Anchors the extracellular matrix to the cytoskeleton via F-actin. Ligand for dystroglycan. Component of the dystrophin-associated glycoprotein complex which accumulates at the neuromuscular junction (NMJ) and at a variety of synapses in the peripheral and central nervous systems and has a structural function in stabilizing the sarcolemma. Also implicated in signaling events and synaptic transmission. Interacts with SYNM (By similarity). Interacts with the syntrophins SNTG1 and SNTG2. Interacts with KRT19. Component of the dystrophin-associated glycoprotein complex which is composed of three subcomplexes: a cytoplasmic complex comprised of DMD (or UTRN), DTNA and a number of syntrophins, such as SNTB1, SNTB2, SNTG1 and SNTG2, the transmembrane dystroglycan complex, and the sarcoglycan-sarcospan complex. Interacts with DAG1 (betaDAG1) with DMD; the interaction is inhibited by phosphorylation on the PPXY motif of DAG1 (By similarity). Interacts with SYNM; SNTA1 and SNTB1. Interacts with CMYA5. Directly interacts with ANK2 and ANK3; these interactions do not interfere with betaDAG1-binding and are necessary for proper localization in muscle cells. Identified in a dystroglycan complex that contains at least PRX, DRP2, UTRN, DMD and DAG1 (By similarity). Interacts with DTNB (By similarity). Interacts with PGM5; the interaction is direct (By similarity). In muscle cells, sarcolemma localization requires the presence of ANK2, while localization to costameres requires the presence of ANK3. Localizes to neuromuscular junctions (NMJs). In adult muscle, NMJ localization depends upon ANK2 presence, but not in newborn animals. In the retina, expressed in the outer plexiform layer (OPL) and around the blood vessels. Also observed at the vitreal border of the retina corresponding to the inner limiting membrane (ILM). Presynaptically localized in cone pedicles and postsynaptically in bipolar cells (at protein level).