Structural and mutational characterization of -carnitine binding to human carnitine acetyltransferase

We report the crystal structure of a binary complex of human peroxisomal carnitine acetyltransferase and the substrate l-carnitine, refined to a resolution of 1.8 Angstrom with an R(factor) value of 18.9% (R(free)=22.3%). L-carnitine binds to a preformed pocket in the active site tunnel of carnitine acetyltransferase aligned with His(322). The quaternary nitrogen of carnitine forms a pi-cation interaction with Phe(545), while Arg(497) forms an electrostatic interaction with the negatively charged carboxylate group. An extensive hydrogen bond network also occurs between the carboxylate group and Tyr(431), Thr(444), and a bound water molecule. Site-directed mutagenesis and kinetic characterization reveals that Tyr(431), Thr(444), Arg(497), and Phe(545) are essential for high affinity binding of L-carnitine.     

Casein kinase 1alpha interacts with RIP1 and regulates NF-kappaB activation

Tumor necrosis factor alpha (TNFalpha) triggers a signaling pathway converging on the activation of NF-kappaB, which forms the basis for many physiological and pathological processes. In a kinase gene screen using a NF-kappaB reporter, we observed that overexpression of casein kinase 1alpha (CK1alpha) enhanced TNFalpha-induced NF-kappaB activation, and a CK1alpha kinase dead mutant, CK1alpha (K46A), reduced NF-kappaB activation induced by TNFalpha. We subsequently demonstrated that CK1alpha interacted with receptor interacting protein 1 (RIP1) but not with TRADD, TRAF2, MEKK3, IKKalpha, IKKbeta, or IKKgamma in mammalian cells. RIP1 is an indispensable molecule in TNFalpha/NF-kappaB signaling. We demonstrated that CK1alpha interacted with and phosphorylated RIP1 at the intermediate domain. Finally, we showed that CK1alpha enhanced RIP1-mediated NF-kappaB activation. Taken together, our studies suggest that CK1alpha is another kinase that regulates RIP1 function in NF-kappaB activation.     

Computational analysis and prediction for exons of PAC579 genomic sequence

To isolate the novel genes related to human hepatocellular carcinoma (HCC), we se-quenced P1-derived artificial chromosome PAC579 (D17S926 locus) mapped in the minimum LOH (loss of heterozygosity) deletion region of chromosome 17p13.3 in HCC. Four novel genes mapped in this genomic sequence area were isolated and cloned by wet-lab experiments, and the exons of these genes were located. 0-60 kb of this genomic sequence including the genes of interest was scanned with five different computational exon prediction programs as well as four splice site recognition programs. After analyzing and comparing the computationally predicted results with the wet-lab experiment results, some potential exons were predicted in the genomic sequence by using these programs.     

Effects of human eosinophil granule-derived cationic proteins on C-fiber afferents in the rat lung.

Experiments were performed to test the hypothesis that human eosinophil granule-derived cationic proteins stimulate vagal C-fiber afferents in the lungs and elicit pulmonary chemoreflex responses in anesthetized Sprague-Dawley rats. Intratracheal instillation of eosinophil cationic protein (ECP; 1-2 mg/ml, 0.1 ml) consistently induced an irregular breathing pattern, characterized by tachypnea (change in breathing frequency of 44.7%) and small unstable tidal volume (VT). The tachypnea, accompanied by decreased heart rate and arterial blood pressure, started within 30 s after the delivery of ECP and lasted for >30 min. These ECP-induced cardiorespiratory responses were completely prevented by perineural capsaicin treatment of both cervical vagi, which selectively blocked C-fiber conduction, suggesting the involvement of these afferents. Indeed, direct recording of single-unit activities of pulmonary C-fibers further demonstrated that the same dose of ECP evoked a pronounced and sustained (>30-min) stimulatory effect on pulmonary C-fibers. Furthermore, the sensitivity of these afferents to lung inflation was also markedly elevated after the ECP instillation, whereas the vehicle of ECP administered in the same manner had no effect. Other types of eosinophil granule cationic proteins, such as major basic protein and eosinophil peroxidase, induced very similar respiratory and cardiovascular reflex responses. In conclusion, these results show that eosinophil granule-derived cationic proteins induce a distinct stimulatory effect on vagal pulmonary C-fiber endings, which may play an important role in the airway hyperresponsiveness associated with eosinophil infiltration in the airways.     

神经生长因子家族成员NGF、BDNF、NT-3和NT-4在猫L6脊髓的分布

采用免疫组织化学方法观察神经生长因子家庭成员NGF,BDNF、NT3和NT4在成年猫L6脊髓的分布。结果;在L6脊髓灰质均可见四种生长因子的免疫阳性细胞,这些细胞主要是腹角及凝角深部的大神经元及背角浅层的小神经元,灰质内亦内NGF,NT3及NT4阳性的胶质细胞,但数量多少不等,其中NT3者最多,其次是NGF,NT4者最少,此外,Ⅱ板层内还可见较多BDNF及少量NT-3阳性神经膨体,本文结果表明,在成年猫脊髓存在NGF,BDNF、NT3和NT4,但其分布有差异。     

Inhibition of protein-tyrosine phosphatase stimulates the dynamin-dependent endocytosis of ROMK1.

We have previously shown that inhibiting protein-tyrosine kinase increased whereas inhibiting protein-tyrosine phosphatase (PTP) decreased renal outer medullary potassium channel 1 (ROMK1) channel activity (1). We have now used confocal microscopy, the patch clamp technique, and biotin labeling to further examine the role of tyrosine phosphorylation in regulating ROMK1 trafficking. Human embryonic kidney 293 cells were cotransfected with c-Src and green fluorescent protein-ROMK1, which has the same biophysical properties as those of ROMK1. Patch clamp studies have shown that phenylarsine oxide (PAO), an inhibitor of PTP, decreased the activity of ROMK1. Moreover, addition of PAO reduced the cell surface localization of green fluorescent protein-ROMK1 detected by confocal microscopy and diminished the surface ROMK1 density by 65% measured by biotin labeling. Also, PAO treatment significantly increased the phosphorylation of ROMK1. The notion that the effect of PAO is mediated by stimulating tyrosine phosphorylation-induced endocytosis of ROMK1 has also been supported by findings that mutating the tyrosine residue 337 of ROMK1 to alanine abolished the effect of PAO. Finally, the inhibitory effect of PAO on ROMK1 was completely blocked in the cells co-transfected with dominant negative dynamin (dynaminK44A). This indicates that the tyrosine phosphorylation-induced endocytosis of ROMK1 is dynamin-dependent. We conclude that inhibiting PTP increases ROMK1 phosphorylation and results in a dynamin-dependent internalization of the channel.     

Human MutY homolog, a DNA glycosylase involved in base excision repair, physically and functionally interacts with mismatch repair proteins human MutS homolog 2/human MutS homolog 6.

Adenines mismatched with guanines or 7,8-dihydro-8-oxo-deoxyguanines that arise through DNA replication errors can be repaired by either base excision repair or mismatch repair. The human MutY homolog (hMYH), a DNA glycosylase, removes adenines from these mismatches. Human MutS homologs, hMSH2/hMSH6 (hMutSalpha), bind to the mismatches and initiate the repair on the daughter DNA strands. Human MYH is physically associated with hMSH2/hMSH6 via the hMSH6 subunit. The interaction of hMutSalpha and hMYH is not observed in several mismatch repair-defective cell lines. The hMutSalpha binding site is mapped to amino acid residues 232-254 of hMYH, a region conserved in the MutY family. Moreover, the binding and glycosylase activities of hMYH with an A/7,8-dihydro-8-oxo-deoxyguanine mismatch are enhanced by hMutSalpha. These results suggest that protein-protein interactions may be a means by which hMYH repair and mismatch repair cooperate in reducing replicative errors caused by oxidized bases.     

Exercise training normalizes altered calcium-handling proteins during development of heart failure.

The cardiac sarcoplasmic reticulum calcium-ATPase (SERCA2a), Na+/Ca2+ exchanger (NCX1), and ryanodine receptor (RyR2) are proteins involved in the regulation of myocyte calcium. We tested whether exercise training (ET) alters those proteins during development of chronic heart failure (CHF). Ten dogs were chronically instrumented to permit hemodynamic measurements. Five dogs underwent 4 wk of cardiac pacing (210 beats/min for 3 wk and 240 beats/min for the 4th wk), whereas five dogs underwent the same pacing regimen plus daily ET (5.1 +/- 0.3 km/h, 2 h/day). Paced animals developed CHF characterized by hemodynamic abnormalities and reduced ejection fraction. ET preserved resting hemodynamics and ejection fraction. Left ventricular samples were obtained from all dogs and another five normal dogs for mRNA (Northern analysis, band intensities normalized to glyceraldehyde-3-phosphate dehydrogenase) and protein level (Western analysis, band intensities normalized to tubulin) measurements. In failing hearts, SERCA2a was decreased by 33% (P < 0.05) and 65% (P < 0.05) in mRNA and protein level, respectively, compared with normal hearts; there was only an 8.6% reduction in mRNA and a 32% reduction in protein in exercised animals (P < 0.05 from CHF). mRNA expression of NCX1 increased by 44% in paced-only dogs compared with normal (P < 0.05) but only by 22% in trained dogs (P < 0.05 vs. CHF); protein level of NCX1 was elevated in paced-only dogs (71%, P < 0.05) but partially normalized by ET (33%, P < 0.05 from CHF). RyR2 was not altered in any of the dogs. In conclusion, long-term ET may ameliorate cardiac deterioration during development of CHF, in part via normalization of myocardial calcium-handling proteins.     

Ginseng berry reduces blood glucose and body weight in db/db mice.

In this study, we observed anti-diabetic and anti-obesity effects of Panax ginseng berry in adult C57BL/Ks db/db mice and their lean littermates. Animals received daily intraperitoneal injections of Panax ginseng berry extract at 150 mg/kg body wt. for 12 consecutive days. On Day 5, the extract-treated db/db mice had significantly lower fasting blood glucose levels as compared to vehicle-treated mice (180.5+/-10.2 mg/dl vs. 226.0+/-15.3 mg/dl, P < 0.01). On day 12, the extract-treated db/db mice were normoglycemic (134.3+/-7.3 mg/dl) as compared to vehicle-treated mice (254.8+/-24.1 mg/dl; P < 0.01). Fasting blood glucose levels of lean mice did not decrease significantly after treatment with extract. After 12 days of treatment with the extract, glucose tolerance increased significantly, and overall blood glucose exposure calculated as area under the curve (AUC) decreased 53.4% (P < 0.01) in db/db mice. Furthermore, db/db mice treated with extract (150 mg/kg body wt.) showed weight loss from 51.0+/-1.9 g on Day 0, to 46.6+/-1.7 g on Day 5, and to 45.2+/-1.4 g on Day 12 (P < 0.05 and P < 0.01 compared to Day 0, respectively). The body weight of lean littermates also decreased at the same dose of extract. These data suggest that Panax ginseng berry extract may have therapeutic value in treating diabetic and obese patients.     

Effects of seasoning and heating device on mutagenicity and heterocyclic amines in cooked beef.

Pan-roasted beef showed a lower mutagenicity after various degrees of cooking than charcoaled one. The high mutagenicity of charcoaled beef was due to the formation of more heterocyclic amines, especially AalphaC (2-amino-9H-pyrido- [2,3-b]indole) and PhIP (2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine) because of rapid and direct heating on the surface of the meat at a high temperature. Seasoning decreased mutagenicity of pan-roasted beef except the very well done sample with unchanged heterocyclic amine contents, but increased mutagenicity of charcoaled beef with decreased levels of AalphaC and PhIP, probably due to the change of heterocyclic amine precursors or alternatively to the occurrence of other mutagens.