The C-terminus of alpha-Synuclein regulates its dynamic cellular internalization by Neurexin 1 beta

Abstract

The aggregation of the disordered neuronal protein, -Synuclein (S), is the primary pathological feature of Parkinsons disease. Current hypotheses favor cell-to-cell spread of S species as underlying disease progression, driving interest in identifying the molecular and cellular species involved in cellular internalization of S. Prior work from our lab identified the chemically specific interaction between S and the pre-synaptic adhesion protein neurexin 1{beta} (N1{beta}) to be capable of driving cellular internalization of both monomer and aggregated forms of S. Here we explore the physical basis of N1{beta}-driven internalization of S. Specifically, we show that spontaneous internalization of S by SH-SY5Y and HEK293 cells expressing N1{beta} requires essentially all of the membrane-binding domain of S; S constructs truncated beyond residue 90 bind to N1{beta} in the plasma membrane of HEK cells, but are not internalized. Interestingly, prior to internalization, S and N1{beta} co-diffuse rapidly in the plasma membrane. S constructs that are not internalized show very slow mobility themselves, as well as slow N1{beta} diffusion. Finally, we find that truncated S is capable of blocking internalization of full-length S. Our results draw attention to the potential therapeutic value of blocking S-N1{beta} interactions.