This project investigates how TRPML1 regulates interaction between mitochondria and lysosoms during cancer energy stress, focusing on ion signaling at nanoscale contact sites and dynamic mitochondrial ultrastructure organization. Structured illumination microscopy will connect mitochondrial membrane potential patterns with organelle organization in living cells. The project addresses fundamental mechanisms of organelle communication in cancer.
Project Details
Background:
Cells adapt to metabolic stress by reorganizing their organelles, and some of the most critical decisions happen at nanoscale contact sites between mitochondria and lysosomes. These contact sites act as highly dynamic signaling hubs that coordinate ion fluxes, energy production, and organelle quality control. In cancer cells, where energy stress is common, understanding how these interactions are regulated at the level of individual organelles and even single molecules is a major open challenge.
Our recent work shows that mitochondrial cristae junctions are not static structures: they can open to allow proton leakage, reshaping local membrane potential and metabolic output1,2. This process is tightly regulated by mitochondrial Ca²⁺ uptake through the MCU complex and its gatekeeper MICU13. Intriguingly, TRPML1, a lysosomal Ca²⁺ channel best known for maintaining lysosomal ion homeostasis, appears to directly influence mitochondrial Ca²⁺ signaling specifically at lysosome–mitochondria contact sites4. How TRPML1-mediated ion fluxes reshape mitochondrial ultrastructure and function in stressed cancer cells is largely unknown and ideally suited for investigation using single-cell and super-resolution microscopy.
Hypothesis and Objectives:
We hypothesize that metabolic stress enhances lysosome–mitochondria coupling in cancer cells, and that TRPML1-dependent ion signaling at these contact sites actively remodels mitochondrial structure, membrane potential gradients, and bioenergetic performance. These processes are expected to be highly heterogeneous and dynamic at the single-cell and sub-organelle level.
Methodology:
During the first phase of the project, the student will establish live-cell imaging approaches using genetically encoded biosensors for Ca²⁺, pH, K⁺, and reactive oxygen species targeted to lysosomes and defined mitochondrial subcompartments. By combining these tools with pharmacological activation of TRPML1, the student will characterize how ion fluxes and metabolic stress reshape lysosome–mitochondria communication in single cancer cells.
In the second phase, the project will leverage super-resolution and ultrafast confocal microscopy in living cells to investigate how TRPML1 regulates lysosomal acidification, mitophagy, and the dynamics of mitochondrial cristae at contact sites. Structured illumination microscopy1-3 will be used to resolve spatial gradients in mitochondrial membrane potential, allowing functional readouts to be directly linked to nanoscale organelle organization.
In the final phase, confocal super-resolution PAINT microscopy and single-molecule tracking will be established to probe mitochondrial ultrastructure with nanometer precision. This will enable a detailed analysis of local cristae organization and reveal inter- and intra-lysosomal heterogeneity in TRPML1 distribution, with a particular focus on mitochondria–lysosome interfaces.
Overall, this project offers an exciting opportunity for a student interested in single-cell biology, organelle dynamics, and cutting-edge microscopy to study how nanoscale ion signaling and organelle architecture jointly control cancer cell metabolism under energy stress.
References
1 Gottschalk, B; et al. 2024. Sci Rep 14, 14784 (2024). https://doi.org/10.1038/s41598-024-65595-z
2 Gottschalk, B; et al. 2022. Commun Biol.; 5(1): 649 Doi: 10.1038/s42003-022-03606-3.
3 Gottschalk, B; et al. 2019. Nat Commun.; 10(1):3732-3732 Doi: 10.1038/s41467-019-11692-x
4 Burgstaller, et al. 2019. ACS Sens.; 4(4): 883-891. Doi: 10.1021/acssensors.8b01599
People Involved
Primary supervisor: Benjamin Gottschalk