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Severe acute respiratory syndrome coronavirus (SARS-CoV) is a highrisk infectious pathogen. In the proposed model of respiratory failure, SARS-CoV down-regulates its receptor, angiotensin-converting enzyme 2 (ACE2), but the mechanism involved is unknown. We found that the spike protein of SARS-CoV (SARS-S) induced TNF-␣-converting enzyme (TACE)-dependent shedding of the ACE2 ectodomain. The modulation of TACE activity by SARS-S depended on the cytoplasmic domain of ACE2, because deletion mutants of ACE2 lacking the carboxyl-terminal region did not induce ACE2 shedding or TNF-␣ production. In contrast, the spike protein of HNL63-CoV (NL63-S), a CoV that uses ACE2 as a receptor and mainly induces the common cold, caused neither of these cellular responses. Intriguingly, viral infection, judged by real-time RT-PCR analysis of SARS-CoV mRNA expression, was significantly attenuated by deletion of the cytoplasmic tail of ACE2 or knock-down of TACE expression by siRNA. These data suggest that cellular signals triggered by the interaction of SARS-CoV with ACE2 are positively involved in viral entry but lead to tissue damage. These findings may lead to the development of anti-SARS-CoV agents.shedding ͉ cytoplasmic tail ͉ HNL63-CoV ͉ TNF-␣ S evere acute respiratory syndrome coronavirus (SARS-CoV) is an infectious pathogen known to have caused acute respiratory distress in Ͼ8,000 patients with a mortality rate of Ϸ10% (1). Although outbreaks of SARS-CoV are now well controlled, the mechanism of severe respiratory failure in infected patients is unknown. Angiotensin-converting enzyme 2 (ACE2), an ACE homolog that functions as a positive regulator of the reninangiotensin system (RAS) (2, 3), was identified as a receptor of SARS-CoV (4). A possible indicator of a severe clinical outcome, the spike protein of SARS-CoV (SARS-S) was found to downregulate ACE2 expression (5). ACE2 knockout (KO) mice were also shown to be susceptible to severe respiratory failure after chemical challenge (5, 6), and ACE2 has been shown to moderate ACE-induced intracellular inflammation, suggesting that the mechanism of ACE2 down-regulation may explain the molecular basis of SARS-CoV-related severe respiratory distress.HNL63-CoV, a CoV (7) that causes the common cold, was recently found to use ACE2 for viral infection (8), and it was further shown that the spike protein of HNL63-CoV (NL63-S) binds ACE2 directly (9). NL63-S and SARS-S show 21% identity (10), whereas that between NL63-S and the spike protein of HCoV-229E, which uses CD13 [a completely different carboxy (C)-peptidase] as a cellular receptor (11), is 55%. It is important to note that, despite their phylogenetically distinct properties and their producing different clinical outcomes, SARS-CoV and HNL63-CoV both use ACE2.Based on these observations, we hypothesized that the functional modulation of ACE2 may be differentially induced by SARS-S and NL63-S. To test this prediction, we first clarified the mechanism of SARS-S-induced ACE2 down-regulation, and then compared the cellular respon...

Point mutations that activate the Ki-ras proto-oncogene are presented in about 50 percent of human colorectal tumors. To study the functional significance of these mutations, the activated Ki-ras genes in two human colon carcinoma cell lines, DLD-1 and HCT 116, were disrupted by homologous recombination. Compared with parental cells, cells disrupted at the activated Ki-ras gene were morphologically altered, lost the capacity for anchorage-independent growth, grew more slowly both in vitro and in nude mice, and showed reduced expression of c-myc. Thus, the activated Ki-ras gene plays a key role in colorectal tumorigenesis through altered cell differentiation and cell growth.

SUMMARY PIK3CA and PTEN alterations are common in human cancer, but only a fraction of such tumors are dependent upon AKT signaling. AKT-independence is associated with redundant activation of cap-dependent translation mediated by convergent regulation of the translational repressor 4E-BP1 by the AKT and ERK pathways. This provides mechanistic bases for the limited activity of AKT and MEK inhibitors in tumors with co-mutation of both pathways and the profound synergy observed with combined inhibition. Whereas such tumors are sensitive to a dominant active 4E-BP1 mutant, knockdown of 4E-BP1 expression reduces their dependence on AKT/ERK signaling for translation or survival. Thus, 4E-BP1 plays a prominent role in mediating the effects of these pathways in tumors in which they are activated by mutation.

Cell migration is a fundamental biological process involving membrane polarization and cytoskeletal dynamics, both of which are regulated by Rho family GTPases. Among these molecules, Rac is crucial for generating the actin-rich lamellipodial protrusion, a principal part of the driving force for movement. The CDM family proteins, Caenorhabditis elegans CED-5, human DOCK180 and Drosophila melanogaster Myoblast City (MBC), are implicated to mediate membrane extension by functioning upstream of Rac. Although genetic analysis has shown that CED-5 and Myoblast City are crucial for migration of particular types of cells, physiological relevance of the CDM family proteins in mammals remains unknown. Here we show that DOCK2, a haematopoietic cell-specific CDM family protein, is indispensable for lymphocyte chemotaxis. DOCK2-deficient mice (DOCK2-/-) exhibited migration defects of T and B lymphocytes, but not of monocytes, in response to chemokines, resulting in several abnormalities including T lymphocytopenia, atrophy of lymphoid follicles and loss of marginal-zone B cells. In DOCK2-/- lymphocytes, chemokine-induced Rac activation and actin polymerization were almost totally abolished. Thus, in lymphocyte migration DOCK2 functions as a central regulator that mediates cytoskeletal reorganization through Rac activation.

Genomic typing of class I HLA alleles adds substantially to the success of transplantation of hematopoietic stem cells from unrelated donors, even if the donors are serologically identical to their recipients with respect to HLA-A, B, and DR antigens.

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Rheumatoid arthritis (RA) is a common autoimmune disease with a complex genetic etiology. Herein we identify a single-nucleotide polymorphism (SNP) in the promoter region of FcRH3, a member of the Fc receptor homolog family, that is associated with RA susceptibility (OR=2. 15, P=0.00000085). This polymorphism alters the binding affinity of nuclear factor-κB and regulates NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author ManuscriptFcRH3 expression. High FcRH3 expression on B-cells and augmented autoantibody production were observed in individuals with the disease-susceptible genotype. Associations were also found between the SNP and susceptibility to autoimmune thyroid disease and systemic lupus erythematosus. FcRH3 may thus play a pivotal role in autoimmunity.Rheumatoid arthritis represents one of the most common autoimmune diseases, and is characterized by inflammation of synovial tissue and joint destruction. Although the disease is believed to result from a combination of genetic and environmental factors, the complete etiology of RA has not yet been clarified 1 . While specific haplotypes of human leukocyte antigen (HLA)-DRB1, usually referred to as shared-epitope (SE) sequences 2 , have been repeatedly reported as conferring RA-susceptibility 3,4 , other genetic components are also involved in the pathogenesis of RA 5 . This combination of HLA haplotypes and non-HLA genes accounting for disease susceptibility is also seen in other autoimmune diseases 6-8 . In autoimmune thyroid disease (AITD), for instance, studies have consistently shown that the HLA-DR3 haplotype is associated with disease risk, in addition to a functional haplotype of a non-HLA gene, CTLA4, that has recently been associated with AITD susceptibility 9 .Identification of non-HLA genes associated with RA susceptibility and other autoimmunities seems difficult, due to the low relative risk of disease resulting from these non-HLA genes compared with the strong relative risk from disease-associated HLA haplotypes. In a search for non-HLA determinants of disease susceptibility, whole genome studies have been conducted for both human autoimmune diseases and experimental animal models. These studies have revealed non-random clustering of susceptibility loci for clinically distinct diseases 8,10 . This overlapping of susceptibility loci for multiple autoimmunities suggests the existence of common susceptibility genes in those regions. Intense studies of loci-clustering regions has revealed genes commonly associated with multiple autoimmune diseases, such as CTLA4 on 2q33 (ref. and Idd17 (ref. 25)). Although 1q21-23 is a strong candidate region for RA susceptible genes, as above mentioned, the association of classical FcγRs with disease susceptibility remains controvertial 26,27 . The present study focused on the 1q21-23 region to identify RA-associated genes in Japanese subjects using linkage disequilibrium (LD) mapping. RESULTS Case-control study by SNP-based LD-mapping in 1q21-23To evaluate the extent of association, we a...