Orchid.org ID: orcid.org/0000-0002-1583-6092
LIPID DROPLET BIOLOGY
Molecular mechanisms in the pathogenesis of human lipodystrophies
Lipodystrophies are genetic or acquired human disorders characterized by a complete or partial lack of body fat. This malfunction in the formation of adipose tissue leads to the deposition of excess lipids in other body regions and organs. In addition, the the lack of adipose tissue often leads to severe metabolic complications such as insulin resistance, diabetes mellitus, hypertriglyceridemia and fatty liver, which also manifest in obese patients. Furthermore, lipodystrophy patients suffer from leptin deficiency, an important hormone that regulates the sensation of hunger and thus energy homeostasis. In case of genetically-induced lipodystrophies, further serious morphological and physiological abnormalities are observed, in particular in the skeletal and cardiac musculature but also in other body regions. Lipodystrophies are incurable. Therapeutic measures are applied mainly to alleviate metabolic complications. The detailed mechanisms of the pathogenesis of lipodystrophies are unknown. My research interest lies in the elucidation of the processes leading to the most severe form of lipodystrophy in humans, caused by mutations in the BSCL2 (‘seipin’) gene.
Seipin is involved in the regulation of phosphatidic acid homeostasis
Using the model organism yeast, we were able to mechanistically characterize processes leading to the formation of significant phenotypic alternations in Seipin mutants: phosphatidic acid (PA) is an important precursor molecule for the synthesis of phospholipids, the components of cellular membranes, as well as for the synthesis of neutral lipids stored in lipid droplets (LD). Our work provided strong evidence for a function of seipin as a scaffold for various enzymes involved in the synthesis and utilization of PA, such as yeast Pah1 ("phosphatidate phosphatase 1"; ortholog of human lipin-1). The malfunction of Seipin leads to a mislocalization of Pah1. As a consequence, the incorporation of PA into phospholipids and neutral lipids is imbalanced leading to a local increase of PA levels at the nuclear envelope. This phenomenon initiates a cascade of linked cellular processes: the abnormal local proliferation of LD-associated endoplasmic reticulum membranes at the nucleus, the clustering of associated LD, and ultimately the formation of extremely enlarged lipid droplets due to altered phospholipid composition (1).
In a future project, we will study the effects of altered PA homeostasis and phospholipid composition, as has also been observed in seipin deficient mammalian cells, on the transcriptional regulation and subcellular dynamics of enzymes pivotal for the formation of adipose tissue. In this respect, we aim at finding new targets for the therapeutic treatment of lipodystrophy patients.
Dynamics and interactions of subcellular structures - new method for 'superresolved' imaging and quantitative analysis of fluorescently labeled organelles and proteins developed
In this context, the spatial and time-resolved imaging of the dynamics of subcellular structures using live cell imaging is an important method to acquire complex time-dependent cellular processes in heterogeneous cell populations / tissues as suggested to be induced by seipin malfunction. In a previous study, using this methodology and high-end imaging, we were able to uncover the mode of growth and degradation of lipid droplets in adipocytes. This study demonstrated the power of time-resolved spatial imaging, especially for cell biology issues (2).
We have recently extended this approach, now allowing the "super"- and time-resolved simultaneous detection as well as quantification of fluorescently labeled proteins and organelles in living, multi-labeled mammalian cells. The extensive imaging informatics pipeline will be used to study the complex subcellular processes in seipin-deficient cells and beyond (3).
(1) H. Wolinski* (*corresponding author), H.F. Hofbauer, K. Hellauer, A. Cristobal-Sarramian, D. Kolb, M. Radulovic, O.L. Knittelfelder, G.N. Rechberger, S.D. Kohlwein (2015). Seipin is involved in the regulation of phosphatidic acid metabolism at a subdomain of the nuclear envelope in yeast. BBA Molecular and Cell Biology of Lipids 1851 (11):1450-1464.
(2) Paar, M., Jüngst, C., Steiner, N.A., Magnes, C., Sinner, F., Kolb, D., Lass, A., Zimmermann, R., Zumbusch, A., Kohlwein, S.D. & Wolinski, H*. (2012). Remodeling of lipid droplets during lipolysis and growth in adipocytes. Journal of Biological Chemistry, 287 (14), pp. 11164-11173.
Press release: https://steiermark.orf.at/news/stories/2521385/ (german).
(3) Pribasnig, M., Kien B., Pusch L., Haemmerle G., Zimmermann, R. & Wolinski H*. Extended-resolution confocal imaging of the interaction between lipid droplets and mitochondria. (2018). BBA Molecular and Cell Biology of Lipids, 1863(10):1285-1296.
Earlier works (selection):
Wolinski, H., Kolb, D., Hermann, S., Koning, R.I., Kohlwein, S.D. A role for seipin in lipid droplet dynamics and inheritance in yeast (2011) Journal of Cell Science, 124 (22), pp. 3894-3904.
Wolinski, H., Petrovic, U., Mattiazzi, M., Petschnlgg, J., Heise, B., Natter, K., Kohlwein, S.D. Imaging-based live cell yeast screen identifies novel factors involved in peroxisome assembly (2009) Journal of Proteome Research, 8 (1), pp. 20-27.
Wolinski, H., Kohlwein, S.D. Microscopic and spectroscopic techniques to investigate lipid droplet formation and turnover in yeast (2015) Methods in Molecular Biology, 1270, pp. 289-305.
Wolinski, H., Kohlwein, S.D. Single yeast cell imaging (2014) Methods in Molecular Biology, 1205, pp. 91-109.
Wolinski, H., Bredies, K., Kohlwein, S.D. Quantitative Imaging of Lipid Metabolism in Yeast: From 4D Analysis to High Content Screens of Mutant Libraries (2012) Methods in Cell Biology, 108, pp. 345-365.
Bredies*, K., Wolinski, H. An active-contour based algorithm for the automated segmentation of dense yeast populations on transmission microscopy images
(2011) Computing and Visualization in Science, 14 (7), pp. 341-352.
Wolinski, H., Natter, K., Kohlwein, S.D. The fidgety yeast: Focus on high-resolution live yeast cell microscopy (2009) Methods in Molecular Biology, 548, pp. 75-99.
Wolinski, H., Kohlwein, S.D. Microscopic analysis of lipid droplet metabolism and dynamics in yeast (2008) Methods in Molecular Biology, 457, pp. 151-163.
Cooperations - highlight:
Spribille T, Tuovinen V, Resl P, Vanderpool D, Wolinski H, Aime MC, Schneider K, Stabentheiner E, Toome-Heller M, Thor G, Mayrhofer H, Johannesson H, McCutcheon JP. Basidiomycete yeasts in the cortex of ascomycete macrolichens. 2016. Science. 29;353(6298):488-92.
The New York Times Article
Botany research papers:
Wolinski, H*. Confocal imaging reveals structural detail of the cell nucleus and ascospore formation in lichenized fungi (2003) Mycological Research, 107 (8), pp. 989-995.
Wolinski, H., Grube, M., Blanz, P. (1999). Direct PCR of symbiotic fungi using microslides(1999) BioTechniques, 26 (3), pp. 454-455.