A myosin-7B-dependent endocytosis pathway mediates cellular entry of ?-synuclein fibrils and polycation-bearing cargos.

ABSTRACT: Cell-to-cell transmission of misfolding-prone ?-synuclein (?-Syn) has emerged as a key pathological event in Parkinson's disease. This process is initiated when ?-Syn-bearing fibrils enter cells via clathrin-mediated endocytosis, but the underlying mechanisms are unclear. Using a CRISPR-mediated knockout screen, we identify SLC35B2 and myosin-7B (MYO7B) as critical endocytosis regulators for ?-Syn preformed fibrils (PFFs). We show that SLC35B2, as a key regulator of heparan sulfate proteoglycan (HSPG) biosynthesis, is essential for recruiting ?-Syn PFFs to the cell surface because this process is mediated by interactions between negatively charged sugar moieties of HSPGs and clustered K-T-K motifs in ?-Syn PFFs. By contrast, MYO7B regulates ?-Syn PFF cell entry by maintaining a plasma membrane-associated actin network that controls membrane dynamics. Without MYO7B or actin filaments, many clathrin-coated pits fail to be severed from the membrane, causing accumulation of large clathrin-containing "scars" on the cell surface. Intriguingly, the requirement for MYO7B in endocytosis is restricted to ?-Syn PFFs and other polycation-bearing cargos that enter cells via HSPGs. Thus, our study not only defines regulatory factors for ?-Syn PFF endocytosis, but also reveals a previously unknown endocytosis mechanism for HSPG-binding cargos in general, which requires forces generated by MYO7B and actin filaments.

SUBMITTER: Zhang Q 

PROVIDER: S-EPMC7245082 | biostudies-literature | 2020 May

REPOSITORIES: biostudies-literature