The Impact of Inner Nuclear Membrane Protein Accumulation on Cellular Aging Phenotypes
Date
2023-05-02
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
Type
Thesis
Degree Level
Masters
Abstract
The premature aging disease Hutchinson-Gilford Progeria Syndrome (HGPS) is widely
accepted as a model of the aging process. Both HGPS patients and aged non-diseased individuals
have similar phenotypes at the organismal and cellular levels. One such phenotype is the abnormal
formation of the nuclear lamina, one of the components of the nuclear envelope. It has also been
observed that SUN1, an integral inner nuclear membrane protein, is present at higher levels in
HGPS patients. It is theorized that the major cause of abnormal nuclear morphology in HGPS is
the accumulation of progerin, a mutant of the primary protein component of the nuclear lamina
(lamin A). It has also been suggested that the accumulation of SUN1 is a causative factor and that
reducing levels of SUN1 reverses some of the cellular phenotypes of HGPS. To test if SUN1 levels
increase in HGPS and play a causative role in HGPS phenotypes, I performed Western blots for
SUN1 in 3 normal (non-diseased) primary human fibroblast cell lines and compared them to SUN1
levels in 3 cell lines cultured from HGPS patients. In my assays and experiments there was no
indication of increased levels of SUN1 in the HGPS cells examined. SUN1 was overexpressed by
stable transfection in osteosarcoma and primary human fibroblast cell lines and the nuclear
morphology of these cells was examined by immunofluorescence microscopy. The results did not
support the hypothesis that increased SUN1 levels would increase the number of cells exhibiting
abnormal nuclear morphology. The introduction of lamin A/C-∆50 (∆50), a progerin analogue,
into the same fibroblast and osteosarcoma cell lines gave contradicting results for increased levels
of SUN1. Western blot indicated no increase in SUN1 levels in the presence of exogenous progerin
compared to the empty vector control. However, quantification of SUN1 levels by
immunofluorescence did indicate an increase compared to the same controls. Together, these data
demonstrate that SUN1 accumulation alone does not cause abnormal lamina formation in the aging
process.
Description
Keywords
aging, nuclear lamina, protein accumulation
Citation
Degree
Master of Science (M.Sc.)
Department
Biochemistry
Program
Biochemistry