FIGURE 1.

Phosphatidylinositols transfer proteins. (A) PI-transfer proteins. The five human PI-transfer proteins can be divided into small proteins consisting of a single PI-transfer domain (PITD) including PITPα/β and PITPNC1, and the multi-domains containing proteins Nir2 and Nir3. Shown are the PITD, the FFAT motif, DDHD, and the C-terminal LNS2 (Lipin/Nde1/Smp2) domain. Glycine rich region is found only in Nir3 (Lev, 2004). PITPNC1 phosphorylation sites (S274 and S299), which bind 14-3-3, are represented as red dots on PITPNC1 protein (Halberg et al., 2016). (B) TIPE3, a PIP₂, and PIP₃ transfer protein. TIPE is the only protein that is known to transfer phosphoinositides. It preferentially binds PIP₂ and PIP₃, and contributes to increase their levels at the PM by mediating efficient supply of PIP₂ and presenting it to PI3K to produce PIP₃ (Fayngerts et al., 2014). The numbers at the right side of each protein indicate the length of each protein in amino acids.