Loss of INPP5K attenuates IP3-induced Ca2+ responses in the glioblastoma cell line U-251 MG cells

•The phosphoinositide 5-phosphatase NPPP5K resides at the endoplasmic reticulum (ER).•The impact of INPP5K function on ER Ca2+ dynamics in U-251 glioblastoma cells was examined.•Loss of INPP5K dampens IP3 receptor-mediated Ca2+fluxes in intact and permeabilized cells.•Loss of INPP5K did neither affect ER Ca2+-store content nor store-operated Ca2+ entry.•The mechanisms by which INPP5K controls IP3 receptor function requires further study.