Fig 2: Knockdown of TPCs induces Treg proliferation.(A to E) WT mice were intraperitoneally injected with TPC siRNAs or nontargeting control for 2 days, and 24 hours later, tmTNF expression on splenic CD11c+ cells (A), proportion and number of splenic Tregs (B and C), and expression of Ki-67 (D) or TNFR2 (E) by Tregs were analyzed by FCM. (F to K) Two types of gene KO mice, including TNFR1 (F to H) or TNFR2 KO mice (I to K), were intraperitoneally injected with TPC siRNAs for 2 days. tmTNF expression on splenic CD11c+ cells (F and I) and proportion and number of Tregs in the spleen (G, H, J, and K) were analyzed by FCM. (L and M) WT mice were intraperitoneally injected with lentivirus encoding Tpcn1 or Tpcn2 or control. Twenty-four hours later, mice were treated with tetrandrine for 3 days. The proportion of Tregs in splenic CD4 cells (L) and the number of splenic Tregs (M) were analyzed by FCM. For typical FCM plots, the number indicated proportion of gated cells. Data (means ± SEM, n = 3 mice) were representative of three separate experiments. Compared with the indicated group, *P < 0.05, **P < 0.01, and ***P < 0.001; n.s., no significant differences.

Fig 3: TPC2 knockdown attenuates Tat endolysosome escape. A, Quantitative immunoblotting data showed that the expression of TPC2 was knocked down with specific shRNAs in H1299 cells (n = 3; **P < .01). B, Knockdown of TPC2 significantly attenuated Tat endolysosome escape in the absence of chloroquine (n = 3; *P < .05). Blocking TPCs with Ned-19 decreased Tat endolysosome escape in control shRNA-treated cells but did not further decrease Tat endolysosome escape in TPC2 knockdown cells (n = 3; *P < .05). C, TPC2 knockdown significantly enhanced the internalization of Tat-FITC (n = 4, *P < .05, ***P < .001, bar = 10 µm). D, Quantitative immunoblotting data showed that the expression of TRPML1 was knocked down with specific shRNAs in H1299 cells (n = 3; **P < .01). E, Knockdown of TRPML1 did not affect Tat endolysosome escape (n = 3; P > .05)

Fig 4: In vitro treatment with TPC inhibitors up-regulates tmTNF expression on APCs.(A to E) Raw264.7 cells, DC2.4 cells, mouse BMDCs, or human MoDCs were treated with 1 µM tetrandrine. After 48 hours, tmTNF expression was analyzed by FCM (A and B) or by Western blot (C) [total TNF in (E), Raw264.7 cell lysate]. Supernatant TNF levels were determined by enzyme-linked immunosorbent assay (ELISA) (D). MFI, mean fluorescence intensity. (F to H) BMDCs were treated with 100 µM diltiazem (DIL), nimodipine (NIM), verapamil (VER), or Ned 19 (NED) for 48 hours. tmTNF expression was analyzed by FCM (F and G). Supernatant TNF levels were determined by ELISA (H). (I to K) Mouse DC2.4 cells were transfected with TPCN1-specific (I and J) and TPCN2-specific (I and K) siRNA. After 48 hours, tmTNF was analyzed by FCM. Data were presented as means ± SEM (n = 3 to 6 independent experiments). By comparison with vehicle control group, *P < 0.05, **P < 0.01, and ***P < 0.001; n.s., no significant differences.

Fig 5: Two-pore channels (TPCs) mediate NAADP-induced lysosomal Ca2+ release in C-MSCs. (A) TPC1 and TPC2 gene expression in total RNA extracts of C-MSCs. qRT-PCR data are shown as transcript abundance (genes threshold cycles [Ct] with respect to the house-keeping gene GAPDH). n = 4/group. Student’s t-test: ***p < 0.001. (B) Western Blot analysis of TPC1 and TPC2 proteins in total cellular extracts. n = 3/group. (C) The Ca2+ response to NAADP-AM was suppressed by incubating the cells with the following TPC inhibitors: NED-19 (100 µM, 30 min), NED-K (10 µM, 30 min), and tetrandrine (10 µM, 30 min). (D) Mean ± SE of the amplitude of the peak Ca2+ response to NAADP in the absence (Ctrl) and in the presence of NED-19, NED-K and tetrandrine (Tetra). Student’s t-test: ***p < 0.001.