Contribution of syndecans to cellular internalization and fibrillation of amyloid-β (1–42)

Letoha, Tamás and Hudák, Anett and Kusz, Erzsébet and Pettkó-Szandtner, Aladár and Racskóné Domonkos, Ildikó and Jósvay, Katalin and Szilák, László (2019) Contribution of syndecans to cellular internalization and fibrillation of amyloid-β (1–42). SCIENTIFIC REPORTS, 9 (1). ISSN 2045-2322

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Abstract

Intraneuronal accumulation of amyloid-beta(1-42) (A beta 1-42) is one of the earliest signs of Alzheimer's disease (AD). Cell surface heparan sulfate proteoglycans (HSPGs) have profound influence on the cellular uptake of A beta 1-42 by mediating its attachment and subsequent internalization into the cells. Colocalization of amyloid plaques with members of the syndecan family of HSPGs, along with the increased expression of syndecan-3 and -4 have already been reported in postmortem AD brains. Considering the growing evidence on the involvement of syndecans in the pathogenesis of AD, we analyzed the contribution of syndecans to cellular uptake and fibrillation of A beta 1-42. Among syndecans, the neuron specific syndecan-3 isoform increased cellular uptake of A beta 1-42 the most. Kinetics of A beta 1-42 uptake also proved to be fairly different among SDC family members: syndecan-3 increased A beta 1-42 uptake from the earliest time points, while other syndecans facilitated A beta 1-42 internalization at a slower pace. Internalized A beta 1-42 colocalized with syndecans and flotillins, highlighting the role of lipid-rafts in syndecan-mediated uptake. Syndecan-3 and 4 also triggered fibrillation of A beta 1-42, further emphasizing the pathophysiological relevance of syndecans in plaque formation. Overall our data highlight syndecans, especially the neuron-specific syndecan-3 isoform, as important players in amyloid pathology and show that syndecans, regardless of cell type, facilitate key molecular events in neurodegeneration.

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