Wu, T. S. | bioRxiv Science

bioRxiv2020

Identification of compounds producing non-visual photosensation via TrpA1 in zebrafish

ABSTRACTTRPA1 receptors sense chemical irritants, but they do not normally respond to light. Previous studies have identified compounds that confer photosensitivity onto vertebrate TRPA1. However, the pharmacology of TRPA1-mediated non-visual photosensation remains poorly understood. To identify novel compounds that affect this process, we screened a large chemical library for compounds that increased light-elicited motor activity in larval zebrafish. We found structurally diverse hit compounds that were photoreactive and produced specific behavioral phenotypes. A subset of these compounds required functional TRPA1 to produce behavioral phenotypes in vivo. These findings provide novel prototype compounds for controlling TRPA1 with light and improve our understanding of non-visual TRPA1-mediated photosensation.Competing Interest StatementThe authors have declared no competing interest.View Full Text

pharmacology and toxicology↗

bioRxiv2020

Robust Sequence Determinants of α-Synuclein Toxicity in Yeast Implicate Membrane Binding

Protein conformations are shaped by cellular environments, but how environmental changes alter the conformational landscapes of specific proteins in vivo remains largely uncharacterized, in part due to the challenge of probing protein structures in living cells. Here, we use deep mutational scanning to investigate how a toxic conformation of -synuclein, a dynamic protein linked to Parkinsons disease, responds to perturbations of cellular proteostasis. In the context of a course for graduate students in the UCSF Integrative Program in Quantitative Biology, we screened a comprehensive library of -synuclein missense mutants in yeast cells treated with a variety of small molecules that perturb cellular processes linked to -synuclein biology and pathobiology. We found that the conformation of -synuclein previously shown to drive yeast toxicity--an extended, membrane-bound helix--is largely unaffected by these chemical perturbations, underscoring the importance of this conformational state as a driver of cellular toxicity. On the other hand, the chemical perturbations have a significant effect on the ability of mutations to suppress -synuclein toxicity. Moreover, we find that sequence determinants of -synuclein toxicity are well described by a simple structural model of the membrane-bound helix. This model predicts that -synuclein penetrates the membrane to constant depth across its length but that membrane affinity decreases toward the C terminus, which is consistent with orthogonal biophysical measurements. Finally, we discuss how parallelized chemical genetics experiments can provide a robust framework for inquiry-based graduate coursework.

biochemistry↗