Sequestration of latent TGF-β binding protein 1 into CADASIL-related Notch3-ECD deposits.

Abstract : Introduction:Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy(CADASIL) represents the most common hereditary form of cerebral small vessel disease characterized by early-onsetstroke and premature dementia. It is caused by mutations in the transmembrane receptor Notch3, which promote theaggregation and accumulation of the Notch3 extracellular domain (Notch3-ECD) within blood vessel walls. This processis believed to mediate the abnormal recruitment and dysregulation of additional factors including extracellular matrix(ECM) proteins resulting in brain vessel dysfunction. Based on recent evidence indicating a role for the transforminggrowth factor-β(TGF-β) pathway in sporadic and familial small vessel disease we studied fibronectin, fibrillin-1 andlatent TGF-βbinding protein 1 (LTBP-1), three ECM constituents involved in the regulation of TGF-βbioavailability, inpost-mortembrain tissue from CADASIL patients and control subjects.Results:Fibronectin and fibrillin-1 were found to be enriched in CADASIL vessels without co-localizing with Notch3-ECDdeposits, likely as a result of fibrotic processes secondary to aggregate formation. In contrast, LTBP-1 showed both anaccumulation and a striking co-localization with Notch3-ECD deposits suggesting specific recruitment into aggregates.We also detected increased levels of the TGF-βprodomain (also known as latency-associated peptide, LAP) indicatingdysregulation of the TGF-βpathway in CADASIL development.In vitroanalyses revealed a direct interaction betweenLTBP-1 and Notch3-ECD and demonstrated a specific co-aggregation of LTBP-1 with mutant Notch3.Conclusion:We propose LTBP-1 as a novel component of Notch3-ECD deposits and suggest its involvement inpathological processes triggered by Notch3-ECD aggregation.