T-cell-receptor signalling in inositol 1,4,5-trisphosphate receptor (IP3R) type-1-deficient mice: is IP3R type 1 essential for T-cell-receptor signalling?
Stimulation of T-cells via the T-cell receptor (TCR) complex is accompanied by an increase in intracellular Ca2+ concentration ([Ca2+]i). Recently, it was reported that a stable transformant of the human T-cell line, Jurkat, expressing an antisense cDNA construct of inositol 1,4,5-trisphosphate receptor (IP3R) type 1 (IP3R1), failed to demonstrate increased [Ca2+]i or interleukin-2 production after TCR stimulation and was also resistant to apoptotic stimuli. This cell line lacked IP3R1 expression, but expressed the type-2 and -3 receptors, IP3R2 and IP3R3 respectively [Jayaraman, Ondriasova, Ondrias, Harnick and Marks (1995) Proc. Natl. Acad. Sci. U.S.A. 92, 6007-6011, and Jayaraman and Marks (1997) Mol. Cell. Biol. 17, 3005-3012]. The authors concluded that IP3R1 is essential for TCR signalling and suggested that Ca2+ release via IP3R1 is a critical mediator of apoptosis. To establish whether a loss of IP3R1 function in T-cells occurred in vivo and in vitro, we investigated Ca2+ signalling after TCR stimulation and the properties of T-cells using IP3R1-deficient (IP3R1-/-) mice. As IP3R1-/- mice die at weaning, we transplanted bone marrow cells of IP3R1-/- mice into irradiated wild-type mice. Western blot analysis showed that the recipient IP3R1-containing (IP3R1+/+) lymphocytes were replaced by the donor IP3R1-/- lymphocytes after transplantation and that expression of IP3R2 and IP3R3 was unaltered. In contrast with the previous reports, T-cells lacking IP3R1 were able to mobilize Ca2+ from intracellular Ca2+ stores after stimulation via the TCR. We observed no significant differences between IP3R1+/+ and IP3R1-/- T-cells in terms of the number of thymocytes and splenocytes, the proportion of the T-cell phenotype, proliferative response to anti-CD3 monoclonal antibody (mAb) stimulation and cell viability. Therefore IP3R1 is not essential for T-cell development and function.
Mikoshiba Calciosignal Net Project, Exploratory Research for Advanced Technology (ERATO), c/o Banyu Pharmaceutical Co., Ltd. 2-9-3 Shimomeguro, Meguro-ku, Tokyo 153, Japan. jhirota@ims.u-tokyo.ac.jp
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Hirota
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Baba
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M
Matsumoto
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T
Furuichi
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Takatsu
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Mikoshiba
D000818:Animals; D016026:Bone Marrow Transplantation; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000172:deficiency* / Q000502:physiology; D002470:Cell Survival / Q000502:physiology / Q000528:radiation effects; D005260:Female; D053496:Inositol 1,4,5-Trisphosphate Receptors; D008213:Lymphocyte Activation / Q000502:physiology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D010641:Phenotype; D011948:Receptors, Antigen, T-Cell / Q000502:physiology*; D018160:Receptors, Cytoplasmic and Nuclear / Q000172:deficiency* / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology*; D013601:T-Lymphocytes / Q000502:physiology / Q000648:ultrastructure; D014916:Whole-Body Irradiation
D015220:Calcium Channels; C506926:ITPR1 protein, human; C506927:ITPR2 protein, human; D053496:Inositol 1,4,5-Trisphosphate Receptors; D011948:Receptors, Antigen, T-Cell; D018160:Receptors, Cytoplasmic and Nuclear; D002118:Calcium