an independent
career in metabolism research.
