Thomas Simmen

Research

Membrane Contact Sites between the endoplasmic reticulum (ER) and mitochondria as determinants in cancer and neurodegeneration

Current biomedical research aims to understand how we can pharmacologically halt the progression of a variety of chronic diseases that are associated with aging or genetic mutations. Prominent examples are cancer and neurodegeneration, where the cellular lifespan is either abnormally extended (cancer) or shortened (neurodegeneration). Other examples include muscular dystrophy and diabetes. Frequently, it is thought that a major cause for such diseases lies in the alteration of cellular metabolism that would compromise the proper functioning and survival of cells.

Our laboratory works to understand how such changes occur and how we can manipulate them. To do so, we focus on intracellular contact sites between two organelles: the endoplasmic reticulum (ER) and mitochondria. On these contact sites, the two organelles exchange Ca²⁺ ions. This ion flux controls the progression of the Krebs cycle inside mitochondria and can trigger the release of pro-apoptotic proteins from mitochondria. Therefore, the extent by which the ER and mitochondria interact with each other determines cellular energy production and cellular death.

In multiple publications from the lab, we have shown that when contacts between the ER and mitochondria are not formed properly, imbalances of cellular metabolism and abnormal cellular lifespan result. We have detected the same changes in specimens from human patients that suffer from cancer and multiple sclerosis (MS). In ongoing research, we now characterize further mechanisms associated with defects of ER-mitochondria contacts and how they malfunction in disease.

Candidates for undergraduate research (Cell 398, 498, 499), for summer studentships, for graduate studies or for postdoctoral fellowships are invited to contact the Principal Investigator at thomas.simmen@ualberta.ca.

 

Measuring the extent of ER-Mitochondria contact formation via electron microscopy. The knockdown of the TMX1 protein reduces contacts (see reference 2 Raturi et al., 2016).

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Selected Publications

1. Herrera-Cruz MS, Yap MC, Tahbaz N, Phillips K, Thomas L, Thomas G,and Simmen T. Rab32 uses its effector reticulon 3L to trigger autophagic degradation of mitochondria-associated membrane (MAM) proteins. Biol Direct. 2021 Nov 7;16(1):22.

2. Yousuf MS, Samtleben S, Lamothe SM, Friedman TN, Catuneanu A, Thorburn K, Desai M, Tenorio G, Schenk GJ, Ballanyi K, Kurata HT,Simmen T, and Kerr BJ. (2020) Endoplasmic reticulum stress in the dorsal root ganglia regulates large-conductance potassium channels and contributes to pain in a model of multiple sclerosis. FASEB J. 2020 Jul 17. doi: 10.1096/fj.202001163R.

3. Gutiérrez, T., Qi, H., Yap, M.C., Tahbaz, N., Milburn, L.A., Lucchinetti, E., Lou, P.H., Zaugg, M., LaPointe, P.G., Mercier, P., Overduin, M., Bischof, H., Burgstaller, S., Malli, R., Ballanyi, K., Shuai, J.,and Simmen T. (2020) The ER chaperone calnexin controls mitochondrial positioning and respiration. Sci Signal. 2020 Jun 30;13(638):eaax6660. doi: 10.1126/scisignal.aax6660.

4. Scorrano L, De Matteis MA, Emr S, Giordano F, Hajnóczky G, Kornmann B, Lackner LL, Levine TP, Pellegrini L, Reinisch K, Rizzuto R, Simmen T, Stenmark H, Ungermann C, and Schuldiner M. (2019) Coming together to define membrane contact sites. Nat Commun. 2019 Mar 20;10(1):1287. doi: 10.1038/s41467-019-09253-3.

5. Yoboue, E.D., Sitia, R., and Simmen, T. (2018) Redox crosstalk at mitochondria-associated membranes (MAMs) uses toxic waste to deliver messages. Cell Death and Disease. 28; 9 (3): 331.

6. Haile, Y., Deng, X., Ortiz-Sandoval, C., Tahbaz, N., Janowicz, A., Lu, J. Q., Kerr, B. J., Gutowski, N. J., Holley, J. E., Eggleton, P., Giuliani, F.,Simmen, T. (2017) Rab32 connects ER stress to mitochondrial defects in multiple sclerosis. Journal of Neuroinflammation. 23;14(1):19.

7. Raturi, A., Gutiérrez, T., Ortiz-Sandoval, C., Ruangkittisakul, A., Herrera-Cruz, M. S., Rockley, J. P., Gesson, K., Ourdev, D., Lou, P. H., Lucchinetti, E., Tahbaz, N., Zaugg, M., Baksh, S., Ballanyi, K.,and Simmen, T. (2016) TMX1 determines cancer cell metabolism as a thiol-based modulator of ER-mitochondria Ca2+ flux. Journal of Cell Biology. 214(4):433-44.

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Laboratory Members

Graduate Students
Junsheng Chen
Lucas Mina

Technician
Megan Yap