Clathrin is not required for SNX-BAR-retromer mediated carrier formation

Clathrin has been implicated in retromer-mediated trafficking, but its precise function remains elusive. Given the importance of retromers for efficient endosomal sorting, we have sought to clarify the relationship between clathrin and the SNX-BAR-retromer. We find that the retromer SNX-BARs do not interact directly or indirectly with clathrin. In addition, we observe that SNX-BAR-retromer tubules and carriers are not clathrin-coated. Furthermore, perturbing clathrin function, by overexpressing a dominant negative clathrin or through suppression of clathrin expression, has no detectable affect on the frequency of SNX-BAR-retromer tubulation. We propose that SNX-BAR-retromer mediated membrane deformation and carrier formation does not require clathrin, and hence the role of clathrin in SNX-BAR-retromer function would appear to lie in pre-SNX-BAR-retromer cargo sorting.