Component of a complex required to localize phosphatidylinositol 4-kinase (PI4K) to the plasma membrane (PubMed:23229899, PubMed:24417819). The complex acts as a regulator of phosphatidylinositol 4-phosphate (PtdIns(4)P) synthesis (Probable). In the complex, plays a central role in bridging PI4KA to EFR3B and FAM126A, via direct interactions (By similarity). Component of a phosphatidylinositol 4-kinase (PI4K) complex, composed of PI4KA, EFR3 (EFR3A or EFR3B), TTC7 (TTC7A or TTC7B) and FAM126 (FAM126A or FAM126B) (PubMed:24417819). Interacts with PI4KA (PubMed:34415310). Interaction with PI4KA is direct (By similarity). Interacts with EFR3 (EFR3A or EFR3B), interaction is direct (By similarity). Interacts with FAM126 (FAM126A or FAM126B), interaction is direct (By similarity). Association with the PI4K complex is strongly reduced by TMEM150A (By similarity). Localizes to the cytosol and is recruited to the plasma membrane following interaction with EFR3 (EFR3A or EFR3B). Expressed in epithelial cells of the intestine, thymus, and pancreas (at protein level). The disease is caused by variants affecting the gene represented in this entry. Phenotypic variations have been observed: the mildest case show intestinal aberrations consisting of bloody diarrhea, apoptotic enterocolitis, and acute graft-versus-host disease- (GVHD)-like symptoms, but no atresias (PubMed:25546680). Other patients show multiple intestinal atresias, some being associated with immunodeficiency syndrome, while other do not show immunodeficiency defects (PubMed:23423984). May be produced at very low levels due to a premature stop codon in the mRNA, leading to nonsense-mediated mRNA decay. Wrong choice of CDS.