Armadillo repeat containing 5 (ARMC5) is a cytosolic protein with no enzymatic activities. Little is known about its function and mechanisms of action, except that gene mutations are associated with risks of primary macronodular adrenal gland hyperplasia. Here we map Armc5 expression by in situ hybridization, and generate Armc5 knockout mice, which are small in body size. Armc5 knockout mice have compromised T-cell proliferation and differentiation into Th1 and Th17 cells, increased T-cell apoptosis, reduced severity of experimental autoimmune encephalitis, and defective immune responses to lymphocytic choriomeningitis virus infection. These mice also develop adrenal gland hyperplasia in old age. Yeast 2-hybrid assays identify 16 ARMC5-binding partners. Together these data indicate that ARMC5 is crucial in fetal development, T-cell function and adrenal gland growth homeostasis, and that the functions of ARMC5 probably depend on interaction with multiple signalling pathways.

Eph kinases are the largest family of receptor tyrosine kinases, and their ligands, ephrins (EFNs), are also cell surface molecules. In this study, we investigated the role of EFNB1 and the Ephs it interacts with (collectively called EFNB1 receptors) in mouse T-cell development. In the thymus, CD8 single positive (SP) and CD4CD8 double positive (DP) cells expressed high levels of EFNB1 and EFNB1 receptors, whereas CD4 SP cells had moderate expression of both. Soluble EFNB1-Fc in fetal thymus organ culture caused significant subpopulation ratio skew, with increased CD4 SP and CD8 SP and decreased DP percentage, while the cellularity of the thymus remained constant. Moreover, in EFNB1-treated fetal thymus organ culture, CD117 ؉ , CD25 ؉ , DP, CD4 SP, and CD8 SP cells all had significantly enhanced proliferation history, according to bromodeoxyuridine uptake. In vitro culture of isolated thymocytes revealed that EFNB1-Fc on solid-phase protected thymocytes from anti-CD3-induced apoptosis, with concomitant augmentation of several antiapoptotic factors, particularly in CD4 SP and CD8 SP cells; on the other hand, soluble EFNB1-Fc promoted anti-CD3-induced apoptosis, as was the case in vivo. This study reveals that EFNB1 and EFNB1 receptors are critical in thymocyte development.Receptors are important cell surface molecules for communication between cells and their environment. Protein-tyrosine kinases are essential components in lymphocyte signaling pathways. Thus, receptor tyrosine kinases have dual pivotal functions in lymphocytes. The Eph kinases are the largest receptor protein-tyrosine kinase family. According to sequence homology, Eph kinases are classified into EphAs (EphA1-EphA9) and EphBs (EphB1-EphB6) (1) (available on the World Wide Web at cbweb.med.harvard.edu/eph-nomenclature/ cell_letter.html). Ephrins (EFNs), 4 ligands of Eph kinases, are cell surface molecules as well and can be classified into A and B subfamilies. EFNAs (EFNA1-EFNA6) are glycosylphosphatidylinositol-anchored proteins and bind to EphA members with loose specificity; EFNBs (EFNB1-EFNB3) are transmembrane proteins and bind to EphBs, again with loose specificity (1). EphA4, an exception, can bind to EFNB2 in addition to EFNA members (2). EFNBs can also function as reciprocal receptors for EphB molecules and reversely transduce signals into cells (3). Most Eph kinases or EFNs have probably already been identified, because sequences from the human genome project have revealed 14 Eph entries and eight EFN entries (4).Since Eph kinases and their ligands are all cell surface molecules, they can only interact with each other when expressed on adjacent cells. Not surprisingly, the clearly demonstrated function of these receptors and ligands is to control accurate spatial patterning and cell positioning in the central nervous (5, 6) and gastrointestinal (7) some EphAs and EFNAs interfere with T-cell development in thymic organ culture (21). EFNA1 can inhibit T-cell chemotaxis (22). The thymus is the cradle of T cells. Early T-lineage cells in th...

We assessed the autoantibody repertoire of a mouse model engineered to develop breast cancer and the repertoire of autoantibodies in plasmas collected at a pre-clinical time point and at the time of clinical diagnosis of breast cancer. In seeking to identify common pathways, networks and protein families associated with the humoral response, we elucidated the dynamic nature of tumor antigens and autoantibody interactions. Lysate proteins from an immortalized cell line from an MMTV-neu mouse model and from MCF7 human breast cancers were spotted onto nitrocellulose microarrays and hybridized with mouse and human plasma samples, respectively. Ig-based plasma immunoreactivity against glycolysis and spliceosome proteins was a predominant feature observed both in tumor bearing mice and in pre-diagnostic human samples. Interestingly, autoantibody reactivity was more pronounced further away than closer to diagnosis. We provide evidence for dynamic changes in autoantibody reactivity with tumor development and progression that may depend in part on the extent of antigen-antibody interactions.

Drak2 is a death-associated protein family serine-threonine kinase. Its expression and roles in the immune system were investigated in this study. According to in situ hybridization, Drak2 expression was ubiquitous at the mid-gestation stage in embryos, followed by more focal expression in various organs in the perinatal period and adulthood, notably in the thymus, spleen, lymph nodes, cerebellum, suprachiasmatic nuclei, pituitary, olfactory lobes, adrenal medulla, stomach, skin, and testes. Drak2 transgenic (Tg) mice were generated using the human ␤-actin promoter. These Tg mice showed normal T cell versus B cell and CD4 versus CD8 populations in the spleen, but their spleen weight cellularity was lower in comparison with wild type mice. After TCR activation, the proliferation response in Drak2 Tg T cells was normal, although their interleukin (IL)-2 and IL-4 but not interferon-␥ production was augmented. Activated Drak2 Tg T cells demonstrated significantly enhanced apoptosis in the presence of exogenous IL-2. At the molecular level, Drak2 Tg T cells manifested a lower increase of anti-apoptotic factors during activation; such a change probably rendered the cells vulnerable to subsequent IL-2 insults. The compromised apoptosis in Drak2 Tg T cells was associated with reduced numbers of T cells with the memory cell phenotype (CD62L lo ) and repressed secondary T cell responses in delayed type hypersensitivity. Our study demonstrates that Drak2 expresses in the T cell compartment but is not T cell-specific; it plays critical roles in T cell apoptosis and memory T cell development.To elucidate the molecular mechanisms of T cell activation and differentiation, we conducted DNA microarray analysis employing the mouse 15,000 cDNA panel of the NIA, National Institutes of Health, to compare gene expression patterns of resting versus activated T cells (anti-CD3 and anti-CD28 stimulation for 24 h). Drak2 was one of the genes found to undergo significant changes after activation and was thus selected for further investigation.Drak2 is a serine/threonine kinase belonging to a family of deathassociated protein (DAP) 3 kinases that consists of DAP (1), DRP-1 (2), ZIP kinase (3), DAPK2 (4), Drak1, and Drak2 (5). Drak1 and Drak2 share 67.1% identity in their kinase domain and 24.2% identity in their noncatalytic regions (5). Drak2 also shares about 50% identity in the kinase domain with other members of the family (2). Although DAP, DRP-1, and DAPK2 have a calmodulin regulatory domain in their C terminus, ZIP, Drak1, and Drak2 do not (1-5). DAP, DAPK2, and DRP-1 are localized in the cytosol (1, 2, 4), ZIP kinase and Drak1 resides mainly in the nuclei (3, 5), and Drak2 is found in both the cytosol and nuclei (5, 6), suggesting different mechanisms of action. When DAP family kinases are overexpressed in various cells, apoptosis ensues, either directly or after cytokine stimulation (1-5), indicating their involvement in apoptosis.The mechanism of action and regulation of the prototype DAP family kinase, DAP, at the molecular le...