English: Model of the retromer heterotrimer consisting of VPS26 (dark green), VPS35 (light orange) and VPS29 (red), which form a polymeric network of arches that wraps around the outer (cytoplasmic) side of the tubule. Inside the tubule, the large ectodomain of SORL1 forms a supporting polymeric network by dimerizing via two distinct interfaces. The two networks are connected through the transmembrane domain of SORL1 and its short C-terminal tail; the tail binds to VPS26(A or B) on the outside of the tubule. SORL1 thus not only serves as a cargo receptor; it is also an internal part of the retromer assembly, and helps to stabilize the self-association of retromer. The data used to construct this model came from the cryoET structure of retromer on the membrane, determined in Prof. Brett Collins' lab, and the model of the ectodomain of SORL1, constructed in Prof. Greg Petsko's lab by Dr. Yu Kitago. The proposed mode of dimerization of SORL1 is based on experimental work by Dr. Kitago and Prof. Olav Andersen, and is described in Jensen et al., PNAS (2023).}