Store-operated Ca2+ entry through ORAI1 is critical for T cell-mediated autoimmunity and allograft rejection

ORAI1 is the pore-forming subunit of the Ca(2+) release-activated Ca(2+) (CRAC) channel, which is responsible for store-operated Ca(2+) entry in lymphocytes. A role for ORAI1 in T cell function in vivo has been inferred from in vitro studies of T cells from human immunodeficient patients with mutations in ORAI1 and Orai1(-/-) mice, but a detailed analysis of T cell-mediated immune responses in vivo in mice lacking functional ORAI1 has been missing. We therefore generated Orai1 knock-in mice (Orai1(KI/KI)) expressing a nonfunctional ORAI1-R93W protein. Homozygosity for the equivalent ORAI1-R91W mutation abolishes CRAC channel function in human T cells resulting in severe immunodeficiency. Homozygous Orai1(KI/KI) mice die neonatally, but Orai1(KI/KI) fetal liver chimeric mice are viable and show normal lymphocyte development. T and B cells from Orai1(KI/KI) mice display severely impaired store-operated Ca(2+) entry and CRAC channel function resulting in a strongly reduced expression of several key cytokines including IL-2, IL-4, IL-17, IFN-γ, and TNF-α in CD4(+) and CD8(+) T cells. Cell-mediated immune responses in vivo that depend on Th1, Th2, and Th17 cell function were severely attenuated in ORAI1-deficient mice. Orai1(KI/KI) mice lacked detectable contact hypersensitivity responses and tolerated skin allografts significantly longer than wild-type mice. In addition, T cells from Orai1(KI/KI) mice failed to induce colitis in an adoptive transfer model of inflammatory bowel disease. These findings reaffirm the critical role of ORAI1 for T cell function and provide important insights into the in vivo functions of CRAC channels for T cell-mediated immunity.     

Physiological requirements for 20-hydroxyecdysone-induced rectal sac distention in the pupa of the silkworm, Bombyx mori

Successful insect development is achieved via appropriate fluctuation of ecdysteroid levels. When an insect's ecdysteroid level is disrupted, physiological and developmental defects occur. In the pupa of the silkworm, Bombyx mori, the rectal sac is an essential organ that operates as a repository for degraded ecdysteroids, and it can be distended by administration of 20-hydroxyecdysone (20E). Our previous study showed that rectal sac distention appears 4 days after 20E administration. Hemolymph ecdysteroid levels, however, decrease to lower level during this period. Thus, the timing of the rectal sac distention does not match with that of ecdysteroid elevation. Here, we examine how 20E induces rectal sac distention. A ligature experiment and ecdysteroid quantification showed that continuous 20E stimulation induces rectal sac distention. Thorax tissue contributed to the continuous 20E stimulation needed to induce distention. Ecdysteroid released from the thorax tissue may be converted to 20E by ecdysone 20-hydroxylase to produce continuous 20E stimulation. Thus, the ecdysone metabolic pathway plays a critical role in rectal sac distention.     

Involvement of IL-10 and Bcl-2 in resistance against an asbestos-induced apoptosis of T cells

To analyze the possibility that immunological alteration in asbestos-related diseases (ARDs) such as asbestosis (ASB) and malignant mesothelioma (MM) may affect the progression of cancers, a human adult T cell leukemia virus-immortalized T cell line (MT-2Org) was continuously exposed to 10 μg/ml of chrysotile-B (CB), an asbestos. After at least 8 months of exposure, the rate of apoptosis in the cells became very low and the resultant subline was designated MT-2Rst. The MT-2Rst cells were characterized by (i) enhanced expression of bcl-2, with regain of apoptosis-sensitivity by reduction of bcl-2 by siRNA, (ii) excess IL-10 secretion and expression, and (iii) activation of STAT3 that was inhibited by PP2, a specific inhibitor of Src family kinases. These results suggested that the contact between cells and asbestos may affect the human immune system and trigger a cascade of biological events such as activation of Src family kinases, enhancement of IL-10 expression, STAT3 activation and Bcl-2 overexpression. This speculation was partially confirmed by the detection of elevated bcl-2 expression levels in CD4 + peripheral blood T cells from patients with MM compared with those from patients with ASB or healthy donors. Further studies will be required to verify the role of T cells with enhanced bcl-2 expression in tumor progression induced by asbestos exposure.     

Embryonic dermal condensation and adult dermal papilla induce hair follicles in adult glabrous epidermis through different mechanisms

Hair induction in the adult glabrous epidermis by the embryonic dermis was compared with that by the adult dermis. Recombinant skin, composed of the adult sole epidermis and the embryonic dermis containing dermal condensations (DC), was transplanted onto the back of nude mice. The epidermis of transplants formed hairs. Histology on the induction process demonstrated the formation of placode-like tissues, indicating that the transplant produces hair follicles through a mechanism similar to that underlying hair follicle development in the embryonic skin. An isolated adult rat sole skin piece, inserted with either an aggregate of cultured dermal papilla (DP) cells or an intact DP between its epidermis and dermis, was similarly transplanted. The transplant produced hair follicles. Histology showed that the epidermis in both cases surrounded the aggregates of DP cells. The epidermis never formed placode-like tissues. Thus, it was concluded that the adult epidermal cells recapitulate the embryonic process of hair follicle development when exposed to DC, whereas they get directly into the anagen of the hair cycle when exposed to DP. The expression pattern of Edar and Shh genes, and P-cadherin protein during the hair follicle development in the two types of transplants supported the above conclusion.     

The thioredoxin gene family in rice: genome-wide identification and expression profiling under different biotic and abiotic treatments

Thioredoxin (TRX) is a multi-functional redox protein. Genome-wide survey and expression profiles of different stresses were observed. Conserved amino acid residues and phylogeny construction using the OsTRX conserved domain sequence suggest that the TRX gene family can be classified broadly into six subfamilies in rice. We compared potential gene birth-and-death events in the OsTRX genes. The Ka/Ks ratio is a measure to explore the mechanism and 3 evolutionary stages of the OsTRX genes divergence after duplication. We used 270 TRX genes from monocots and eudicots for synteny analysis. Furthermore, we investigated expression profiles of this gene family under 5 biotic and 3 abiotic stresses. Several genes were differentially expressed with high levels of expression and exhibited subfunctionalization and neofunctionalization after the duplication event response to different stresses, which provides novel reference for the cloning of the most promising candidate genes from OsTRX gene family for further functional analysis.