Biochemical characterization of the structure-specific DNA-binding protein Cmb1 from Schizosaccharomyces pombe.

Cmb1, a novel HMG box protein from Schizosaccharomyces pombe, has been characterized biochemically using glutaraldehyde cross-linking, gel-filtration and analytical ultracentrifugation. It was identified as a monomeric, non-spherical protein, with a tendency to aggregate in solution. Limited proteolysis with trypsin and chymotrypsin showed that the C-terminal HMG box was a compact, proteolytically stable domain and the N-terminal region of Cmb1 was relatively unstructured and more easily digested. As Cmb1 was previously identified as a potential mismatch-binding protein, the binding constants and stoichiometry for both homoduplex and heteroduplex DNA were determined using an IASys resonant mirror biosensor. Cmb1 indeed demonstrated a tighter association with mismatched DNA, especially with the C/Delta-mismatch. Expression constructs of Cmb1 were made to study the sections of the protein involved in DNA binding. Constructs with the N-terminal region absent revealed that the C-terminal HMG box was the primary DNA-binding region. The presence of the N-terminal region did, however, facilitate tighter binding to both homoduplex and heteroduplex DNA. The amino acid residues isoleucine 14 and leucine 39 were located as putative intercalating residues using structure guided homology modelling. The model templates were derived from two distinct HMG:DNA complexes: HMG-D bound to homoduplex DNA and HMG 1 bound to cisplatin DNA. Binding studies using the Cmb1 HMG box with point mutations in these residues showed that isoleucine 14 was important for the binding of Cmb1 to homoduplex DNA, but affected binding to mismatches to a lesser extent. In contrast, leucine 39 appeared to have a more significant function in binding to mismatched DNA.

Therapeutics and prion disease: can immunisation or drugs be effective?

Prion diseases are of considerable importance because of the threat of a variant form of Creutzfeldt Jakob disease that has emerged in recent years. Pre-clinical diagnosis of prion diseases still remains poor and effective therapies also do not exist at present. This review examines research on possible therapeutic strategies that might have potential benefits if applied before neurodegeneration has occurred.

Amyloid beta-peptide and its relationship with dementia in Lewy body disease.

Cerebral cortical Lewy bodies occur in a spectrum of clinical syndromes including Parkinson's disease (PD) with and without dementia, and dementing conditions clinically resembling Alzheimer's disease with few or without parkinsonian features. It is unclear whether these conditions are variants of one disease process or represent pathogenetically distinct entities. Here we compared the cortical pathology in post mortem brains of three groups representing the predominant clinical phenotypes of Lewy body disease, including 27 non-demented cases of PD, 23 demented PD cases, and 11 cases of Lewy body disease who initially presented with dementia and showed only limited features of parkinsonism during the course of their illness. In addition to neuropathology, computer-assisted histoblot analysis was used to assess cortical amyloid beta-peptide deposition. There was wide overlap of the pathomorphometric features between the two groups of demented cases. It appears that substantial cortical Alzheimer-type pathology present in most demented cases contributes significantly to the development of dementia in Lewy body disease.

Altered regulation of cell surface peptidases in human cholesteatoma.

Cholesteatoma is a destructive process involving an accumulation of desquamated keratin arising from squamous epithelium that pathologically has invaded the middle ear or mastoid process. The clinical hallmarks of cholesteatomas, namely invasion of healthy tissues, migration, unrestrained proliferation, aggressiveness, recidivism, and uncoordinated differentiation predict the existence of defects in the normal biology and biochemistry of the cellular constituents that compose a cholesteatoma, as well as in the cellular interactions between these cells, the surrounding normal tissue, and the host. In the current report, we analyzed 11 cholesteatomas and matched healthy tissue for altered expression in four different cell surface peptidases, aminopeptidase A, aminopeptidase N, dipeptidyl peptidase IV, and neutral endopeptidase. We suggest that peptidases may modulate cell growth and differentiation by inactivating stimulatory signals (or conversely, by activating inhibitory signals).

Epidermal inclusion cyst versus thyroglossal duct cyst: sistrunk or not?

Epidermal inclusion cyst (EIC) is a recognized cause of an anterior neck mass in children. Controversy exists as to the proper surgical management of an anterior neck EIC: is simple excision adequate treatment, or is a Sistrunk procedure necessary? A retrospective review of the operative logs of the two senior authors (M.M.A., R.F.W.) from 1993 to the present revealed 16 children, ages 6 months to 9 years (mean, 4.5 years), with a diagnosis of anterior neck EIC. An accurate intraoperative diagnosis of an EIC in all cases allowed for a simple excision of the mass rather than a Sistrunk procedure. The final histologic diagnosis was EIC in all 16 patients. Follow-up of these 16 patients for a mean of 4.5 years revealed no recurrences or complications. When the diagnosis of EIC can be made confidently in the operating room, simple excision is an adequate surgical treatment.

Elevated manganese levels in blood and central nervous system occur before onset of clinical signs in scrapie and bovine spongiform encephalopathy.

Prion diseases, or transmissible spongiform encephalopathies, are neurodegenerative diseases that can only be accurately diagnosed by analysis of central nervous system tissue for the presence of an abnormal isoform of the prion protein known as PrP(Sc). Furthermore, these diseases have long incubation periods during which there are no clear symptoms but where the infectious agent could still be present in the tissues. Therefore, the development of diagnostic assays to detect a surrogate marker for the presence of prion disease is essential. Previous studies on mice experimentally infected with scrapie, an ovine spongiform encephalopathy, suggested that changes in the levels of Mn occur in the blood and brain before the onset of symptoms of the disease. To assess whether these findings have relevance to the animal diseases scrapie and bovine spongiform encephalopathy, tissues from bovine spongiform encephalopathy- and scrapie-infected cattle and sheep were analyzed for their metal content and compared with values for noninfected animals. In field cases and experimentally infected animals, elevated Mn was associated with prion infection. Although some central nervous system regions showed elevated Mn, other regions did not. The most consistent finding was an elevation of Mn in blood. This change was present in experimentally infected animals before the onset of symptoms. In scrapie-infected sheep, elevated Mn levels occurred regardless of the genotype of the sheep and were even detected in scrapie-resistant sheep in which no symptoms of disease were detected. These findings suggest that elevated blood Mn could be a potential diagnostic marker for prion infection even in the absence of apparent clinical disease.

A system of categorizing enzyme-cell wall associations in Agaricus bisporus, using operational criteria.

Enzymes were investigated for their occurrence in the cell wall fraction (4,000 g sediment of the homogenate) of Agaricus bisporus sporocarps. Besides the markers malate dehydrogenase (MalDH), hexokinase (HK) and ATPase, the range of entities studied included gamma-glutamyl transferase (gamma-GT), mannitol dehydrogenase (MDH), phenoloxidase, chitin and beta-1,3-glucan synthases (ChS, beta-GS), chitinase, beta-N-acetylhexosaminidase (HexNAc'ase) and beta-glucanase. Using the extractability in dilute buffer, digitonin and NaCl at high ionic strength as the operational criteria, four categories (I-IV) of enzyme-wall associations could be discerned: category I encompasses enzymes which are artefactually present (i.e. contaminants); category II, enzymes that are hydrophobically bound (which may or may not be genuinely wall-associated), III includes enzymes that are ionically bound and IV, enzymes whose bonding to the wall is in all probability covalent. The same enzyme entity may have representatives in more than one category, e.g. ChS and beta-GS (I, II, IV), phenolase (I, II, III, IV), beta-glucanase, chitinase and HexNAc'ase (I, IV). It is thought that the categorization presented could be of general applicability in fungi as well as in higher plants to specify enzyme-wall associations in a straightforward, comparable manner, thus avoiding some of the ambiguous terms prevailing in the literature, such as "weakly", "strongly" or "tightly" wall bound. The results are discussed in more detail for several of the more economically important enzymes studied.

Mucinous eccrine carcinoma of the eyelid.

A 78-year-old woman with recurrent chalazia of the upper eyelid was found to have mucinous eccrine carcinoma. This rare pathologic entity, with low metastatic potential, nevertheless has a significant recurrence rate. This case underscores the importance of considering this tumor in recalcitrant eyelid lesions and highlights the pathology of this tumor. A summary of previous cases is also presented.

Sclerosing sweat duct carcinoma of the eyelid margin: unusual presentation of a rare tumor.

OBJECTIVE: Sclerosing sweat duct carcinoma (SSDC) is a rare, slow-growing, locally invasive skin tumor of eccrine and pilar origin. It is usually located on the face, particularly the upper lip, cheek, and forehead. It has been infrequently reported on the eyelid, secondarily involved from adjacent cheek and brow tumors. Only four previous cases have reported primary eyelid tumors. The authors present four cases of primary eyelid margin involvement, which show the variability in clinical presentations. DESIGN: Retrospective case series. The authors present four case studies of lower eyelid margin tumors diagnosed as SSDC. PARTICIPANTS/METHODS: The history of this recently recognized neoplasm is discussed in relation to the cases presented and the role of the ophthalmologist and pathologist in such cases. RESULTS: Primary SSDC of the eyelid margin is a reportedly rare entity. This particular presentation can occur in all age groups; can mimic benign, acanthotic, or basal cell-like tumors; and is usually misdiagnosed initially. This can lead to a delay in definitive treatment for a tumor that classically presents late in its natural history to health professionals. All eight cases of primary eyelid SSDC now reported in the literature have occurred in the lower lid. CONCLUSION: This rare but aggressive tumor is difficult to diagnose from a simple biopsy and may be more common than previously believed. Initial or early diagnosis is important because of unusually invasive characteristics. Recurrence is common and usually leads to extensive tissue loss via direct invasion or subsequent wide resection. Correct histologic diagnosis at the time of initial tumor removal will likely aid in achieving complete excision with fewer recurrences.

A novel human tocopherol-associated protein: cloning, in vitro expression, and characterization.

Vitamin E (alpha-tocopherol) is an essential dietary nutrient for humans and animals. The mechanisms involved in cellular regulation as well as in the preferential cellular and tissue accumulation of alpha-tocopherol are not yet well established. We previously reported (Stocker, A., Zimmer, S., Spycher, S. E., and Azzi, A. (1999) IUBMB Life 48, 49-55) the identification of a novel 46-kDa tocopherol-associated protein (TAP) in the cytosol of bovine liver. Here, we describe the identification, the molecular cloning into Escherichia coli, and the in vitro expression of the human homologue of bovine TAP, hTAP. This protein appears to belong to a family of hydrophobic ligand binding proteins, which have the CRAL (cis-retinal binding motif) sequence in common. By using a biotinylated alpha-tocopherol derivative and the IASys resonant mirror biosensor, the purified recombinant protein was shown to bind tocopherol at a specific binding site with K(d) 4.6 x 10(-7) m. Northern analyses showed that hTAP mRNA has a size of approximately 2800 base pairs and is ubiquitously expressed. The highest amounts of hTAP message are found in liver, brain, and prostate. In conclusion, hTAP has sequence homology to proteins containing the CRAL_TRIO structural motif. TAP binds to alpha-tocopherol and biotinylated tocopherol, suggesting the existence of a hydrophobic pocket, possibly analogous to that of SEC14.

Increased numbers of mast cells in human middle ear cholesteatomas: implications for treatment.

HYPOTHESIS: Because many of the biologic phenomena in which mast cells are involved also are observed in human cholesteatoma pathology, the authors hypothesized that mast cells may play a role in this disease. The first test of this hypothesis is to determine whether there are an increased number of mast cells associated with cholesteatomas. BACKGROUND: The molecular and cellular defects that result in the pathologic features observed in acquired and congenital cholesteatomas are unknown. One common feature of cholesteatoma pathogenesis is the presence of bacteria and a numerous inflammatory cytokines expressed by host inflammatory cells. The interactions between inflammatory cells and cholesteatoma epithelium could result in the induction of other aberrant biologic features of cholesteatomas. Thus, it is critical to the understanding of the pathogenesis of cholesteatomas to define the specific role of each cell type involved in this disease. Connective tissue mast cells have a complex retinue of functions mediated via the secretion of a variety of cytokines and proteinases, and many of the biologic phenomena in which mast cells are involved also are observed in cholesteatoma pathology. METHODS: The authors evaluated by immunohistochemistry 36 cholesteatomas of all types (e.g., primary and secondary acquired, recurrent, and congenital) and 23 specimens of normal tissues (e.g., tympanic membrane, canal wall skin, and postauricular skin) for the expression of tryptase, a mast cell-specific protease. RESULTS: Cholesteatomas showed approximately threefold to sevenfold increase in the concentration of mast cells when compared with that of normal tissues. In addition, 19-34% of the mast cells were found within the suprabasal layers of the squamous epithelium of cholesteatoma subgroups, a phenomenon observed only in grossly inflamed tympanic membrane specimens, but not in other control tissues including minimally inflamed tympanic membranes. CONCLUSIONS: The authors conclude from these data that mast cells may represent a previously unrecognized host inflammatory cell, which plays an important role in the development of one or more traits of cholesteatoma pathology.

Crystallization and preliminary crystallographic analysis of mannitol dehydrogenase (MtDH) from the common mushroom Agaricus bisporus.

Mannitol dehydrogenase (MtDH) is a key enzyme controlling the reductive synthesis of mannitol from fructose in the common mushroom Agaricus bisporus. A better understanding of the control of mannitol metabolism can be obtained by studying the structure of this enzyme. Here, the purification and crystallization of recombinant MtDH are reported. Crystals generally belonged to the space group C2, with unit-cell parameters a = 227, b = 125, c = 133 A, beta = 118 degrees, and diffracted to at least 1.8 A resolution, although a tantalum derivative belonged to the space group P2(1) and diffracted to the lower resolution of 2.9 A.

The crystallographic structure of the mannitol 2-dehydrogenase NADP+ binary complex from Agaricus bisporus.

Mannitol, an acyclic six-carbon polyol, is one of the most abundant sugar alcohols occurring in nature. In the button mushroom, Agaricus bisporus, it is synthesized from fructose by the enzyme mannitol 2-dehydrogenase (MtDH; EC ) using NADPH as a cofactor. Mannitol serves as the main storage carbon (up to 50% of the fruit body dry weight) and plays a critical role in growth, fruit body development, osmoregulation, and salt tolerance. Furthermore, mannitol dehydrogenases are being evaluated for commercial mannitol production as alternatives to the less efficient chemical reduction of fructose. Given the importance of mannitol metabolism and mannitol dehydrogenases, MtDH was cloned into the pET28 expression system and overexpressed in Escherichia coli. Kinetic and physicochemical properties of the recombinant enzyme are indistinguishable from the natural enzyme. The crystal structure of its binary complex with NADP was solved at 1.5-A resolution and refined to an R value of 19.3%. It shows MtDH to be a tetramer and a member of the short chain dehydrogenase/reductase family of enzymes. The catalytic residues forming the so-called catalytic triad can be assigned to Ser(149), Tyr(169), and Lys(173).

Expression of p53 protein in human middle ear cholesteatomas: pathogenetic implications.

BACKGROUND: Cholesteatoma is a destructive lesion of the middle ear or mastoid process or both. The molecular and cellular defects that result in the clinical hallmarks of acquired and congenital cholesteatomas, namely invasion, migration, uncoordinated proliferation, altered differentiation, aggressiveness, and recidivism, are unknown. Determining the existence of defects in the normal biology, biochemistry, and genetic complement of the major cellular constituents comprising a cholesteatoma (i.e., fibroblasts and keratinocytes) is critical to the understanding of the pathogenesis of cholesteatomas. It has been speculated that the development of human cholesteatomas is due, in part, to the altered control of cellular proliferation, which tilts the balance toward the aggressive, invasive growth of squamous epithelium within the middle ear. However, whether this altered control is due to defects in the mechanisms and underlying genes that control proliferation, or to cytokines released from infiltrating inflammatory cells, or to some other mechanism is unknown. The nuclear phosphoprotein p53 tumor suppressor gene plays a critical regulatory role in cell cycle control and apoptosis. In the current article, the authors have analyzed congenital, primary and secondary acquired, and recurrent cholesteatomas for the altered expression of p53 and Ki-67, a marker of active proliferation. METHODS: p53 and Ki-67 expression was determined by immunohistochemical assays using specific monoclonal antibodies. RESULTS: The authors' results indicate that p53 is elevated 9- to 20-fold in all cholesteatomas when compared to the expression of p53 in normal postauricular skin or tympanic membrane. However, there is no concomitant increase in Ki-67 expression in cholesteatomas. CONCLUSIONS: These data indicate a defect in cholesteatomas in the mechanisms that p53 engages (i.e., cell cycle control or apoptosis or both). In addition, these data further suggest that there is no intrinsic difference between any clinicopathologic group of cholesteatomas, at least with respect to p53-expression and, presumably, p53 function.

Mapping the antigenicity of copper-treated cellular prion protein with the scrapie isoform.

When recombinant and cellular prion protein (PrP(C)) binds copper, it acquires properties resembling the scrapie isoform (PrP(Sc)), namely protease resistance, detergent insolubility and increased beta sheet content. However, whether the conformations of PrP(C) induced by copper and PrP(Sc) are similar has not been studied in great detail. Here, we use a panel of seven monoclonal antibodies to decipher the epitopes on full-length mouse PrP(C) that are affected by exogenous copper, and to compare the antigenicity of the copper-treated full-length PrP(C) with the full-length PrP(Sc) present in scrapie-infected mouse brains. In the presence of copper, we found that epitopes along residues 115-130 and 153-165 become more accessible on PrP(C). These regions correspond to the two beta sheet strands in recombinant PrP and they were proposed to be important for prion conversion. However, when we compared the antibody-binding patterns between full-length PrP(C) with full-length PrP(Sc) and between copper-treated full-length PrP(C) with full-length PrP(Sc), antibody binding to residues 143-155 and 175-185 was consistently increased on PrP(Sc). Collectively, our results suggest that copper-treated full-length PrP(C) does not resemble full-length PrP(Sc), despite acquiring PrP(Sc)-like properties. In addition, since each full-length protein reacts distinctively to some of the antibodies, this binding pattern could discriminate between PrP(C) and PrP(Sc).

DNA analysis of human cholesteatomas.

HYPOTHESIS: The hypothesis tested in this article is that if cholesteatomas are a low-grade squamous cell neoplasm, then evidence of genetic instability, in the form of abnormal or aneuploid amounts of DNA, should be evident. BACKGROUND: Cholesteatoma is a destructive lesion of the middle ear and/or mastoid process that produces complications by erosion of the temporal bone. The clinical hallmarks of cholesteatomas, namely invasion, migration, uncoordinated proliferation, altered differentiation, aggressiveness, and recidivism, are traits typically associated with the neoplastic cell. However, there is little evidence to support or refute the speculation that cholesteatomas are a low-grade squamous cell neoplasm. the existence of defects in the genetic complement of the major cellular constituents comprising a cholesteatoma, fibroblasts and keratinocytes, would support the speculation that cholesteatomas are a neoplasm, since cancers commonly manifest quantitative and qualitative alterations in the normal euploid complement of genetic information, resulting in a cell that has an abnormal or aneuploid amount of DNA. METHODS: DNA content (ploidy) within cholesteatoma tissues was measured by flow cytometry and image analysis. RESULTS: The DNA content of 11 human cholesteatomas and nine postauricular skin specimens was analyzed using flow cytometry, while the DNA content of 10 cholesteatoma specimens was analyzed using image analysis. Interpretable data was obtained from 10 cholesteatoma specimens and six postauricular skin specimens. One cholesteatoma specimen demonstrated an abnormal aneuploid DNA content, whereas the remaining nine cholesteatomas and the six postauricular skin specimens demonstrated a normal euploid DNA content. CONCLUSIONS: We conclude that, due to the lack of overt genetic instability, as evidenced by the presence of a normal euploid DNA content, cholesteatomas are not low-grade neoplasms.