Facilitative glucose transporter, which is responsible for constitutive or basal glucose uptake (PubMed:2211693). Has a very broad substrate specificity; can transport a wide range of aldoses including both pentoses and hexoses (By similarity). Most important energy carrier of the brain: present at the blood-brain barrier and assures the energy-independent, facilitative transport of glucose into the brain (By similarity). In association with BSG and NXNL1, promotes retinal cone survival by increasing glucose uptake into photoreceptors (By similarity). D-glucose(out) = D-glucose(in) The uptake of glucose is inhibited by cytochalasin B. Glucose uptake is increased in response to phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) treatment: TPA-induced glucose uptake requires phosphorylation at Ser-226. Found in a complex with ADD2, DMTN and SLC2A1. Interacts (via C-terminus cytoplasmic region) with DMTN. Interacts with SNX27; the interaction is required when endocytosed to prevent degradation in lysosomes and promote recycling to the plasma membrane. Interacts with STOM (By similarity). Interacts with GIPC (via PDZ domain) (PubMed:10198040). Interacts with SGTA (via Gln-rich region) (PubMed:15708368). Interacts with isoform 1 of BSG (By similarity). Detected in osteoblastic cells (at protein level). Detected in brain, and at lower levels in kidney, heart and lung. Phosphorylation at Ser-226 by PKC promotes glucose uptake by increasing cell membrane localization. Belongs to the major facilitator superfamily. Sugar transporter (TC 2.A.1.1) family. Glucose transporter subfamily.