Smac, a mitochondrial protein that promotes cytochrome c-dependent caspase activation by eliminating IAP inhibition

We report here the identification of a novel protein, Smac, which promotes caspase activation in the cytochrome c/Apaf-1/caspase-9 pathway. Smac promotes caspase-9 activation by binding to inhibitor of apoptosis proteins, IAPs, and removing their inhibitory activity. Smac is normally a mitochondrial protein but is released into the cytosol when cells undergo apoptosis. Mitochondrial import and cleavage of its signal peptide are required for Smac to gain its apoptotic activity. Overexpression of Smac increases cells' sensitivity to apoptotic stimuli. Smac is the second mitochondrial protein, along with cytochrome c, that promotes apoptosis by activating caspases.

Formation of calcium phosphate/collagen composites through mineralization of collagen matrix

Several types of calcium phosphate/collagen composites, including noncrystalline calcium phosphate/collagen, poorly crystalline carbonate-apatite (PCCA)/collagen, and PCCA + tetracalcium phosphate/collagen composites, were prepared through the mineralization of collagen matrix. The type I collagen was presoaked with a PO(3-)(4) containing solution and then immersed in a Ca(2+) containing solution to allow mineral deposition. The solution of 0.56 M sodium dibasic phosphate (Na(2)HPO(4)) with a pH of nearly 14 was metastable and its crystallization produced Na(2)HPO(4) and sodium tripolyphosphate hexahydrate (Na(5)P(3)O(10)). 6H(2)O), leading to a controlled release of orthophosphate ions during the subsequent mineral precipitation. The development of the composites was investigated in detail. The mineral contributed up to 60-70% of the weight of the final composites. The strength and Young's modulus of the composites in tensile tests overlapped the lower range of values reported for bone. When implanted in muscle tissue, the composite showed biodegradability that was partly through a multinucleated giant cell mediated process. In a bone explant culture model it was observed that bone-derived cells deposited mineralizing collagenous matrix on the composite.

DFF45/ICAD can be directly processed by granzyme B during the induction of apoptosis

Granzyme B (GzmB) is a component of cytotoxic lymphocyte granules that can rapidly initiate apoptosis in target cells. While several procaspases are cleaved and activated by GzmB, the absolute requirement of caspase activation for GzmB-induced apoptosis is controversial. In this report, we demonstrate that GzmB can initiate apoptosis in the absence of caspase-3 activity by directly cleaving DFF45/ICAD to liberate activated DFF40/CAD. DFF45/ICAD cleavage occurs less efficiently in cells that lack caspase-3 activity, suggesting that the caspases normally amplify the GzmB death signal. DFF45/ICAD-deficient mouse embryo fibroblasts are partially resistant to GzmB-induced death, demonstrating the biological importance of DFF45/ICAD for GzmB-mediated apoptosis.

[Micro-anatomy of the apical lateral foramina of permanent teeth]

OBJECTIVE

To provide data of apical lateral foramina of Chinese people's permanent teeth.

METHODS

The shape and diameter of the apical lateral foramina in 1,502 permanent teeth were observed under the XTL-2 stero-microscope.

RESULTS

The shape and diameter of 230 apical lateral foramina in the permanent teeth can be divided into four types: round (61.31%, diameter: 0.09-0.26 mm), oval (36.96%, diameter: 0.12-0.28 mm), renal (1.30%), and irregular (0.43%). The occurrence of the apical lateral foramina is 15.31% (230/1,502).

CONCLUSIONS

The apical lateral foramina are found in 1/7 of 1,502 permanent teeth.

[Comparative study of three common G6PD gene mutations in Yao and Han People in Guangxi]

OBJECTIVE

To study G6PD gene mutation diversity in Yao and Han people in Guangxi and compare the genotypic frequencies.

METHODS

The three common G6PD gene mutations in Chinese were investigated in 34 G6PD deficient individuals from Yao and 37 from Han people by using an amplification refractory mutation system (ARMS).

RESULTS

Among 34 cases of G6PD deficiency of Yao people, the genotypic frequencies of G1376T, G1388A and A95G were 41.2%, 26.5% and 14.7%, respectively. A case of C1311T was detected. As compared with that in Han people, the respective frequencies were 16.2%, 40.6% and 5.4%.

CONCLUSION

The main G6PD mutations in Yao people were the same with Han people in Guangxi, but G1376T mutation was higher than that in Han people. The C1311T mutation in Yao people in Guangxi was reported for the first time.

Adult Apaf-1-deficient mice exhibit male infertility

Release of cytochrome c from the mitochondria, and subsequent binding to apoptotic protease-activating factor-1 (Apaf-1), is a key trigger of apoptotic events. A complex composed of Apaf-1, dATP, and cytochrome c activates a series of cytoplasmic proteases called caspases, leading to apoptotic cell death. We have disrupted the Apaf-1 gene in the mouse. Like previous reports on this knockout model, we find that most Apaf-1 mutants die perinatally and frequently exhibit exencephaly and cranioschesis. We additionally find that the neural lesions that develop in the knockout are due to an excess of neural progenitor cells that manifests as early as embryonic day 9.5 in development. In contrast to previous reports on the Apaf-1 knockout mice, we find that 5% of the mutants successfully survive to adulthood. In these survivors, the brain develops normally, but in males, there is degeneration of spermatogonia resulting in the virtual absence of sperm. Thus, cytochrome c-mediated apoptosis is not absolutely required for normal neural development, but is essential for spermatogenesis. These findings strongly suggest that alternative apoptotic pathways work in conjunction with and parallel to Apaf-1 and can modify its effect on programmed cell death.

Induction of interleukin-12/p40 by superantigens in macrophages is mediated by activation of nuclear factor-kappaB

Multimerization of the MHC class II molecule by superantigens results in activation of cellular signal transduction pathways in macrophage and B cells. Here we show that superantigen staphylococcal enterotoxin B (SEB) induces IL-12/p40 secretion in macrophages. SEB-induced expression of the IL-12/p40 gene involves activation and nuclear translocation of nuclear factor kappaB (NF-kappaB). The NF-kappaB heterodimer bound to the NF-kappaB consensus sequence of the IL-12/p40 gene promoter is p50/C-Rel. Inhibition of PKC and PKA activation results in suppression of activation and translocation of NF-kappaB. We conclude that signals for IL-12/p40 gene transcription from MHC class II molecules follow activation of PKC and PKA, which in turn leads to the activation and translocation of NF-kappaB to the nucleus. Our study suggests that superantigens are capable of influencing the nature of the immune response by regulating cytokine production. Induction of IL-12 production by superantigens may therefore play a role in the regulation of Th 1-mediated immune response and autoimmune disease.

[Study on expression of disaccharide residue and its significance in lung cancer tissues.]

BACKGROUND

To study the expression of disaccharide residu (D-Galactose-beta-(1v3)-N-Acetyl- galactosamine) in lung cancer.

METHODS

Surgical dissected samples from 109 cases of lung cancer and 87 cases of lung benign diseases were fixed in 4 % formaldehyde and embeded in parafin. Disaccharide residue was examined by galactose oxidase-Schiff's method.

RESULTS

The positive rate of bronchial submucous glands from patients with lung cancer was 71. 76 %(61/ 85) , and the positive rate of bronchial submucous gland from patients with benign pulmonary diseases was 71. 83 %(51/ 71) . There was no significant difference between two groups (Chi-Square = 0. 0026 , P > 0. 9) . Among 94 cases of lung cancer tissues , the positive rate of adenocarcinoma was 36. 11 %(13/ 36) , and the other lung cancer were negative reaction.

CONCLUSIONS

The study showed that disaccharide residue was expressed in submucous glands of bronchial submuca in both patients with pulmonary benign or malignant diseases , and only expressed in partial adenocarcinoma tissues among the pulmonary carcinoma. It has not enough evidence to differentiate benign from malignant diseases of lung.

[Detection of RB1 mutations by using quantitative fluorescent mutiplex PCR]

OBJECTIVE

To develop a half-automatic, simple, non-radioactive technique for rapid detection of mutation in the RB gene.

METHODS

Quantitative fluorescent multiplex PCR (QFM-PCR) involves amplification of the promoter region and all 27 exons of the RB1 gene with fluorescein labeled primers in multiplex sets. Primers were divided into multiplex sets of three to seven pairs of primers, also contained were internal control primers C4. Four external controls were also tested by using nullisomic, monosomic, diploid, and trisomic for RB1. The number of copies of a fragment in a test sample was calculated by comparing fluorescence intensity of the fragment with these standards. Fragment value detection and subsequent calculations were performed automatically by Fragment Manager 2.1 Software.

RESULTS

Small deletions, insertions and whole exon deletion in the RB1 gene were detected from genomic DNA. Sequencing analysis and RB tumor homozygous mutation comfirmed the defects detected by QFM-PCR.

CONCLUSION

The approach is a rapid, cost-effective initial method for screening patient samples. It has been used to identify approximately 50% positives of tested samples. The mutations shown were not only small deletion and insertion, but also the single copy exons heterozygous mutation in the RB1 gene which the previously used methods were unable to detect. These features make the technique an attractive approach to clinical diagnosis of gene defects.

[Detection of R277Q mutation of SRD5alpha2 gene by amplification refractory mutation system]

OBJECTIVE

To set up a simple method for identifying the mutation of R227Q of SRD5alpha2 gene which is one of the most common mutations in congenital hypospadias in China.

METHODS

The amplification refractory mutation system(ARMS) was employed in detecting the SRD5alpha2 gene R227Q mutation in congenital hypospadias confirmed by PCR-SSCP and DNA sequencing.

RESULTS

The ARMS was successfully applied to the detection of the R227Q mutation of SRD5alpha2 gene. Three out of 23 congenital hypospadias were positive for R227Q mutation. The mutations determined by ARMS were in full agreement with those obtained by the DNA sequencing.

CONCLUSION

This is a simple, rapid and accurate method. It can be used for detecting the SRD5alpha2 gene R227Q mutation in congenital hypospadias and male pseudohermaphroditism.

[Study on G487A mutation of the glucose-6-phosphate dehydrogenase gene]

OBJECTIVE

In order to reveal the molecular evolution and ethnic origin and immigration, on the basis of G6PD G487A mutation, and estimate the incidence of the mutation in Bai, Dai, and Han people in Yunnan and Guangxi.

METHOD

G6PD deficient individuals were studied by using PCR-RE, PCR-SSCP and DNA sequencing.

RESULTS

The G487A mutation in Bai and Dai people was identified for the first time and its relative incidences were 6/66 and 1/52, respectively. The individuals of G6PD G487A mutation showed the features of G6PD clinic type III. No G487A was found in Han people in Guangxi(0/46).

CONCLUSION

The G6PD G487A mutation revealed in some ethnic groups of China implies that different national minorities of Chinese may be origined from a common ancestor.

Overexpression of wild-type retinoic acid receptor alpha (RARalpha) recapitulates retinoic acid-sensitive transformation of primary myeloid progenitors by acute promyelocytic leukemia RARalpha-fusion genes

Retinoic acid receptor alpha (RARalpha) is the target of several chromosomal translocations associated with acute promyelocytic leukemias (APLs). These rearrangements fuse RARalpha to different partner genes creating the chimeric proteins: PML-RARalpha, PLZF-RARalpha, and NPM-RARalpha. Although the vast majority of APLs respond to retinoic acid therapy, those associated with PLZF-RARalpha are resistant. We have used retroviruses to express PML-RARalpha, PLZF-RARalpha, NPM-RARalpha, RARalpha403 (a dominant negative mutant of RARalpha), and wild-type RARalpha in murine bone marrow progenitors and found that all of these constructs blocked differentiation and led to the immortalization of myeloid progenitors. This cellular transformation is specific to an alteration of the RARalpha pathway because overexpression of RARbeta, RARgamma, or RXRalpha did not result in similar growth perturbations. Pharmacological doses of RA induced differentiation and inhibited proliferation of cells transformed with either of the APL fusion genes, including PLZF-RARalpha, whereas physiological retinoic acid concentrations were sufficient to reverse the phenotype of cells transformed with wild-type RARalpha. The cellular responses to retinoic acid were accompanied by a sharp decrease in the amount of the RARalpha-fusion proteins expressed in the cells. Our findings suggest that the oncogenicity of RARalpha-fusion proteins results from their nature to behave as unliganded RARalpha in the presence of physiological concentrations of retinoic acid.

[Molecular characterization of glucose-6-phosphate dehydrogenase variants in four ethnic groups in Yunnan province of China]

OBJECTIVE

In order to understand the molecular evolution, race origin and the relationship between the G6PD gene structure and clinical symptoms, the authors identified the molecular characterization of glucose-6-phosphate dehydrogenase and determined the G6PD gene frequency in four ethnic groups in Yunnan province of China.

METHODS

The point mutations of G6PD were detected by Mismatch-PCR/RE, SSCP,ARMS,DNA sequence and so on. G6PD gene frequency was determined by Hardy-Weinberg Law.

RESULTS

G6PD G1388A, G1376T,A95G mutations were determined in Bai and Dai people for the first time and G1388A also in Harni people by DNA sequence. G6PD C1024T were detected in Dai population by Mismatch-PCR/RE. The gene frequency of G6PD in Bai population in Dali city is 0.0113, and the incidence is 1.19% which are different from those in Dai population.

CONCLUSION

G6PD G1388A,G1376T, A95G and C1024T are the mutations in national minorities as well as in the Han people. The results suggest that different national minorities of China may have the same ancestor. The incidence of G6PD deficiency and the G6PD gene frequency in Bai population are different from those in Dai population. The distribution of G6PD deficiency in Yunnan is associated with the distribution of malaria epidemic in that province.

Tyrphostin B42 inhibits IL-12-induced tyrosine phosphorylation and activation of Janus kinase-2 and prevents experimental allergic encephalomyelitis

IL-12 is a macrophage-derived cytokine that induces proliferation, cytokine production, and cytotoxic activity of T and NK cells. Signaling through its receptor, IL-12 induces these cellular responses by tyrosine phosphorylation and activation of Janus kinase-2 (Jak-2), Tyk-2, Stat3, and Stat4. We have used tyrphostin B42 (AG490), a Jak-2 inhibitor, to determine the role of Jak-2 kinase in IL-12 signaling and IL-12-induced T cell functions. Treatment of activated T cells with tyrphostin B42 inhibited the IL-12-induced tyrosine phosphorylation and activation of Jak-2 without affecting Tyk-2 kinase. In contrast, treatment with tyrphostin A1 inhibited the tyrosine phosphorylation of Tyk-2 but not that of Jak-2 kinase. Inhibition of either Jak-2 or Tyk-2 leads to a decrease in the IL-12-induced tyrosine phosphorylation of Stat3, but not of Stat4, protein. While inhibition of Jak-2 lead to programmed cell death, the inhibition of Jak-2 or Tyk-2 resulted a decrease in IFN-gamma production. We have further tested the in vivo effects of tyrphostin B42 in experimental allergic encephalomyelitis, a Th1 cell-mediated autoimmune disease. In vivo treatment with tyrphostin B42 decreased the proliferation and IFN-gamma production of neural Ag-specific T cells. Treatment of mice with tyrphostin B42 also reduced the incidence and severity of active and passive EAE. These results suggest that tyrphostin B42 prevents EAE by inhibiting IL-12 signaling and IL-12-mediated Th1 differentiation in vivo.

Conservation of cys-cys trp structural triads and their geometry in the protein domains of immunoglobulin superfamily members

In almost all members of the immunoglobulin superfamily (IgSF) for which an experimental structure has been determined, a triad (C-CW) consisting of two cysteine residues that form a disulfide bond and a neighboring tryptophan can be found in the core of the protein fold. We analyzed the geometry of these C-CW triads among a database of 60 Fab crystal structures and found it to be remarkably conserved. We identified C-CW triads of a similar configuration in other members of the IgSF such as T cell receptor (TCR), major histocompatibility complex antigens (MHC), cell surface antigens CD4 and CD8, and cell-adhesion molecules. We used this C-CW pattern to search a database of non-IgSF proteins, and identified several proteins that contain a disulfide bridge associated with a tryptophan in a similar configuration. Examination of the distances and orientations between triads found in adjacent domains in Fab fragments and TCR also reveal a high degree of conservation, which reflects the invariance of the inter-chain domain packing. This high degree of conservation of the geometry of the C-CW triad in IgSF structures suggests that the Trp may contribute significantly to the stability of the disulfide bond. Knowledge of these geometric parameters may prove useful in the construction and validation of theoretical models of Ig, TCR, and other IgSF members.

[Studies on a G6PD polymorphic site, cDNA C1311T]

OBJECTIVE

To use amplification refractory mutation system(ARMS) method to detect the G6PD cDNA C1311T mutation, estimate its frequency in a normal south Chinese population, and investigate whether IVS-11 C93T mutation is the cause of certain G6PD deficient cases.

METHODS

DNA sequencing was used to confirm the C1311T and the IVS-11 C93T mutations. ARMS was set up to detect the C1311T and to estimate its frequency.

RESULTS

Three cases of C1311T mutation were found in 40 G6PD deficient samples. The optimal condition for ARMS was established. Using this method, 19 cases of C1311T were detected in 103 normal men, and the frequency of this polymorphic mutation was estimated to be 18.4% in southern Chinese population. Four cases with G6PD deficiency were demonstrated to be C at the IVS-11 93 position. At the same time, a case of IVS-11 93 C-->T was found in a normal man.

CONCLUSIONS

ARMS is a simple, time-saving, and reliable method for detecting known G6PD gene point mutation. The frequency of C1311T in a normal south Chinese population is 18.4%. IVS-11 C93T might be another polymorphic site of the G6PD gene, and it is not the cause of enzyme deficiency in certain G6PD deficient cases.

[Detection of three common G6PD gene point mutations in Guangdong province by using ARMS]

OBJECTIVE

To detect three common G6PD gene point mutations, G1388A, G1376T and A95G, in Guangdong province and to estimate the approximate frequencies.

METHODS

Using the amplification refractory mutation system(ARMS) method to detect G1388A and G1376T and the newly developed ARMS to identify A95G mutation.

RESULTS

Ninety cases of G6PD deficient male were examined, and 42 of them were identified to be G1388A(46.7%), 14 G1376T(15.6%), and 12 A95G(13.3%). Totally 68 out of the 90 cases(75.6%) were of the three common mutations. The rest belong to rare or undefined mutations.

CONCLUSION

ARMS method can be used in detecting common mutations of G6PD gene with the benefits of simple, fast, economic, and accurate.

Three-dimensional nano-HAp/collagen matrix loading with osteogenic cells in organ culture

Transplantation of osteogenic cells with a suitable matrix is one strategy for engineering bone tissue. Three-dimensional distribution and growth of cells within the porous scaffold are of clinical significance for the repair of large bony defects. A nano-HAp/collagen (nHAC) composite that mimics the natural bone both in composition and microstructure to some extent was employed as a matrix for the tissue engineering of bone. A porous nHAC composite was produced in sheet form and convolved to be a three-dimensional scaffold. Using organ culture techniques and the convolving method, we have developed three-dimensional osteogenic cells/nHAC constructs in vitro. Scanning electron microscopic and histological examination has demonstrated the development of the cells/material complex. Spindle-shaped cells migrating out of bone fragments continuously proliferated and migrated throughout the network of the coil. The porous nHAC scaffold provided a microenvironment resembling that seen in vivo, and cells within the composite eventually acquired a tridimensional polygonal shape. In addition, new bone matrix was synthesized at the interface of bone fragments and the composite.

[A study of load stress on an implant and a tooth supported fixed bridge for the first mandibular molar]

OBJECTIVE AND METHODS

A study of load stress on an implant and a tooth supported fixed bridge for the first mandibular molar was performed by means of 3-D FEA in order to reveal the displacement and stress distribution.

RESULTS

The results show that the maximum displacement of the second premolar is greater than that of the terminal implant, but there is no difference between the mean (mean) under dispersed load statistically, due to the framework function of the bridge. The stress concentration appears around the neck of the abutments, on the contrary, a little stress is found around the apical portion of the second premolar. When the load concentrates on-to the abutments, the displacement and stress value increase obviously.

CONCLUSION

The attention should be paid to the load and occlusion of the terminal implant. This kind of bridge design may be used in clinical practice.