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Kast, Jessica (2014): Involvement of latent TGF-beta binding protein 1 in CADASIL-relevant Notch3 aggregation. Dissertation, LMU München: Faculty of Chemistry and Pharmacy



CADASIL (cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy) represents the most prevalent hereditary form of cerebral small vessel disease (SVD) resulting in early-onset stroke and vascular dementia. It is caused by stereotyped missense mutations in the transmembrane receptor Notch3, which alter the number of cysteine residues in the extracellular domain (ECD). This leads to the abnormal multimerization and extracellular deposition of mutant Notch3-ECD at the plasma membrane of smooth muscle cells in small blood vessels. Notch3-ECD-containing aggregates are the earliest manifestation of the disease and excess Notch3-ECD is believed to recruit functionally important extracellular matrix proteins resulting in brain vessel dysfunction. Biochemical and histological approaches on post-mortem brain tissue from CADASIL patients and control subjects as well as in vitro assays were used to study the consequences of Notch3-ECD deposition on the ECM components thrombospondin-2, fibrillin-1 and fibronectin and members of the latent transforming growth factor-β (TGF-β) binding protein (LTBP) family. It is demonstrated that the structural matrix components fibrillin-1 and fibronectin are enriched and contribute to the prominent thickening of CADASIL vessel walls without co-localizing with Notch3-ECD deposits, likely as a result of fibrotic adaptation secondary to aggregate formation. For LTBP-1, a key regulator of the TGF-β signaling pathway, an accumulation as well as a striking co-localization with Notch3-ECD deposits is shown suggesting specific recruitment into aggregates. Furthermore, increased levels of the TGF-β pro-domain (also known as latency-associated peptide, LAP) were found implying dysregulation of the TGF-β pathway in CADASIL development. Finally, a direct interaction of LTBP-1 with Notch3-ECD is demonstrated and evidence for a co aggregation with mutant Notch3 in vitro is provided. Conclusively, I propose LTBP-1 as a novel component of Notch3 deposits with a role in CADASIL pathogenesis.