Fig. 4
From: The role of phosphatidylserine on the membrane in immunity and blood coagulation
The structure of TIM and the binding to PtdSer. The structure of TIM family. In mice, there are TIM-1, TIM-2, TIM-3, TIM-4, but TIM-2 does not interact with PtdSer. In humans, there are only TIM-1, TIM-3, TIM-4 [8]. Only TIM-4 has an RGD motif in the IgV-like domain and lacks a tyrosine phosphorylation motif in the cytoplasmic tail. The RGD motif in TIM-4 is the ligand of integrins [35] and the hallmark for adhesive proteins [36,37,38,39]. The model of TIM-1 and TIM-4 interacting PtdSer. TIM-1 and TIM-4 molecules can interact with the PtdSer on the exosome to form a bridge [40]. (2) TIM-1 or TIM-4 can directly interact with PtdSer on apoptotic cells [39]. The model of TIM-3 interacting PtdSer. TIM-3 may interact with PtdSer on exosomes. Galectin-9 can also link TIM-3 to N-linked glycan on another protein [8]. (2) TIM-3 can directly interact with PtdSer on apoptotic cells [38]. (3) Two TIM-3 molecules can be cross-linked by Galectin-9 [41, 42]