Periodic Reporting for period 1 - LipLAge (Exploring lamin-lipid interactions and the loss of nuclear structural integrity as the molecular determinants of human aging)
Okres sprawozdawczy: 2021-09-01 do 2023-08-31
Aging acts as a major risk factor for many human pathologies, including cancer, neurodegenerative disorders, diabetes, and cardiovascular diseases. Over the years, the global trend has been for people to live longer, with projections for 2030 indicating that individuals aged 60 and older will surpass the youth population and double the number of children under five. This has prompted a strong interest in aging research in the past decades. Nonetheless, additional information on the determinants of biological deterioration is still required if we aim at providing a better quality of life for aging individuals, together with creative and efficient ways to counteract them and prevent age-prone diseases.
In the LipLAge project, the focus was to understand why human cell nuclei tend to lose structural integrity as age progresses, ultimately leading to functional impairment. We envisioned a new paradigm where the lipid composition of the nuclear envelope, and not only proteins and nucleic acids, would have an active role in regulating the overall integrity of the nucleus. More specifically, our strategy was to address the interplay between lamin proteins and the lipids of the nuclear envelope, and to understand how these interactions affect nuclear lamina architecture and nuclear structure during human aging. Overall, our results show that, as age progresses, there is a significant decrease in the content of ether lipids in the nucleus of human skin cells. Moreover, this difference in membrane composition results in altered membrane biophysical properties, ultimately leading to a differential binding of lamin proteins to the nuclear envelope.
In the LipLAge project, the focus was to understand why human cell nuclei tend to lose structural integrity as age progresses, ultimately leading to functional impairment. We envisioned a new paradigm where the lipid composition of the nuclear envelope, and not only proteins and nucleic acids, would have an active role in regulating the overall integrity of the nucleus. More specifically, our strategy was to address the interplay between lamin proteins and the lipids of the nuclear envelope, and to understand how these interactions affect nuclear lamina architecture and nuclear structure during human aging. Overall, our results show that, as age progresses, there is a significant decrease in the content of ether lipids in the nucleus of human skin cells. Moreover, this difference in membrane composition results in altered membrane biophysical properties, ultimately leading to a differential binding of lamin proteins to the nuclear envelope.
At the beginning of the project, we set out to detect any possible age-related differences in the lipid content of the nuclear envelope. To do that, we first procured primary skin cells from healthy donors of young (<13 yo) and old age (>67 yo), as well as Hutchinson-Gilford Progeria Syndrome patients (HGPS, a premature aging disease). Second, cell nuclei had to be properly isolated from the remaining cell components. For that, we developed and optimized a new detergent-free protocol based on cell sorting to collect fully isolated nuclei, that we extensively characterized using confocal microscopy, transmission electron microscopy and atomic force microscopy. Third, we evaluated and compared the lipidome of the 3 nuclei populations (young, old and HGPS) by hydrophilic interaction liquid chromatography (HILIC)-MS/MS. The lipidomics analysis showed a significant decrease in ether lipids within the nucleus as age progresses, with no gender variability being observed.
Since we did not know exactly how this change in ether lipid content would affect the biophysical properties of the membrane itself, we prepared membrane models containing different levels of this lipid class and characterize them using a set of fluorescence spectroscopy techniques, including time-dependent fluorescence shifts, generalized polarization, dynamic light scattering and fluorescence anisotropy. Our results show a decrease in membrane order (higher hydration) at the interface level with increasing ether lipid content, meaning that the nuclear envelope might be getting more rigid with age. To address lipid-lamin interactions in these models, we used an 18-amino acid peptide corresponding to the C-terminal of prelamin A. Confocal microscopy and fluorescence correlation spectroscopy data suggest that the extent of peptide binding to the models is in part influenced by the level of ether lipids in the membrane. Further studies with full-length lamins (that we are now purifying) will reveal whether the observed differences have an impact in lamin polymerization and lamin meshwork morphology.
Since we did not know exactly how this change in ether lipid content would affect the biophysical properties of the membrane itself, we prepared membrane models containing different levels of this lipid class and characterize them using a set of fluorescence spectroscopy techniques, including time-dependent fluorescence shifts, generalized polarization, dynamic light scattering and fluorescence anisotropy. Our results show a decrease in membrane order (higher hydration) at the interface level with increasing ether lipid content, meaning that the nuclear envelope might be getting more rigid with age. To address lipid-lamin interactions in these models, we used an 18-amino acid peptide corresponding to the C-terminal of prelamin A. Confocal microscopy and fluorescence correlation spectroscopy data suggest that the extent of peptide binding to the models is in part influenced by the level of ether lipids in the membrane. Further studies with full-length lamins (that we are now purifying) will reveal whether the observed differences have an impact in lamin polymerization and lamin meshwork morphology.
The implementation of the LipLAge project yielded new and exciting data that push our knowledge of nuclear envelope lipid biology beyond the state-of-the-art. Our results show a significant decrease in the content of ether lipids within the nucleus of human cells with age progression. Since plasmalogens (a sub-class of ether lipids) are natural antioxidants, this might contribute to a diminished ability of aged nuclei to keep structural integrity and thus being more susceptible to disease. Moreover, the amount of ether lipids at the nuclear envelope seem to contribute to differential binding of peptides resembling the C-terminal of lamin A, which might ultimately lead to polymerization alterations and overall loss of proper and healthy biomechanical properties. Downstream of this project, our results will contribute to design innovative strategies to counteract the aging of the nuclear envelope, thus delaying its negative impact and decreasing the propensity to age-prone diseases.