HSPG2 and neuroblastoma: Since activation of opioid receptors has been shown to cause Gβγ-mediated ER Ca2+ release via PLC in neuroblastoma (Yoon et al., 1999) and leukocytes (Celik et al., 2016; Machelska and Celik, 2018), we tested the potential involvement of Gβγ in D,L-methadone-induced ER Ca2+ release in leukemic cells.