Research Projects

Rationale: The auxin signaling is well-known for its involvement in plant, its function in non-plant species remains poorly understood due to lack of evidence for auxin binding and transport proteins. Recently, we have discovered an auxin transporter, GPR155, also known as LYCHOS (Lysosomal Cholesterol Signaling), which is a unique lysosomal membrane transceptor that combines GPCR domain with transporter domains1. More specifically, we have demonstrated that GPR155 is crucial for cholesterol signaling and auxin transport within lysosomes, functioning as a cholesterol sensor that activates mTORC1 in a cholesterol-dependent manner. Studies, have shown that aberrant trafficking and malfunctioning of this lysosomal transceptor are implicated in various neurological disorders and numerous, including Alzheimer’s disease. Accordingly, an increased understanding of molecular mechanisms underlying GPR155's roles as a sensor of cholesterol and auxin signaling in shaping neuronal function will greatly enhance knowledge essential for developing new therapeutic strategies. However, the mechanistic insights into the molecular mechanisms of the GPR155 nanosignaling complex, particularly regarding auxin transport and cholesterol sensing in spatiotemporal regulation of lysosome in neurons remained poorly understood, hampering therapeutic design. We believe that exploring the non-canonical auxin-cholesterol signaling axis in neurons could unlock new therapeutic avenues for treating neurological disorders. To address this knowledge gap, we propose the following objectives: AIM 1. Determine the mechanism by which GATOR1, G-proteins, and cholesterol modulate auxin transport by GPR155 into lysosome. AIM 2. Elucidating the spatiotemporal regulation of mTORC1-lysosome interactions by GPR115-mediated auxin signaling. AIM 3. Structural determinants of auxin and cholesterol signaling. A completion of these objectives is poised to be transformative, as we will identify crucial interactions and factors essential for efficient cholesterol sensing and auxin transport in lysosomes and its spatiotemporal positioning in neurons, revealing new pathways and mechanisms with significant implications for cellular neurological conditions. Methodology: We will employ electrophysiology and lipid bilayer reconstitution to investigate auxin transport and assess how cholesterol binding influences auxin permeation. To elucidate the structural basis of auxin transport, cholesterol interaction, and the regulatory role of the GATOR1 complex, we will use cryo-electron microscopy (cryo-EM) to determine high-resolution structures of GPR155 in relevant functional states. Novelty: • Focus on GPR155 interactions involved transduction of auxin signals and analyzing multi-omics data for find pathogenic variants of GPR155 is an uncharted territory. • Characterizing poorly understood interactions of GPR155 transceptor will illuminate new biology of this well studied lysosomal receptor • Proposal aims to obtain high resolution of receptor assemblies not currently available for any of the constituent protein either alone or in complexes. Scientific Outcomes and Impact By understanding the molecular underpinnings of this pathway, we aim to develop targeted therapies that could mitigate the effects of these debilitating diseases and improve patient outcomes. Our research will provide important insights into the role of GPR155 and its interaction with cellular components, such as GATOR1 and G-proteins, to elucidate how these interactions influence lysosomal positioning and function under different cellular conditions. By visualizing and characterizing the nonsignaling complexes of GPR155, we hope to reveal novel insights into the regulation of lysosomal dynamics and their implications in neurological disorders. This knowledge will pave the way for the development of innovative therapeutic strategies aimed at modulating lysosomal function and signaling in disease contexts.