Proteoglycan playing a role in cell proliferation and migration which stimulates endothelial cells motility during microvascular morphogenesis. May also inhibit neurite outgrowth and growth cone collapse during axon regeneration. Cell surface receptor for collagen alpha 2(VI) which may confer cells ability to migrate on that substrate. Binds through its extracellular N-terminus growth factors, extracellular matrix proteases modulating their activity. May regulate MPP16-dependent degradation and invasion of type I collagen participating in melanoma cells invasion properties. May modulate the plasminogen system by enhancing plasminogen activation and inhibiting angiostatin. Functions also as a signal transducing protein by binding through its cytoplasmic C-terminus scaffolding and signaling proteins. May promote retraction fiber formation and cell polarization through Rho GTPase activation. May stimulate alpha-4, beta-1 integrin-mediated adhesion and spreading by recruiting and activating a signaling cascade through CDC42, ACK1 and BCAR1. May activate FAK and ERK1/ERK2 signaling cascades. Interacts with ITGA4 through its chondroitin sulfate glycosaminoglycan. Interacts with BCAR1, CDC42 and ACK1. Interacts with MMP16. Interacts with the first PDZ domain of MPDZ. Interacts with PRKCA. Interacts with LGALS3 and the integrin composed of ITGB1 and ITGA3. Binds TNC, laminin-1, COL5A1 and COL6A2. Interacts with PLG and angiostatin. Binds FGF2 and PDGFA (By similarity). Interacts with GRIP1, GRIP2 and GRIA2. Forms a ternary complex with GRIP1 and GRIA2. Localized at the apical plasma membrane it relocalizes to the lamellipodia of astrocytoma upon phosphorylation by PRKCA. Localizes to the retraction fibers. A fraction may undergo cell surface proteolysis and secretion (By similarity). Localizes to the plasma membrane of oligodendrocytes (PubMed:12458226). Expressed in microcascular pericytes and not endothelial cells. O-glycosylated; contains glycosaminoglycan chondroitin sulfate which are required for proper localization and function in stress fiber formation. Involved in interaction with MMP16 and ITGA4 (By similarity). Phosphorylation by PRKCA regulates its subcellular location and function in cell motility. Mice are unresponsive to PDGF-AA through PDGF-alpha receptor. Valuable marker for several incompletely differentiated precursor cells.