Measles virus continues to be a major killer of children, claiming roughly one million lives a year. Measles virus infection causes profound immunosuppression, which makes measles patients susceptible to secondary infections accounting for high morbidity and mortality. The Edmonston strain of measles virus, and vaccine strains derived from it, use as a cellular receptor human CD46 (refs 3, 4), which is expressed on all nucleated cells; however, most clinical isolates of measles virus cannot use CD46 as a receptor. Here we show that human SLAM (signalling lymphocyte-activation molecule; also known as CDw150), a recently discovered membrane glycoprotein expressed on some T and B cells, is a cellular receptor for measles virus, including the Edmonston strain. Transfection with a human SLAM complementary DNA enables non-susceptible cell lines to bind measles virus, support measles virus replication and develop cytopathic effects. The distribution of SLAM on various cell lines is consistent with their susceptibility to clinical isolates of measles virus. The identification of SLAM as a receptor for measles virus opens the way to a better understanding of the pathogenesis of measles virus infection, especially the immunosuppression induced by measles virus.

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Both CD46 and signaling lymphocytic activation molecule (SLAM) have been shown to act as cellular receptors for measles virus (MV). The viruses on throat swabs from nine patients with measles in Japan were titrated on Vero cells stably expressing human SLAM. Samples from all but two patients produced numerous plaques on SLAM-expressing Vero cells, whereas none produced any plaques on Vero cells endogenously expressing CD46. The Edmonston strain of MV, which can use either CD46 or SLAM as a receptor, produced comparable titers on these two types of cells. The results strongly suggest that the viruses in the bodies of measles patients use SLAM but probably not CD46 as a cellular receptor.Measles virus (MV) is an enveloped negative-strand RNA virus of the Morbillivirus genus in the Paramyxoviridae family (4). Measles remains an important cause of childhood mortality, with approximately one million deaths per year worldwide (2), mainly due to secondary infections caused by MV-induced immunosuppression (4). Human CD46 has been shown to be a cellular receptor for vaccine strains of MV, such as the Edmonston strain (3, 10). However, wild-type MV strains that are commonly isolated in marmoset B-cell line B95a or human B-cell lines usually do not use CD46 as a receptor (5-7, 14, 15, 18), although a study has reported that MV strains isolated from and propagated only in human peripheral blood mononuclear cells (PBMCs) use CD46 as a receptor (9). We have recently demonstrated that signaling lymphocytic activation molecule (SLAM; also known as CDw150) is a cellular receptor for MV, including the Edmonston strain, B95a-isolated strains, and PBMC-isolated strains (20). Thus, some MV strains use SLAM but not CD46 as a receptor, and others, such as the Edmonston strain, use either SLAM or CD46. The type of MV strain obtained depends on the cell types used for virus isolation. In this study, we sought to quantitate the proportions of these two types of MV in measles patients.Vero cells are susceptible to the Edmonston strain but not to B95a-isolated MV strains (6, 18). In order to titrate B95a-isolated MV strains on Vero cells, we transfected them with the expression plasmid encoding human SLAM (pCAGhSLAM) (12) and the vector plasmid pCXN2 (11) containing the neomycin resistance (neo) gene; we selected stable clones in the presence of G418. We used the clone expressing the highest level of human SLAM (Vero/hSLAM) in the following experiments.The expression profile of Vero/hSLAM cells stained with anti-human SLAM monoclonal antibody IPO-3 (Kamiya Biomedical) (17) is shown in Fig. 1A. Vero/hSLAM cells were infected with the B95a-isolated KA strain of MV (18-20) at a multiplicity of infection of 0.1. At 24 h after infection, they developed extensive syncytia (Fig. 1B), unlike the parental Vero cells (6, 18). Then, we used Vero and Vero/hSLAM cells for plaque titration of the KA strain. Vero/hSLAM cells developed clear plaques after infection with the KA strain, whereas Vero cells inoculated with the same amount of the virus did no...

IC323-EGFP infection of SLAM-negative cells. This infection occurred under conditions in which entry via endocytosis was inhibited. These results indicate that MV can infect a variety of cells, albeit with a low efficiency, by using an as yet unidentified receptor(s) other than SLAM or CD46, in part explaining the observed MV infection of SLAM-negative cells in vivo.Measles virus (MV) is an enveloped virus of the Morbillivirus genus in the Paramyxoviridae family and has a linear, nonsegmented, negative-strand RNA genome with two envelope glycoproteins, the hemagglutinin (H) and fusion (F) proteins (12). Despite the development of effective live vaccines, measles remains a significant cause of infant mortality worldwide, mainly due to secondary infections caused by MV-induced immunosuppression (12).Vaccine strains of MV such as the Edmonston strain use human CD46 as a cellular receptor (9, 25). Since CD46 is expressed on all nucleated human cells (19), vaccine strains of MV can infect almost any human cell line. In contrast, wildtype strains of MV isolated in the marmoset B-cell line B95a or human B-cell lines are usually unable to use CD46 as a receptor (6,13,17,18,36,37,46,47). Recently, we have demonstrated that signaling lymphocyte activation molecule (SLAM; also known as CD150) acts as a cellular receptor for both vaccine and wild-type strains of MV (48). SLAM is a costimulatory molecule in lymphocyte activation (7), and its expression is restricted to activated T and B lymphocytes, immature thymocytes (7, 41), mature dendritic cells (26), and activated monocytes (23), nicely explaining the tropism of MV as well as the lymphopenia and immunosuppression observed in MV infection. We have also reported that viruses obtained from clinical specimens (throat swabs of measles patients) use SLAM but not CD46 as a receptor (28). Previous histopathological studies in vivo, however, have revealed that in addition to infecting SLAM-positive cells of the immune system, MV also infects endothelial (11, 15, 16, 21, 24), epithelial (21, 24, 44), and neuronal cells (3,24,40), none of which have been shown to express SLAM (7, 41). Thus, the in vivo receptor usage of MV remains to be determined.Reverse genetics technology has enabled us to study a number of important problems concerning virus replication and pathogenesis. As for MV, the rescue of the Edmonston strain from cloned DNA was developed in 1995 (32), providing us with many insights into MV biology (10,30,31,35,49,50). However, since the vaccine strain does not exhibit pathogenicity in experimentally infected monkeys (1, 17), results obtained with it may not be applicable to clinical problems in vivo. Recently, Takeda et al. have successfully developed the rescue system of a wild-type MV strain that could reproduce the natural course of MV pathology in monkeys, opening the way to molecularly dissecting the pathogenesis of MV infection at the level of viral genomes (45).In this study, we examined MV entry into SLAM-negative cells. To facilitate the analysis, we recove...

Pathogens or pathogen-associated molecular patterns can signal to cells of the innate immune system and trigger effective adaptive immunity. However, relatively little is known about how the innate immune system detects tissue injury or necrosis. Evidence suggests that the release of heat-shock proteins (HSPs) may provide adjuvant-like signals, but the ability of HSPs to promote activation or tolerance in vivo has not been addressed. In this study we show that Hsp70 promotes dendritic cell (DC) function and, together with antigen, triggers autoimmune disease in vivo.

Stomatal pores surrounded by a pair of guard cells in the plant epidermis control gas exchange between plants and the atmosphere in response to light, CO 2 , and the plant hormone abscisic acid. Light-induced stomatal opening is mediated by at least three key components: the blue light receptor phototropin (phot1 and phot2), plasma membrane H + -ATPase, and plasma membrane inward-rectifying K + channels. Very few attempts have been made to enhance stomatal opening with the goal of increasing photosynthesis and plant growth, even though stomatal resistance is thought to be the major limiting factor for CO 2 uptake by plants. Here, we show that transgenic Arabidopsis plants overexpressing H + -ATPase using the strong guard cell promoter GC1 showed enhanced light-induced stomatal opening, photosynthesis, and plant growth. The transgenic plants produced larger and increased numbers of rosette leaves, with ∼42-63% greater fresh and dry weights than the wild type in the first 25 d of growth. The dry weights of total flowering stems of 45-d-old transgenic plants, including seeds, siliques, and flowers, were ∼36-41% greater than those of the wild type. In addition, stomata in the transgenic plants closed normally in response to darkness and abscisic acid. In contrast, the overexpression of phototropin or inward-rectifying K + channels in guard cells had no effect on these phenotypes. These results demonstrate that stomatal aperture is a limiting factor in photosynthesis and plant growth, and that manipulation of stomatal opening by overexpressing H + -ATPase in guard cells is useful for the promotion of plant growth.Arabidopsis thaliana | stomatal conductance | photosynthetic rate | biomass

SAP is an adaptor mutated in X-linked lymphoproliferative disease. It plays a critical role in T helper 2 (T(H)2) cytokine production. This function was suggested to reflect the capacity of SAP to associate with SLAM family receptors and enable tyrosine phosphorylation signaling by these receptors through SAP-mediated recruitment of Src-related kinase FynT. Here, we addressed by genetic means the importance of the SAP-FynT interaction in normal T cell functions. By creating a mouse in which the FynT binding site of SAP was inactivated in the germ line (sap(R78A) mouse) and by analyzing mice lacking SAP, FynT or SLAM, evidence was obtained that the SAP-FynT cascade is indeed crucial for normal T(H)2 functions in vitro and in vivo. These data imply that SAP is necessary for T(H)2 cytokine regulation primarily as a result of its capacity to recruit FynT. They also establish a previously unappreciated role for FynT in SAP-dependent T(H)2 cytokine regulation.

Stomatal pores surrounded by a pair of guard cells in the plant epidermis control gas exchange for photosynthesis in response to light, CO(2), and phytohormone abscisic acid. Phototropins (phot1 and phot2) are plant blue-light receptor kinases and mediate stomatal opening via activation of the plasma membrane H(+)-ATPase. However, the signaling mechanism from phototropins to the H(+)-ATPase has yet to be determined. Here, we show that FLOWERING LOCUS T (FT) is expressed in guard cells and regulates stomatal opening. We isolated an scs (suppressor of closed-stomata phenotype in phot1 phot2) 1-1 mutant of Arabidopsis thaliana and showed that scs1-1 carries a novel null early flowering 3 (elf3) allele in a phot1 phot2 background. scs1-1 (elf3 phot1 phot2 triple mutant) had an open-stomata phenotype with high H(+)-ATPase activity and showed increased levels of FT mRNA in guard cells. Transgenic plants overexpressing FT in guard cells showed open stomata, whereas a loss-of-function FT allele, ft-1, exhibited closed stomata and failed to activate the H(+)-ATPase in response to blue light. Our results define a new cell-autonomous role for FT and demonstrate that the flowering time genes ELF3 and FT are involved in the regulation of H(+)-ATPase by blue light in guard cells.