Toni I (target of Myb 1) and its related proteins (Tom I L1/Srcasm and Toni I L2) constitute a protein family and share an N-terminal VHS (Vps27p/Hrs/Stam) domain and a following GAT (GGA and Tom1) domain, both of which are also conserved in the GGA family proteins. However, the C-terminal half is not significantly conserved between the Tom I and GGA families or even between Toni I and Toni I L1. We have previously shown that the GAT domain of Toni I interacts with Tollip (Toll-interacting protein), which is associated with endosomes, to which it recruits Tom1. We here extend the previous data and show that the GAT domains of Tom I L I and Tom I L2 also interact with Tollip, and the C-terminal regions of all the Tom I family proteins interact with clathrin. Furthermore, when coexpressed with Tollip, all the Toni I family proteins recruite clathrin onto endosomes. These results indicate that, in conjunction with Tollip, Tom1 family proteins play an important role in recruiting clathrin onto endosomes and suggest that they modulate endosomal functions. (c) 2006 Elsevier Inc. All rights reserved.