Positively regulates SLC1A1/EAAC1-mediated glutamate transport by increasing its affinity for glutamate in a PKC activity-dependent manner. Promotes the catalytic efficiency of SLC1A1/EAAC1 probably by reducing its interaction with ARL6IP5, a negative regulator of SLC1A1/EAAC1-mediated glutamate transport (By similarity). Plays a role in the formation and stabilization of endoplasmic reticulum tubules (PubMed:24262037). Negatively regulates apoptosis, possibly by modulating the activity of caspase-9 (CASP9). Inhibits cleavage of CASP9-dependent substrates and downstream markers of apoptosis but not CASP9 itself (PubMed:12754298). May be involved in protein transport, membrane trafficking, or cell signaling during hematopoietic maturation (PubMed:10995579). Homooligomer (PubMed:24262037). Heterodimer with ARL6IP5. Interacts with ARL6 (By similarity). Interacts with TMEM33 (PubMed:25612671). Interacts with ATL1 (PubMed:24262037). Predominantly localized to intracytoplasmic membranes. Preferentially localizes at the ER tubules and the edge of the ER sheets, both of which are characterized by a high membrane curvature. Expressed in all hematopoietic cell lineages, but the highest level of expression is found in early myeloid progenitor cells. Expressed in brain, bone marrow, thymus and lung. Expressed at low level in liver, kidney and spleen. Not detected in heart. Down-regulated during myeloid differentiation. Down-regulated by apoptotic stimuli. The transmembrane domains are required for its ability to shape the endoplasmic reticulum membrane into tubules. The disease is caused by variants affecting the gene represented in this entry. Belongs to the ARL6ip family. Truncated N-terminus.