Interactions of TOM1L1 with the multivesicular body sorting machinery.
Tom1L1 (Tom1-like1) and related proteins Tom1 (Target of Myb1) and Tom1L2 (Tom1-like2) constitute a new protein family characterized by the presence of a VHS (Vps27p/Hrs/Stam) domain in the N-terminal portion followed by a GAT (GGA and Tom) domain. Recently it was demonstrated that the GAT domain of both Tom1 and Tom1L1 binds ubiquitin, suggesting that these proteins might participate in the sorting of ubiquitinated proteins into multivesicular bodies (MVBs). Here we report a novel interaction between Tom1L1 and members of the MVB sorting machinery. Specifically, we found that the VHS domain of Tom1L1 interacts with Hrs (Hepatocyte growth factor-regulated tyrosine kinase substrate), whereas a PTAP motif, located between the VHS and GAT domain of Tom1L1, is responsible for binding to TSG101 (tumor susceptibility gene 101). Myc epitope-tagged Tom1L1 showed a cytosolic distribution but was recruited to endosomes following Hrs expression. In addition, Tom1L1 possesses several tyrosine motifs at the C-terminal region that mediate interactions with members of the Src family kinases and other signaling proteins such as Grb2 and p85. We showed that a fraction of Fyn kinase localizes at endosomes and that this distribution becomes more evident after epidermal growth factor internalization. Moreover, expression of a constitutive active form of Fyn also promoted the recruitment of Tom1L1 to enlarged endosomes. Taken together, we propose that Tom1L1 could act as an intermediary between signaling and degradative pathways.
Puertollano
Rosa
R
Laboratory of Cell Signaling, NHLBI, National Institutes of Health, Bethesda, Maryland 20892, USA. puertolr@mail.nih.gov
D056827:Endosomal Sorting Complexes Required for Transport; D049452:Green Fluorescent Proteins / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D010750:Phosphoproteins / Q000737:chemistry / Q000378:metabolism; D016133:Polymerase Chain Reaction; D011485:Protein Binding; D011506:Proteins / Q000737:chemistry / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D025801:Ubiquitin / Q000378:metabolism
D056827:Endosomal Sorting Complexes Required for Transport; D047908:Intracellular Signaling Peptides and Proteins; D010750:Phosphoproteins; D011506:Proteins; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; C120296:TOM1 protein, human; D025801:Ubiquitin; C096164:hepatocyte growth factor-regulated tyrosine kinase substrate; D049452:Green Fluorescent Proteins