The role of unfolded protein deposits in cardiac dysfunction
Author(s)
Gianni, Davide
Type
Thesis
Abstract
In this study we investigated the role of unfolded proteins as a toxic insult for
cardiomyocytes in idiopathic dilated cardiomyopathy (DCM).
We first confirmed the presence of amyloid fibers in DCM cardiomyocytes by
histological and ultrastructural analysis, showing their preferentially intracellular
distribution. These molecular species seem to coexist with low-complexity β-folded
precursors (oligomers) which in our experiments could promote increase of systolic
Ca2+ in normal cardiomyocytes and alterations of contractility.
Our results suggest that these molecular species trigger the overexpression of UPR
components such as GRPs, Chop and Caspase 12. In addition we demonstrated the
presence of interactions between presenilins (PS) and Serca2a, suggesting a
regulatory role of these Alzheimer’s-related proteins on the Ca2+ pump. The genetic
analysis of the presenilin genes in DCM samples identified two undescribed
mutations in the promoter of PS1, which appeared to inhibit the expression of the
protein. The quantification of the presenilin levels showed a considerable decrease of
PS2 associated with an increase of PS1.
In order to characterize the protein(s) involved in the aggregasomes, we developed a
series of purification protocols, which, unfortunately, did not identify a single protein
species. As an alternative approach, we focused on the identification of transcripts
differentially expressed in iDCM. Our study introduces an innovative three-group
analysis in which we used amyloid samples to eliminate the interference related to the
accumulation of unfolded peptides and deriving from the progression of HF.
Interestingly we recognized a limited number of iDCM-specific genes, including
nestin and DSCR1, which are normally correlated to neural development.
In conclusion, our findings open intriguing perspectives to increase our knowledge of
the etiology and progression of DCM. However further investigation is required to
identify the protein(s) involved in the formation of the aggregasomes and the role of
these molecular structures in the etiology of the disease.
cardiomyocytes in idiopathic dilated cardiomyopathy (DCM).
We first confirmed the presence of amyloid fibers in DCM cardiomyocytes by
histological and ultrastructural analysis, showing their preferentially intracellular
distribution. These molecular species seem to coexist with low-complexity β-folded
precursors (oligomers) which in our experiments could promote increase of systolic
Ca2+ in normal cardiomyocytes and alterations of contractility.
Our results suggest that these molecular species trigger the overexpression of UPR
components such as GRPs, Chop and Caspase 12. In addition we demonstrated the
presence of interactions between presenilins (PS) and Serca2a, suggesting a
regulatory role of these Alzheimer’s-related proteins on the Ca2+ pump. The genetic
analysis of the presenilin genes in DCM samples identified two undescribed
mutations in the promoter of PS1, which appeared to inhibit the expression of the
protein. The quantification of the presenilin levels showed a considerable decrease of
PS2 associated with an increase of PS1.
In order to characterize the protein(s) involved in the aggregasomes, we developed a
series of purification protocols, which, unfortunately, did not identify a single protein
species. As an alternative approach, we focused on the identification of transcripts
differentially expressed in iDCM. Our study introduces an innovative three-group
analysis in which we used amyloid samples to eliminate the interference related to the
accumulation of unfolded peptides and deriving from the progression of HF.
Interestingly we recognized a limited number of iDCM-specific genes, including
nestin and DSCR1, which are normally correlated to neural development.
In conclusion, our findings open intriguing perspectives to increase our knowledge of
the etiology and progression of DCM. However further investigation is required to
identify the protein(s) involved in the formation of the aggregasomes and the role of
these molecular structures in the etiology of the disease.
Date Issued
2011
Date Awarded
2011-08
Copyright Statement
Attribution NoDerivatives 4.0 International Licence (CC BY-ND)
Advisor
Harding, Sian
Creator
Gianni, Davide
Publisher Department
Medicine: National Heart and Lung Institute
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)