Association of the missense variant p.Arg203Trp in PACS1 as a cause of intellectual disability and seizures.

Graphical abstract key: ADHD, attention deficit hyperactivity disorder; ASD, atrial septal defect; DD, developmental delay; EEG, electroencephalogram; Ht, height; ID, intellectual disability; OCD, obsessive-compulsive disorder; OFC, open fontanelle; PDA, patent ductus arteriosis; PFO, patent foramen ovale; VSD, ventricular septal defect; Wt, weight.

Post-transcriptional regulation controlled by E-cadherin is important for c-Jun activity in melanoma.

A central event in the development of malignant melanoma is the loss of the tumor-suppressor protein E-cadherin. Here, we report that this loss is linked to the activation of the proto-oncogene c-Jun, a key player in tumorigenesis. In vivo, malignant melanomas show strong expression of the c-Jun protein in contrast to melanocytes. Interestingly, c-Jun mRNA levels did not differ in the melanoma cell lines when compared to melanocytes, suggesting that c-Jun could be regulated at the post-transcriptional level. To uncover the link between E-cadherin and c-Jun, we re-expressed E-cadherin in melanoma cells and detected decreased protein expression and activity of c-Jun. Furthermore, c-Jun accumulation is dependent on active E-cadherin-mediated cell-cell adhesion and regulated via the cytoskeleton. Additionally, we determined that, with respect to c-Jun regulation, there are two melanoma subgroups. One subgroup regulates c-Jun expression via the newly discovered E-cadherin-dependent signaling pathway, whereas the other subgroup uses the MAPKinases to regulate its expression. In summary, our data provide novel insights into the tumor-suppressor function of E-cadherin, which contributes to the suppression of c-Jun protein translation and transcriptional activity independent of MAPKinases.

Cleft width and secondary alveolar bone graft success.

Fifty-six cleft sites were reviewed prior to alveolar bone grafting and subsequently evaluated for graft success using study models, periapical and occlusal radiographs from the Lancaster Cleft Palate Clinic. All patients in this sample had presurgical orthodontics to expand and align the maxillary arch prior to alveolar bone grafting. Ninety-five percent of the grafts were done using iliac crest, the remaining 5% were cranial grafts. The alveolar bone grafting technique used was as described by Boyne and Sands (1972, 1976). Cleft width was measured on a radiograph taken no more than 1 month preoperatively, following the completion of all orthodontic expansion. Cleft width was determined by inspection at its narrowest point. A distortion correction was attempted by determining the ratio of the radiographic width of the maxillary central incisor adjacent to the cleft compared with the actual width of this tooth measured on study models. The radiographic cleft width was then multiplied by this factor to approximate true cleft width. Alveolar contour was measured at least 6 months postoperatively using ratios of actual bone heights measured at the mesial, middle, and distal margin of the previous cleft compared with root length of adjacent teeth. This was to eliminate the radiographic distortion factors of foreshortening and elongation. Regression analysis was carried out to see if there was a correlation between preoperative cleft width and eventual success of the graft as measured on postsurgical radiographs. The success rate for achieving a bony bridge across the cleft was 91%.(ABSTRACT TRUNCATED AT 250 WORDS)

The three-dimensional crystal structure of cholera toxin.

The clinical manifestations of cholera are largely attributable to the actions of a secreted hexameric AB5 enterotoxin (choleragen). We have independently solved and refined the three-dimensional structure of choleragen at 2.5 A resolution. The structure of the crystalline toxin closely resembles that described for the heat-labile enterotoxin from Escherichia coli (LT) with which it shares 80% sequence homology. In both cases, the wedge-shaped A subunit is loosely held high above the plane of the pentameric B subunits by the tethering A2 chain. The most striking difference between the two toxins occurs at the carboxyl terminus of the A2 chain. Whereas the last 14 residues of the A2 chain of LT threading through the central pore of the B5 assembly form an extended chain with a terminal loop, the A2 chain of choleragen remains a nearly continuous alpha-helix throughout its length. The four carboxyl-terminal residues of the A2 chain (KDEL sequence), disordered in the crystal structure of LT, are clearly visible in choleragen's electron-density map. In the accompanying article we describe the three-dimensional structure of the isolated B pentamer of cholera toxin (choleragenoid). Comparison of the crystalline coordinates of choleragen, choleragenoid, and LT provides a solid three-dimensional foundation for further experimental investigation. These structures, along with those of related toxins from Shigella dysenteria and Bordetella pertussis, offer a first step towards the rational design of new vaccines and anti-microbial agents.

Hydrophobic binding of pertussis toxin is enhanced by oligosaccharide receptors.

Pertussis toxin is one of several virulence factors produced by Bordetella pertussis, the etiologic agent of whooping cough. Pertussis toxin is an oligomeric A-B class toxin composed of an ADP-ribosyltransferase S1 (A) subunit and a B oligomer containing lectin-like binding domains. The carbohydrate binding specificity of the B oligomer is for sialooligosaccharide sequences expressed on target cell receptors and asparagine-linked glycans found in many serum glycoproteins. Pertussis toxin also has the ability to bind to the inert surfaces of culture tubes. In this report we present data showing that pertussis toxin binding to polypropylene microcentrifuge tubes was enhanced in a time- and concentration-dependent manner by the addition of soluble glycoprotein or oligosaccharide receptor analogs. Evidence obtained using the hydrophilic and hydrophobic surfaces of Gel Bond electrophoresis casting film indicated that receptor-enhanced binding was likely due to hydrophobic interactions. Hydrophobic binding of the isolated B oligomer of pertussis toxin was enhanced only in the presence of high concentrations of glycoproteins. Therefore, the S1 (A) subunit of pertussis holotoxin appears to play a role in receptor-enhanced hydrophobic binding. We propose, therefore, that pertussis toxin binding to its receptors may expose or preferentially orient hydrophobic residues that may contribute to the functional association of the toxin with host cell plasma membranes and delivery of the S1 subunit to its intracellular target.

Structure and function of cholera toxin and the related Escherichia coli heat-labile enterotoxin.

Cholera and the related Escherichia coli-associated diarrheal disease are important problems confronting Third World nations and any area where water supplies can become contaminated. The disease is extremely debilitating and may be fatal in the absence of treatment. Symptoms are caused by the action of cholera toxin, secreted by the bacterium Vibrio cholerae, or by a closely related heat-labile enterotoxin, produced by Escherichia coli, that causes a milder, more common traveler's diarrhea. Both toxins bind receptors in intestinal epithelial cells and insert an enzymatic subunit that modifies a G protein associated with the adenylate cyclase complex. The consequent stimulated production of cyclic AMP, or other factors such as increased synthesis of prostaglandins by intoxicated cells, initiates a metabolic cascade that results in the excessive secretion of fluid and electrolytes characteristic of the disease. The toxins have a very high degree of structural and functional homology and may be evolutionarily related. Several effective new vaccine formulations have been developed and tested, and a growing family of endogenous cofactors is being discovered in eukaryotic cells. The recent elucidation of the three-dimensional structure of the heat-labile enterotoxin has provided an opportunity to examine and compare the correlations between structure and function of the two toxins. This information may improve our understanding of the disease process itself, as well as illuminate the role of the toxin in studies of signal transduction and G-protein function.

Binding to native proteins by antipeptide monoclonal antibodies.

mAb raised against synthetic peptides derived from cholera toxin, myohemerythrin, and sickle hemoglobin were analyzed by both solid-phase and solution-phase methods. Antipeptide mAb against cholera toxin (mAb TE32 and TE33), against myohemerythrin (mAb B13I2, B13C2, and B13F2), and against sickle hemoglobin (mAb HuS-1 and HuS-2), had been previously described and used for vaccine development, structural characterization, or identification of a specific antigenic determinant, and each was apparently capable of binding both peptide and native Ag. In this study, all were found to bind whole protein when tested against immobilized Ag in a standard solid-phase assay (ELISA), yet none of the antibodies recognized the Ag in its true native form, failing to bind when tested in several solution-phase assay systems, including size exclusion HPLC. This discrepancy may be the result of modifications of the epitope created by interaction and possible denaturation of the protein on the solid-phase matrix. As a consequence, binding of these antibodies to peptides, either immobilized or in solution, or to immobilized protein, cannot be used to infer that the peptide has assumed a conformation that corresponds to that of the cognate sequence in the native protein. A re-evaluation of binding data that relates antipeptide mAb to native structural characteristics may be necessary.

Crystallization of isoelectrically homogeneous cholera toxin.

Past difficulty in growing good crystals of cholera toxin has prevented the study of the crystal structure of this important protein. We have determined that failure of cholera toxin to crystallize well has been due to its heterogeneity. We have now succeeded in overcoming the problem by isolating a single isoelectric variant of this oligomeric protein (one A subunit and five B subunits). Cholera toxin purified by our procedure readily forms large single crystals. The crystal form (space group P2(1), a = 73.0 A, b = 92.2 A, c = 60.6 A, beta = 106.4 degrees, one molecule in the asymmetric unit) has been described previously [Sigler et al. (1977) Science (Washington, D.C.) 197, 1277-1278]. We have recorded data from native crystals of cholera toxin to 3.0-A resolution with our electronic area detectors. With these data, we have found the orientation of a 5-fold symmetry axis within these crystals, perpendicular to the screw dyad of the crystal. We are now determining the crystal structure of cholera toxin by a combination of multiple heavy-atom isomorphous replacement and density modification techniques, making use of rotational 5-fold averaging of the B subunits.

Cytochrome c peroxidase compound I: formation of covalent protein crosslinks during the endogenous reduction of the active site.

Cytochrome c peroxidase (ferrocytochrome-c:hydrogen-peroxide oxidoreductase, EC 1.11.1.5) was oxidized by hydrogen peroxide in the absence of exogenous electron donor. Higher molecular weight species were observed in the decay products at pH 4.5. Monomer and dimer were separated by gel filtration and purified by anion-exchange chromatography. Peptide mapping of tryptic digests of the dimer indicated a tyrosine crosslink localized between residues 32 and 48 of the native enzyme.