HSPG2 and astrocytoma (excluding glioblastoma): In fact, P2Y1 receptors, are coupled to G(q) proteins and mediate astroglial proliferation through activation of phospholipase (PLC)-protein kinase C (PKC)-extracellular signal-regulated kinase 1/2 (ERK1/2) pathway (Neary et al., 2003; Quintas et al., 2011a), whereas P2Y12 receptor activation may lead to G(i) βγ-dependent PLC-PKC-ERK1/2 pathway, as seen in 1321N1 human astrocytoma cells (Mamedova et al., 2006) or to a PLC-independent activation of PKC, as seems to occur in glioma C6 cells (Grobben et al., 2001; Van Kolen and Slegers, 2006).