a and b Lrmp interacted with IP3R proteins, including ITPR2, as determined by co-IP followed by LC-MS/MS assays in MEFs. a Lrmp-interacting proteins (label with red) mapped in “Chemo-sensing pathway” in KEGG. b Counts of Lrmp and IP3Rs detected by co-IP followed by LC-MS/MS assays in MEFs. c Lrmp-ITPR2 interaction was confirmed by co-IP assays followed by Western-blot assays in MEFs transfected with vectors expressing Lrmp-Flag and ITPR2-HA, respectively. d The binding region of Lrmp for ITPR2 was determined by co-IP followed by Western-blot assays in H1299 cells transfected with vectors expressing different Lrmp-Flag fragments and ITPR2-HA, respectively. Upper panel: schematic representation of vectors expressing full-length (FL) or serial deletion mutants of Lrmp-Flag. e The Lrmp-IPTR2 interaction was examined by PLA assays in WT and Lrmp−/− small intestinal tissues. Red: PLA signals of the Lrmp-ITPR2 interaction; green: Dclk1; DAPI: nucleus. f–h Ca2+ flux in response to Ionomycin (2 µM) treatment in WT, p53−/− and Lrmp−/− MEFs with or without transfection of either FL- or ΔM-Lrmp-Flag vectors. f Average traces of Ca2+ responses. g Relative Fluo-4 fluorescence obtained from Ca2+ transients at peak (48 s). h Representative fluorescence images. The Fluo-4 fluorescence intensity before Ionomycin treatment was calculated as 1. In f, each curve represents an average of at least 90 cells. Curves of each cell are shown in Fig S7. ***p < 0.001; **p < 0.01; NS: non-significant, two-tailed Student’s t-test.