A new protein containing an SH2 domain that inhibits JAK kinases

The proliferation and differentiation of cells of many lineages are regulated by secreted proteins known as cytokines. Cytokines exert their biological effect through binding to cell-surface receptors that are associated with one or more members of the JAK family of cytoplasmic tyrosine kinases. Cytokine-induced receptor dimerization leads to the activation of JAKs, rapid tyrosine-phosphorylation of the cytoplasmic domains, and subsequent recruitment of various signalling proteins, including members of the STAT family of transcription factors, to the receptor complex. Using the yeast two-hybrid system, we have now isolated a new SH2-domain-containing protein, JAB, which is a JAK-binding protein that interacts with the Jak2 tyrosine-kinase JH1 domain. JAB is structurally related to CIS, a cytokine-inducible SH2 protein. Interaction of JAB with Jak1, Jak2 or Jak3 markedly reduces their tyrosine-kinase activity and suppresses the tyrosine-phosphorylation and activation of STATs. JAB and CIS appear to function as negative regulators in the JAK signalling pathway.

Dynamic load at baseline can predict radiographic disease progression in medial compartment knee osteoarthritis

OBJECTIVE

To test the hypothesis that dynamic load at baseline can predict radiographic disease progression in patients with medial compartment knee osteoarthritis (OA).

METHODS

During 1991-93 baseline data were collected by assessment of pain, radiography, and gait analysis in 106 patients referred to hospital with medial compartment knee OA. At the six year follow up, 74 patients were again examined to assess radiographic changes. Radiographic disease progression was defined as more than one grade narrowing of minimum joint space of the medial compartment.

RESULTS

In the 32 patients showing disease progression, pain was more severe and adduction moment was higher at baseline than in those without disease progression (n=42). Joint space narrowing of the medial compartment during the six year period correlated significantly with the adduction moment at entry. Adduction moment correlated significantly with mechanical axis (varus alignment) and negatively with joint space width and pain score. Logistic regression analysis showed that the risk of progression of knee OA increased 6.46 times with a 1% increase in adduction moment.

CONCLUSIONS

The results suggest that the baseline adduction moment of the knee, which reflects the dynamic load on the medial compartment, can predict radiographic OA progression at the six year follow up in patients with medial compartment knee OA.

Severe osteopetrosis, defective interleukin-1 signalling and lymph node organogenesis in TRAF6-deficient mice

BACKGROUND

TRAF6, a member of the tumour necrosis factor receptor-associated factor family, was first identified as a transducer of CD40 and interleukin-1 receptor (IL-1R) signals based on the interaction of TRAF6 with the cytoplasmic tail of CD40 and with the IL-1R associated kinase in vitro. However, the functions of TRAF6 in vivo remain unidentified.

RESULTS

We show that TRAF6-/- mice exhibit severe osteopetrosis and are defective in osteoclast formation. In vitro culture experiments revealed that osteoclast precursor cells derived from TRAF6-/- mice are unable to differentiate to functional osteoclasts in response to osteoclast differentiation factor (ODF). In bone marrow of TRAF6-/- mice, the number of sIgM+B220+ immature B cells is markedly reduced while the ratio of proB to preB cells is not affected. In contrast, development of thymocytes is not affected. Furthermore, TRAF6-/- mice are defective in lymph node organogenesis and IL-1 signalling in thymocytes.

CONCLUSIONS

The results identify TRAF6 as an essential component of ODF signalling pathway, and also show that TRAF6 plays pivotal roles in immune and inflammatory systems in vivo.

Functional activation of Jak1 and Jak3 by selective association with IL-2 receptor subunits

The interleukin-2 receptor (IL-2R) consists of three subunits: the IL-2R alpha, IL-2R beta, and IL-2R gamma chains, the last of which is also used in the receptors for IL-4, IL-7, and IL-9. Stimulation with IL-2 induces the tyrosine phosphorylation and activation of the Janus kinases Jak1 and Jak3. Jak1 and Jak3 were found to be selectively associated with the "serine-rich" region of IL-2R beta and the carboxyl-terminal region of IL-2R gamma, respectively. Both regions were necessary for IL-2 signaling. Furthermore, Jak3-negative fibroblasts expressing reconstituted IL-2R became responsive to IL-2 after the additional expression of Jak3 complementary DNA. Thus, activation of Jak1 and Jak3 may be a key event in IL-2 signaling.

Involvement of receptor activator of nuclear factor kappaB ligand/osteoclast differentiation factor in osteoclastogenesis from synoviocytes in rheumatoid arthritis

OBJECTIVE

To clarify the mechanism by which osteoclasts are formed in culture of rheumatoid synoviocytes by exploring the involvement of receptor activator of nuclear factor kappaB ligand (RANKL)/osteoclast differentiation factor (ODF).

METHODS

Osteoclast formation was evaluated in cocultures of rheumatoid synovial fibroblasts and peripheral blood mononuclear cells (PBMC) in the presence of macrophage colony stimulating factor and 1,25-dihydroxyvitamin D3 (1,25[OH]2D3) utilizing separating membrane filters. RANKL/ODF expression was examined by Northern blotting in synovial tissues from 5 rheumatoid arthritis (RA) patients and tissues from patients with giant cell tumor (GCT), osteosarcoma (OS), and osteoarthritis (OA). RANKL/ODF expression and the ability of synovial fibroblasts to support osteoclastogenesis were investigated in coculture with PBMC in the presence or absence of 1,25(OH)2D3, and soluble RANKL/ODF and osteoprotegerin (OPG)/osteoclastogenesis inhibitory factor (OCIF) were measured by enzyme-linked immunosorbent assay. The effects of OPG/OCIF on the osteoclastogenesis in the primary culture of rheumatoid synoviocytes and the coculture system were determined.

RESULTS

Synovial fibroblasts did not induce osteoclastogenesis when separately cocultured with PBMC. Northern blotting revealed that RANKL/ODF was highly expressed in all tissues from RA and GCT patients, but not from OA or OS patients. Cultured rheumatoid synovial fibroblasts efficiently induced osteoclastogenesis in the presence of 1,25(OH)2D3, which was accompanied by up-regulated expression of RANKL/ODF and decreased production of OPG/OCIF. Osteoclastogenesis from synoviocytes was dose-dependently inhibited by OPG/OCIF.

CONCLUSION

RANKL/ODF expressed on synovial fibroblasts is involved in rheumatoid bone destruction by inducing osteoclastogenesis and would therefore be a good therapeutic target.

Autonomic and antiarrhythmic drug modulation of ST segment elevation in patients with Brugada syndrome

OBJECTIVES

We examined the modulatory effects of autonomic nervous system and antiarrhythmic drugs on the ST segment in patients with Brugada syndrome to gain an insight into the mechanism of ST segment elevation.

BACKGROUND

Right bundle branch block, ST segment elevation and ventricular tachyarrhythmias define a distinct clinical and electrocardiographic (ECG) syndrome (Brugada syndrome). However, the mechanism of ST segment elevation and the causes of this syndrome are unknown.

METHODS

The study included four patients in whom structural heart or coronary artery disease was excluded by noninvasive and invasive tests. High take-off ST segment elevation of either the coved or saddle-back type in precordial leads V1, V2 and V3 was seen in all patients. Three patients experienced recurrent episodes of syncope or aborted sudden cardiac death, and the remaining patient had palpitation. Autonomic receptor stimulation and blockade and intravenous administration of antiarrhythmic drugs were performed during sinus rhythm while the 12-lead ECG was recorded. Metaiodobenzylguanidine (MIBG) scanning and Holter monitoring were also performed.

RESULTS

Beta-adrenoceptor stimulation by intravenous isoproterenol consistently reduced (> or = 0.1 mV) ST segment elevation at or 80 ms after the J point in all four patients. Selective alpha-adrenoceptor stimulation by intravenous norepinephrine in the presence of propranolol or by intravenous methoxamine consistently augmented, whereas alpha-adrenoceptor blockade reduced, ST segment elevation in three patients. Intracoronary acetylcholine or intravenous edrophonium or neostigmine augmented ST segment elevation without inducing coronary spasm in three of four patients. Class IA antiarrhythmic drugs also consistently augmented (three patients), whereas class IB drugs had no effect on (two patients) ST segment elevation. No abnormality was found on MIBG imaging or heart rate variability in three patients, suggesting that autonomic dysfunction is not a primary disease process. Class IA drugs had no effect on ST segment in three control patients, suggesting that the ST segment elevation seen in patients with Brugada syndrome in response to the drugs is not a nonspecific response.

CONCLUSIONS

ST segment elevation in patients with Brugada syndrome was augmented by selective stimulation of alpha-adrenoceptors or muscarinic receptors or by class IA drugs but was mitigated by beta-adrenoceptor stimulation or alpha-adrenoceptor blockade. These responses might be explained by postulating the presence of an area of early repolarization or a local "depolarized" area in the ventricle causing ST segment elevation in this syndrome. Because only a small number of patients were studied, these possibilities need further evaluation.

The IL-2 receptor complex: its structure, function, and target genes

Proliferation of T lymphocytes is triggered by the interaction of IL-2 with its specific receptor following T lymphocyte activation. The receptor for IL-2 consists of at least three distinct subunits, the alpha chain (IL-2R alpha), the beta chain (IL-2R beta), and the gamma chain (IL-2R gamma). Although the role of IL-2R gamma in IL-2 signalling remains unclear, IL-2R beta is the subunit critical for receptor-mediated signalling. Because IL-2R beta lacks any apparent catalytic motifs, IL-2R beta may be physically or functionally coupled to other signalling molecules. Structure-function studies of IL-2R beta have revealed that at least two distinct cytoplasmic regions of IL-2R beta are involved in IL-2-induced cellular signalling. The "serine-rich" region of IL-2R beta was identified as a region critical for IL-2-induced mitotic signalling from experiments in which IL-2R beta mutant cDNAs lacking a particular cytoplasmic region or regions were expressed in an IL-3-dependent mouse pro-B cell line (BAF-B03). Meanwhile, another cytoplasmic region of IL-2R beta, the "acidic" region, is responsible for its physical association with an src-family protein tyrosine kinase (PTK), p56lck and is critical for activating the p56lck PTK following IL-2 stimulation. It is now evident that IL-2R beta is linked to at least two intracellular signalling pathways that mediate nuclear proto-oncogene induction. One pathway is linked to tyrosine phosphorylation events, mediated by a src-family protein tyrosine kinase (PTK), and that pathway leads to the induction of the c-fos, c-jun, and other genes of this family. Another pathway leads to c-myc gene induction by an as yet unknown mechanism. We discuss the complex signalling machinery that links the cell surface receptor to the nuclear events.

Relationship of Helicobacter pylori to serum pepsinogens in an asymptomatic Japanese population

A seroepidemiologic study of the prevalence of Helicobacter pylori infection in Japan was performed, and the relationship between serum pepsinogen I and II levels (markers of gastritis and gastric atrophy) and H. pylori infection was investigated. Four hundred and eighteen asymptomatic children and adults were studied. The prevalence of anti-H. pylori immunoglobulin G antibody increased with age. For persons born after 1950, the frequency of H. pylori infection increased at approximately 1% per year; for those born before 1950 the prevalence was high (70%-80%) and relatively constant. Serum pepsinogen I and II levels were significantly higher in H. pylori-infected volunteers than in H. pylori-uninfected volunteers [51.6 +/- 3 vs. 42.9 +/- 2 ng/mL (P less than 0.05) for pepsinogen I; 16.0 +/- 1 vs. 7.5 +/- 0.8 ng/mL (P less than 0.001) for pepsinogen II]. The ratio of pepsinogen I to pepsinogen II was significantly lower in H. pylori-infected volunteers (3.5 +/- 0.2) than in uninfected volunteers (6.3 +/- 0.3; P less than 0.001). The apparent decrease in prevalence of H. pylori accompanying the Westernization of Japan may eventually be accompanied by a reduction in the frequency of atrophic gastritis, the precursor lesion of the epidemic form of gastric carcinoma, and ultimately result in a decrease in the incidence of gastric carcinoma in Japan.

Identification of XAF1 as an antagonist of XIAP anti-Caspase activity

The inhibitors of apoptosis (IAPs) suppress apoptosis through the inhibition of the caspase cascade and thus are key proteins in the control of cell death. Here we have isolated the protein XIAP-associated factor 1 (XAF1) on the basis of its ability to bind XIAP, a member of the IAP family. XIAP suppresses caspase activation and cell death in vitro, and XAF1 antagonizes these XIAP activities. Expression of XAF1 triggers a redistribution of XIAP from the cytosol to the nucleus. XAF1 is ubiquitously expressed in normal tissues, but is present at low or undetectable levels in many different cancer cell lines. Loss of control over apoptotic signalling is now recognized as a critical event in the development of cancer. Our results indicate that XAF1 may be important in mediating the apoptosis resistance of cancer cells.

Age related changes in 5-methylcytosine content in human peripheral leukocytes and placentas: an HPLC-based study

The goal of the present study was to investigate inter-individual and age-dependent variation of global DNA methylation in human tissues. In this work, we examined 5-methyldeoxycytidine ((met)C) content by HPLC in human peripheral blood leukocytes obtained from 76 healthy individuals of ages varying from 4 to 94 years (yr), and 39 human placentas from various gestational stages. The HPLC analysis revealed a significant variation of (met)C across individuals and is consistent with the previous findings of age-dependent decrease of global methylation levels in human tissues. The age-dependent decrease of (met)C was relatively small, but statistically highly significant (p= 0.0002) in the aged group (65.9 +/- 8.9 [mean age +/- SD] yr; n = 22) in comparison to the young adult group (19.3 +/- 1.4 yr; n = 21). Males showed a subtle but statistically significant higher mean (met)C content than females. In contrast to the peripheral blood samples, DNA extracted from placentas exhibited gestational stage-dependent increase of methylation levels that appeared to inversely correlate with the expression levels of human endogenous retroviruses. These data may be helpful in further studies of DNA methylation, such as inheritance of epigenetic patterns, environment-induced changes, and involvement of epigenetic changes in disease.

Mice lacking H2-M complexes, enigmatic elements of the MHC class II peptide-loading pathway

We have generated mice lacking H2-M complexes, critical facilitators of peptide loading onto major histo-compatibility complex class II molecules. Ab molecules in these mice matured into stable complexes and were efficiently expressed at the cell surface. Most carried a single peptide derived from the class II-associated invariant chain; the diverse array of peptides normally displayed by class II molecules was absent. Cells from mutant mice presented both whole proteins and short peptides very poorly. Surprisingly, positive selection of CD4+ T cells was quite efficient, yielding a large and broad repertoire. Peripheral T cells reacted strongly to splenocytes from syngeneic wild-type mice, no doubt reflecting the unique peptide complement carried by class II molecules in mutant animals.

Three distinct IL-2 signaling pathways mediated by bcl-2, c-myc, and lck cooperate in hematopoietic cell proliferation

Two interleukin-2 receptor-dependent signaling pathways have thus far been identified: the c-fos/c-jun induction pathway mediated by src family protein-tyrosine kinases and the c-myc induction pathway. Here, we provide evidence for the existence of a third, rapamycin-sensitive pathway, which results in the induction of another proto-oncogene, bcl-2. In the hematopoietic cell line BAF-B03, the expression of any two of lckF505 (an active form of p56lck), Bcl-2, or c-Myc is sufficient to promote transit of the cell cycle, regardless of the activation state of the third pathway. We also provide evidence that epidermal growth factor receptor signaling may act through the same pathway that involves p56lck. These studies demonstrate a novel approach to dissecting signaling pathways regulating cellular proliferation.

Comparative study on the antibacterial activity of phytochemical flavanones against methicillin-resistant Staphylococcus aureus

Differently substituted flavanones were isolated from Leguminosae and their antibacterial activity was comparatively studied against methicillin-resistant Staphylococcus aureus (MRSA). The minimum inhibitory concentrations (MICs) of phytochemical flavanones to clinical isolates of MRSA were determined by a serial agar dilution method. The structure-activity relationship has indicated that 2',4'- or 2',6'-dihydroxylation of the B ring and 5,7-dihydroxylation of the A ring in the flavanone structure are important for significant anti-MRSA activity and that substitution with a certain aliphatic group at the 6- or 8-position also enhances the activity. Among the thirteen flavanones tested, tetrahydroxyflavanones with these structural characteristics isolated from Sophora exigua and Echinosophora koreensis showed intensive activity to inhibit the growth of all MRSA strains at 3.13-6.25 micrograms/ml. The present hydroxyflavanones would be useful in the phytotherapeutic strategy against MRSA infections.

Formation of metal-encapsulating Si cage clusters

We report the formation of a series of metal-containing hydrogenated silicon clusters using an ion trap. Mass analyses reveal that many types of transition metal ions M(+) ( M = Hf, Ta, W, Re, Ir, etc.) react with silane (SiH4) to form dehydrogenated MSi( +)(n) cluster ions ( n = 14, 13, 12, 11, 9, respectively) as an end product, indicating that the metal atom is endohedral and stabilizes the Si polyhedral cage. This finding is confirmed by our ab initio calculation that WSi12 is a W-encapsulating Si12 cage cluster, and is very stable owing to both the electronic and the geometrical shell closures.

A neoplastic epithelial duct cell line established from an irradiated human salivary gland

Transformed epithelial cells were isolated by using tissue culture techniques from an irradiated human submandibular salivary gland which showed no neoplastic lesion. These cells, carrying colony-forming ability in semisolid agar, formed a semiconfluent monolayer with occasional tubular arrangement. All transformed clones were demonstrated by electron microscopic examination to be only one type of cells having fine structure similar to intercalated duct cells. Of six clones isolated, one clone with stable growth was cultured within the sponge matrix, resulting in formation of duct-like structure with mucinous eosinophilic substance. Moreover, inoculation of the cloned cells into nude mice resulted in a production of adenocarcinoma with solid and trabecular pattern. These findings indicate that a human intercalated duct cell line carrying tumorigenicity is established from a human submandibular salivary gland with an exposure to irradiation.

O(N) methods in electronic structure calculations

Linear-scaling methods, or O(N) methods, have computational and memory requirements which scale linearly with the number of atoms in the system, N, in contrast to standard approaches which scale with the cube of the number of atoms. These methods, which rely on the short-ranged nature of electronic structure, will allow accurate, ab initio simulations of systems of unprecedented size. The theory behind the locality of electronic structure is described and related to physical properties of systems to be modelled, along with a survey of recent developments in real-space methods which are important for efficient use of high-performance computers. The linear-scaling methods proposed to date can be divided into seven different areas, and the applicability, efficiency and advantages of the methods proposed in these areas are then discussed. The applications of linear-scaling methods, as well as the implementations available as computer programs, are considered. Finally, the prospects for and the challenges facing linear-scaling methods are discussed.

Cadherin-11 expressed in association with mesenchymal morphogenesis in the head, somite, and limb bud of early mouse embryos

Cadherin-11 (cad-11) is a novel member of the cadherin family of cell adhesion molecules, having recently been identified by means of the polymerase chain reaction. To study the function and expression of this molecule, we cloned mouse, cad-11 cDNA. Transfection of L cells with cDNA led them to acquire a typical cadherin-dependent cell-cell adhesiveness, and the L cells expressing cad-11 did not coaggregate with L cells expressing E-, P-, N-, or R-cadherin when they were mixed, indicating that this novel cadherin has a homophilic binding specificity, as found for other cadherins. To determine the developmental expression pattern of this molecule, we performed in situ hybridization analysis on early mouse embryos. Cad-11 first appeared in mesodermal layers only in the head and tail regions at the mid-to-late primitive streak stages. In the head, this appearance was followed by strong expression in mesenchymal tissues including branchial arches. In the trunk, the paraxial mesoderm initially did not express cad-11. However, as the somites formed, they expressed cad-11, and this expression was strictly correlated with their initial condensation and segregation from the presomitic mesoderm. The cad-11 expression in the somites was eventually restricted to sclerotome cells. As the limb buds developed, cad-11 appeared in the distal portion of the limb mesenchyme, and, at later stages, its expression was most evident at the peripheral mesenchyme. Cad-11 was thus expressed by restricted populations of mesenchymal cells in early embryos, although it was also expressed in parts of the neural tube, such as the optic vesicle and dorsal midline, and in part of the otic vesicle. As a step to investigate the role of cad-11 in mesenchymal cell adhesion, we dissociated the limb bud mesenchyme into single cells, pelleted them, and cultured them as aggregates. In these cultures, cad-11-positive cells clearly sorted out of the negative cell population, suggesting that cad-11 might be involved in selective association of mesenchymal cells. For comparison, we studied the expression of N-cadherin and found that the expressions of these two cadherins were differential, and complementary in some tissues. These results suggest that cad-11 is involved in specific associations of subsets of mesenchymal cells and also of some neural cells during early embryogenesis.

MR cholangiopancreatography using HASTE (half-Fourier acquisition single-shot turbo spin-echo) sequences

OBJECTIVE

Images of breath-hold MR cholangiopancreatography (MRCP) using HASTE (half-Fourier acquisition single-shot turbo spin-echo) sequences were taken in healthy volunteers. The technique was then evaluated as a noninvasive alternative to direct cholangiopancreatography in patients with pancreaticobiliary diseases.

SUBJECTS AND METHODS

Forty healthy volunteers and 56 patients with various pancreaticobiliary diseases were examined by MRCP using HASTE with 128 echo train lengths on a 1.5-T MR unit. A body phased-array coll was used for data collection. Imaging times were 2 sec for the single-slice technique with a 20-mm slice thickness and 18 sec for sequential acquisition by the multislice technique with a 5-mm slice thickness (effective TE, 87 msec). We used the healthy volunteers to determine our ability to detect normal structures. The results obtained by HASTE for both patient groups were correlated with imaging by percutaneous transhepatic cholangiography or endoscopic retrograde cholangiopancreatography.

RESULTS

In all healthy volunteers, HASTE-MRCP showed both the common bile duct and the main pancreatic duct. Cystic ducts were visualized in 88% of these volunteers by HASTE-MRCP, and branches of pancreatic ducts were visualized in 75% by HASTE-MRCP. The diameter and length of dilated or stenotic ducts seen on HASTE-MRCP were correlated with percutaneous transhepatic cholangiography or endoscopic retrograde cholangiopancreatography images in 56 diseased patients. Not only the position of stenosis or dilatation but also the distal portion of the stenosis was visualized by HASTE-MRCP.

CONCLUSION

Breath-hold HASTE-MRCP with a phased-array multicoil consistently allows for high-quality images of both normal and diseased pancreaticobiliary tracts. This technique can be used as a noninvasive screening method for pancreaticobiliary diseases in the majority of patients.

Cloning of a gene cluster encoding biphenyl and chlorobiphenyl degradation in Pseudomonas pseudoalcaligenes

A gene cluster encoding biphenyl- and chlorobiphenyl-degrading enzymes was cloned from a soil pseudomonad into Pseudomonas aeruginosa PAO1161. Chromosomal DNA from polychlorinated biphenyl-degrading Pseudomonas pseudoalcaligenes KF707 was digested with restriction endonuclease XhoI and cloned into the unique XhoI site of broad-host-range plasmid pKF330. Of 8,000 transformants tested, only 1, containing the chimeric plasmid pMFB1, rendered the host cell able to convert biphenyls and chlorobiphenyls to ring meta cleavage compounds via dihydrodiols and dihydroxy compounds. The chimeric plasmid contained a 7.9-kilobase XhoI insert. Subcloning experiments revealed that the genes bphA (encoding biphenyl dioxygenase), bphB (encoding dihydrodiol dehydrogenase), and bphC (encoding 2,3-dihydroxybiphenyl dioxygenase) were coded for by the 7.9-kilobase fragment. The gene order was bphA-bphB-bphC. The hydrolase activity, which converted the intermediate meta cleavage compounds to the final product, chlorobenzoic acids, and was encoded by a putative bphD gene, was missing from the cloned 7.9-kilobase fragment.

Direct evidence for the contribution of the unique I-ANOD to the development of insulitis in non-obese diabetic mice

Insulin-dependent diabetes mellitus is characterized by the infiltration of lymphocytes into the islets of Langerhans of the pancreas (insulitis) followed by destruction of insulin-secreting beta-cells leading to overt diabetes. The best model for the disease is the non-obese diabetic (NOD) mouse. Two unusual features of the class II major histocompatibility complex (MHC) of the NOD mouse are the absence of I-E and the presence of unique I-A molecules (I-ANOD), in which aspartic acid at position 57 of the beta-chain is replaced by serine. This feature is also found in the HLA-DQ chain of many Caucasians with insulin-dependent diabetes mellitus. We have previously reported that the expression of I-E prevents the development of insulitis in NOD mouse. Here we report that the expression of I-Ak (A alpha kA beta k) in transgenic NOD mice can also prevent insulitis, and that this protection is seen not only when the I-A beta-chain has aspartic acid as residue 57, but also when this residue is serine. These results show that the single amino-acid substitution at position 57 of the I-A beta-chain from aspartic acid to serine is not sufficient for the development of the disease.

Increased susceptibility of thymocytes to apoptosis in mice lacking AIM, a novel murine macrophage-derived soluble factor belonging to the scavenger receptor cysteine-rich domain superfamily

Apoptosis of cells must be regulated both positively and negatively in response to a variety of stimuli in the body. Various environmental stresses are known to initiate apoptosis via differential signal transduction cascades. However, induction of signals that may inhibit apoptosis is poorly understood, although a number of intracellular molecules that mediate inhibition of apoptosis have been identified. Here we present a novel murine macrophage-specific 54-kD secreted protein which inhibits apoptosis (termed AIM, for apoptosis inhibitor expressed by macrophages). AIM belongs to the macrophage scavenger receptor cysteine-rich domain superfamily (SRCR-SF), members of which share a highly homologous conserved cysteine-rich domain. In AIM-deficient mice, the thymocyte numbers were diminished to half those in wild-type mice, and CD4/CD8 double-positive (DP) thymocytes were strikingly more susceptible to apoptosis induced by both dexamethasone and irradiation in vivo. Recombinant AIM protein significantly inhibited cell death of DP thymocytes in response to a variety of stimuli in vitro. These results indicate that in the thymus, AIM functions in trans to induce resistance to apoptosis within DP cells, and thus supports the viability of DP thymocytes before thymic selection.

FAK overexpression is correlated with tumour invasiveness and lymph node metastasis in oesophageal squamous cell carcinoma

Focal adhesion kinase (p125(FAK); 'FAK') is a tyrosine kinase that is localised to cellular focal adhesions and is associated with a number of other proteins, such as integrin adhesion receptors. We performed an immunohistochemical analysis of FAK protein expression to determine the relationship between FAK overexpression and clinicopathological factors in oesophageal squamous cell carcinoma (ESCC). We examined tissue specimens that had been removed from 91 patients with thoracic oesophageal cancer who had undergone surgery between 1983 and 2001. Immunohistochemical staining was performed by the standard streptavidin-biotin method. Seven human ESCC cell lines-TE-1, TE-2, TE-8, TE-13, TE-15, TT, and TTn-and one immortalized human keratinocyte cell line-HaCaT-were used in Western blot analysis. Immunostaining of FAK was seen in the cytoplasm of cancer cells, particularly in cells located in the invasive fronts of cancer nests. FAK overexpression was detected in 54 of the 91 patients (59.3%). Significant correlations were observed between FAK overexpression and cell differentiation (P=0.0057), depth of tumour invasion (P=0.0023), presence of regional lymph node metastasis (P=0.0097), number of lymph node metastases (P=0.0026), and disease stage (P=0.012). The survival rates of patients with FAK-overexpressing cancer were significantly lower than those of patients without FAK-overexpression cancer (P=0.006). The 5-year survival rate of patients without FAK overexpression was 69%, whereas that of patients with FAK overexpression was 38%. On Western blot analysis, FAK was expressed at a high level in TE-1, TE-8, TE-15, and TT cells, at a moderate level in TE-2 and TTn cells, and at a low level in TE13 and HaCaT cells. FAK phosphorylation at tyrosine 397 was demonstrated in proportion to the intensity of FAK in all cell lines except TE15 and HaCaT. In conclusion, FAK overexpression of ESCC was related to cell differentiation, tumour invasiveness, and lymph node metastasis. Consequently, patients with ESCC who had FAK overexpression had a poor prognosis.

Normal development but differentially altered proliferative responses of lymphocytes in mice lacking CD81

CD81 (TAPA-1) is a member of the transmembrane 4 superfamily (TM4SF) which is expressed on the cell surface of most cells of the body throughout their cellular differentiation. It has been recognized in several cell surface complexes of lymphocytes, suggesting that it may have diverse roles in lymphocyte development and activation regulation. Mice with a CD81 null mutation revealed normal T- and conventional B-cell development, although CD19 expression on B cells was dull and B-1 cells were reduced in number. However, both T and B cells of mutant mice exhibited strikingly enhanced proliferation in response to various types of stimuli. Interestingly, while proliferative responses of T cells following T-cell antigen receptor (TCR) engagement was enhanced in the absence of CD81, B-cell proliferation in response to B-cell antigen-receptor (BCR) cross-linking was severely impaired. Despite these altered proliferative responses, both tyrosine phosphorylation and intracellular calcium flux in response to cross-linking of cell surface antigen receptors were normal in mutant mice, reflecting apparently normal initial signaling of antigen receptors. In conclusion, though CD81 is not essential for normal T- and conventional B-cell development, it plays key roles in controlling lymphocyte homeostasis by regulating lymphocyte proliferation in distinct manners, dependent on the context of stimulation.