Involved in neuronal differentiation, including differentiation and migration of neuronal stem cells (By similarity). Plays a role in neuronal plasticity and is involved in neurite and filopodia outgrowth, filopodia motility and probably synapse formation. Gpm6a-induced filopodia formation involves mitogen-activated protein kinase (MAPK) and Src signaling pathways. May be involved in neuronal NGF-dependent Ca(2+) influx. May be involved in regulation of endocytosis and intracellular trafficking of G-protein-coupled receptors (GPCRs); enhances internalization and recycling of mu-type opioid receptor. Interacts with OPRM1 (PubMed:17548356). Interacts with palmitoyltransferase ZDHHC17/HIP14; the interaction leads to palmitoylation of GPM6A (By similarity). Localizes to cholesterol-rich lipid rafts of the plasma membrane of hippocampal neurons (PubMed:21426347). Localized to plasma membrane of cell bodies and neurites of hippocampal neurons (PubMed:16286650). Localized in membrane protrusions (filopodia and spines) of primary hippocampal neurons (PubMed:16286650). Localized to the growth cone edge membrane of elongating axons (By similarity). Expressed in hippocampus (at protein level). Isoform 1 is the predominant isoform expressed in brain, specifically in hippocampus. Isoform 2 is expressed at low levels in brain and kidney. Down-regulated by chronic stress in dentate gyrus granule neurons and CA3 pyramidal neurons. Up-regulated in the medial prefrontal cortex. N-glycosylated. Palmitoylated by ZDHHC17/HIP14. Belongs to the myelin proteolipid protein family.