[Ketosis-prone atypical diabetes mellitus: report of two cases]

An atypical presentation of diabetes mellitus was described in black subjects, initially in adolescents by Winter et al. then, in adult populations. The principal characteristics of "African" diabetes are an acute onset with severe hyperglycemia and ketosis, and a clinical course of type 2 diabetes mellitus. In the subsequent clinical course after initiation of insulin therapy, prolonged remission is often possible with cessation of insulin therapy and maintenance of appropriate metabolic control. In the subsequent clinical course after initiation of insulin therapy, prolonged remission is often possible with cessation of insulin therapy and maintenance of appropriate metabolic control. The molecular mechanisms underlining the insulin secretory dysfunction are still to be understood and may involve glucolipotoxicity processes. The HLA alleles associated with susceptibility to type 1 diabetes were reported of high frequency in some populations with this form of diabetes, in the absence of makers of pancreatic beta cell autoimmunity. The aim of the present review is to discuss two cases of African diabetes and review the specific diagnostic, metabolic, pathogenic and management features of this atypical diabetes.

[Cushing's syndrome due to a pulmonary carcinoid]

Cushing paraneoplasic syndrome is a rare cause of hypercorticism. We report a case of 35 year-old man presenting with Cushing's syndrome characterized by severe signs of hypercorticism and hypokalemia. Endocrine investigations were suggestive of an hypercortisolism linked to an ectopic adrenocorticotropic (ACTH) secretion, both at baseline (mean ACTH levels=275 pg/ml, urinary free cortisol excretion=3.898 mmol/24 h) and after pharmacodynamic testing (lack of inhibition of ACTH by dexamethasone). Thoracic tomodensitometric examination revealed a 15 mm tumor corresponding to a neuroendocrine pulmonary carcinoid with positive immunostaining for chromogranin A. Postoperative ACTH measurement was undetectable, plasma cortisol and free urinary cortisol were also decreased after tumor resection suggesting complete tumor removal. This case report illustrates the characteristics of paraneoplasic Cushing syndrome due to ACTH secreting pulmonary neuroendocrine carcinoid.

Hypomethylation of DNA and resistance to apoptosis in tonsillar hypertrophy in children

We analyzed the hypomethylation of DNA and the sensitivity to apoptosis of tonsillar cells and peripheral blood lymphocytes (PBL) in twenty children with either recurrent tonsillitis (RT) or tonsillar hypertrophy (TH). We found no significant differences in DNA methylation of PBL obtained from RT and TH groups. Hypomethylation of DNA extracted from tonsillar tissue was higher in TH than in RT and was associated with lower spontaneous and thapsigargin-induced apoptosis. By contrast, RT showed a low level of DNA hypomethylation and was associated with high sensitivity to spontaneous and thapsigargin-induced apoptosis.

GCUNC-45 is a novel regulator for the progesterone receptor/hsp90 chaperoning pathway

The hsp90 chaperoning pathway is a multiprotein system that is required for the production or activation of many cell regulatory proteins, including the progesterone receptor (PR). We report here the identity of GCUNC-45 as a novel modulator of PR chaperoning by hsp90. GCUNC-45, previously implicated in the activities of myosins, can interact in vivo and in vitro with both PR-A and PR-B and with hsp90. Overexpression and knockdown experiments show GCUNC-45 to be a positive factor in promoting PR function in the cell. GCUNC-45 binds to the ATP-binding domain of hsp90 to prevent the activation of its ATPase activity by the cochaperone Aha1. This effect limits PR chaperoning by hsp90, but this can be reversed by FKBP52, a cochaperone that is thought to act later in the pathway. These findings reveal a new cochaperone binding site near the N terminus of hsp90, add insight on the role of FKBP52, and identify GCUNC-45 as a novel regulator of the PR signaling pathway.

[Tuberculous osteoarthritis of the foot in the diabetic: not unrecognize this diagnostic trap. About one case]

Osteoarticular tuberculosis is the fourth leading extrapulmonary localization of tuberculosis. The disease has a progressive course and is often diagnosed in the stage of bone destruction, causing an important diagnostic problem in diabetics with nervous osteoarthropathy. We report the case of a 23-year-old patient with multicomplicated diabetes type 1, treated for pulmonary tuberculosis who consulted after a trauma distended the left ankle. Bone biopsy was performed because of the diagnostic doubt between diabetes and infectious osteoarthropathy. Pathology reported active tuberculosis. Osteoarticular tuberculosis is still a severe disease because of the functional prognosis that requires early diagnosis, a difficult task in some conditions particularly in the diabetic where the disease may mimic nervous osteoarthropathy. Bone biopsy should be performed if there is a doubt.

[Incidence of factors favoring recurrent foot ulcers in diabetic patients]

BACKGROUND

Patients with foot ulcers have a high risk of relapse and amputation. Several studies have reported that 28 to 51% of amputated diabetics will have a second amputation of the lower limb within five years of the first amputation. The purpose of this study was to assess the incidence of factors favoring relapse within two years.

MATERIAL AND METHODS

One hundred ten diabetic patients were treated for foot lesions in the Casablanca Ibn Rochd university hospital between 1997 and 2000. Ninety of these patients attended review consultations.

RESULTS

There were 42 cases of relapse (46.6%). Male gender predominated in the relapse patients with a sex ratio of 3.2. Mean age at relapse was 55 years; 71.5% of the patients had type 2 diabetes. Lesions observed were neuropathic ulcer (n=23), arterial ulcer (n=6), infected wounds (n=13). Revealing factors were burns and wounds. The main risk factors were neuropathy (n=23, 52%), neuroarteriopathy (n=12, 31%), peur arteriopathy (n=6, 12%). Patients who relapsed (n=42) were significantly different from patients who did not relapse (n=48) for gender, presence or absence of neuropathy, and presence or absence of arteriopathy.

DISCUSSION

Secondary preventive measures against these risk factors, medical care, and specialized follow-up were satisfactory in these patients. our findings illustrate the importance of specialized management of diabetic patients with foot lesions. Adequate care of the lesions and preventive measures against risk factors are needed.

[Primary lymphoma of the thyroid gland]

Malignant primary lymphoma of the thyroid gland is a rare disease generally occurring women in the 6(th) or 7(th) decade of life. The principal clinical sign is giant goiter rapidly leading to sings of compression, raising the question of differential diagnosis with anaplastic cancer. The radiological findings in our patient were suggestive of malignancy due to the locoregional invasion. Immunohistochemistry study of the surgical specimen was required to reach the definitive diagnosis of thyroid gland primary lymphoma. Diagnosis of malignant primary lymphoma of the thyroid gland made at the stage of extensive locoregional extension compromises prognosis. Our patient died after one session of chemotherapy.

HSP40 binding is the first step in the HSP90 chaperoning pathway for the progesterone receptor

The progesterone receptor (PR) can be isolated in its native conformation able to bind hormone, yet its ligand-binding domain rapidly loses its activity at elevated temperature. However, an in vitro chaperoning system consisting of five proteins (HSP40, HSP70, HOP, HSP90, and p23) with ATP is capable of restoring this function. The first step of this chaperoning mechanism is usually thought to be the binding of HSP70 to PR. Our findings here show that the binding of HSP40 to PR is, instead, the first step. HSP40 binding occurred rapidly and was not dependent on ATP or other proteins. The stoichiometry of HSP40 to native PR in these complexes was approximately 1:1. HSP40 bound specifically and with a high affinity to native PR (K(d) = 77 nm). The binding of HSP40 to PR was sustained and did not interact in the highly dynamic fashion that has been observed previously for HSP90 in this system. The HSP40 small middle dotPR complex could be isolated as a functional unit that could, after the addition of the other chaperones, progress to a PR complex capable of hormone binding. These results indicate that HSP40 initiates the entry of PR into the HSP90 pathway.

The N-terminal adenosine triphosphate binding domain of Hsp90 is necessary and sufficient for interaction with estrogen receptor

To understand how the molecular chaperone Hsp90 participates in conformational maturation of the estrogen receptor (ER), we analyzed the interaction of immobilized purified avian Hsp90 with mammalian cytosolic ER. Hsp90 was either immunoadsorbed to BF4 antibody-Sepharose or GST-Hsp90 fusion protein (GST.90) was adsorbed to glutathione-Sepharose. GST.90 was able to retain specifically ER, similarly to immunoadsorbed Hsp90. When cells were treated with estradiol and the hormone treatment was maintained during cell homogenization, binding, and washing steps, GST.90 still interacted efficiently with ER, suggesting that ER may form complexes with Hsp90 even after its activation by hormone and salt extraction from nuclei. The GST.90-ER interaction was consistently reduced in the presence of increasing concentrations of potassium chloride or when cytosolic ER-Hsp90 complexes were previously stabilized by molybdate, indicating that GST.90-ER complexes behave like cytosolic Hsp90-ER complexes. A purified thioredoxin-ER fusion protein was also able to form complexes with GST.90, suggesting that the presence of other chaperones is not required. ER was retained only by GST.90 deletion mutants bearing an intact Hsp90 N-terminal region (1-224), the interaction being more efficient when the charged region A was present in the mutant (1-334). The N-terminal fragment 1-334, devoid of the dimeric GST moiety, was also able to interact with ER, pointing to the monomeric N-terminal adenosine triphosphate binding region of Hsp90 (1-224) as the region necessary and sufficient for interaction. These results contribute to understand the Hsp90-dependent process responsible for conformational competence of ER.

[Screening for diabetic retinopathy with ophthalmoscopy: the contribution of non-ophthalmologist practitioners seems possible]

Diabetic retinopathy is a severe and frequent complication of diabetes. Screening and early treatment of retinal lesions avoid blindness, but diagnosis is often established too late. The purpose of our study was to compare the concordance between the results of examination of fundus oculi whether performed by a previously trained non ophthalmologist physician at diabetes day center or during a routine ophthalmology consultation. Results were classified a posteriori in order to have binary response (presence of the lesion, absence of the lesion). Ninety six eyes were examined. Results of these examinations were compared using the kappa test agreement (kappa). The concordance was good for the majority of retinal lesions. The concordance in the results suggests that the contribution of non ophthalmologist physicians to the screening of diabetic retinopathy is possible and could facilitate the selection of patients who require specialized and elaborate ophthalmologic exploration.

The heat shock protein 90 antagonist novobiocin interacts with a previously unrecognized ATP-binding domain in the carboxyl terminus of the chaperone

Heat shock protein 90 (Hsp90), one of the most abundant chaperones in eukaryotes, participates in folding and stabilization of signal-transducing molecules including steroid hormone receptors and protein kinases. The amino terminus of Hsp90 contains a non-conventional nucleotide-binding site, related to the ATP-binding motif of bacterial DNA gyrase. The anti-tumor agents geldanamycin and radicicol bind specifically at this site and induce destabilization of Hsp90-dependent client proteins. We recently demonstrated that the gyrase inhibitor novobiocin also interacts with Hsp90, altering the affinity of the chaperone for geldanamycin and radicicol and causing in vitro and in vivo depletion of key regulatory Hsp90-dependent kinases including v-Src, Raf-1, and p185(ErbB2). In the present study we used deletion/mutation analysis to identify the site of interaction of novobiocin with Hsp90, and we demonstrate that the novobiocin-binding site resides in the carboxyl terminus of the chaperone. Surprisingly, this motif also recognizes ATP, and ATP and novobiocin efficiently compete with each other for binding to this region of Hsp90. Novobiocin interferes with association of the co-chaperones Hsc70 and p23 with Hsp90. These results identify a second site on Hsp90 where the binding of small molecule inhibitors can significantly impact the function of this chaperone, and they support the hypothesis that both amino- and carboxyl-terminal domains of Hsp90 interact to modulate chaperone activity.

Dimerization and N-terminal domain proximity underlie the function of the molecular chaperone heat shock protein 90

Heat shock protein (hsp)90 functions in a complex chaperoning pathway where its activity is modulated by ATP and by interaction with several co-chaperones. One co-chaperone, p23, binds selectively to the ATP-bound state of hsp90. However, the isolated ATP-binding domain of hsp90 does not bind p23. In an effort to identify the p23-binding domain, we have constructed a series of hsp90 deletion mutants fused with glutathione-S-transferase (GST). Full-length GST-hsp90 is able to bind p23, and also, to chaperone assembly of progesterone receptor complexes. Truncations from the C terminus of GST-hsp90 reveal a C-terminal boundary for the p23-binding domain at approximately residue 490. This fragment contains, in order, the ATP-binding domain, a highly charged region, and 203 residues beyond the charged region. p23 binding is unaffected by deletion of the charged region, indicating that two noncontiguous regions of hsp90 are involved in p23 binding. These regions are only effective when hsp90 is in a dimeric state as shown by loss of p23 binding upon removal of GST or as shown by use of FK506-binding protein12-hsp90 constructs that form dimers and bind p23 only in the presence of a bivalent drug. Thus, p23 binding requires an hsp90 dimer with close proximity between N-terminal regions of hsp90 and a conformation specified by ATP.

Hsp90 chaperone activity requires the full-length protein and interaction among its multiple domains

Hsp90 is an abundant and ubiquitous protein involved in a diverse array of cellular processes. Mechanistically we understand little of the apparently complex interactions of this molecular chaperone. Recently, progress has been made in assigning some of the known functions of hsp90, such as nucleotide binding and peptide binding, to particular domains within the protein. We used fragments of hsp90 and chimeric proteins containing functional domains from hsp90 or its mitochondrial homolog, TRAP1, to study the requirements for this protein in the folding of firefly luciferase as well as in the prevention of citrate synthase aggregation. In agreement with others who have found peptide binding and limited chaperone ability in fragments of hsp90, we see that multiple fragments from hsp90 can prevent the aggregation of thermally denatured citrate synthase, a measure of passive chaperoning activity. However, in contrast to these results, the luciferase folding assay was found to be much more demanding. Here, folding is mediated by hsp70 and hsp40, requires ATP, and thus is a measure of active chaperoning. Hsp90 and the co-chaperone, Hop, enhance this process. This hsp90 activity was only observed using full-length hsp90 indicating that the cooperation of multiple functional domains is essential for active, chaperone-mediated folding.

The molecular chaperone Hsp90 can negatively regulate the activity of a glucocorticosteroid-dependent promoter

Hsp90, a molecular chaperone required for the functioning of glucocorticosteroid receptor (GR), ensures, by direct interaction, the conformational competence of the steroid-binding pocket. In addition to having this positive function, Hsp90 maintains steroid receptors in an inactive form in the absence of hormone. However, neither the participation of Hsp90 once the pathway has been activated by the ligand nor the importance of increased Hsp90 levels in determining the amplitude of the response has ever been assessed directly. Here, by increasing the Hsp90/GR ratio in the nuclear compartment, we found an attenuation of the response to glucocorticosteroids that was not due to a nonspecific or toxic effect of the Hsp90 modified by nuclear targeting. Since this negative effect was more pronounced at high levels of hormone, when receptor and Hsp90 are maximally dissociated, the possibility of an interaction between Hsp90 and GR, already activated to a DNA-binding form, was directly investigated. Indeed GR, after in vivo activation by ligand, was still able to reassociate with Hsp90, suggesting that this interaction plays a role in vivo, possibly in receptor recycling. Moreover, the GR binding to its DNA response element was inhibited by an excess of Hsp90, pointing to a function of Hsp90 in the nuclear compartment. It is thus proposed that an increased Hsp90/GR ratio influences the responsiveness to ligand at a step that is after receptor activation. This increased ratio may be of pathophysiological relevance in the different circumstances that lead to an elevated level of nuclear Hsp90.

Heat-induced oligomerization of the molecular chaperone Hsp90. Inhibition by ATP and geldanamycin and activation by transition metal oxyanions

It has been previously reported that heat shock protein 90 (Hsp90) oligomerizes at high temperatures and displays concomitantly a novel chaperone activity (Yonehara, M., Minami, Y., Kawata, Y., Nagai, J., and Yahara, I. (1996) J. Biol. Chem., 271, 2641-2645). In order to better define these oligomerization properties at high temperatures and to know whether they are influenced by modulators of Hsp90 function, heat-induced oligomerization of highly purified dimeric Hsp90 has been investigated over a wide range of temperature and protein concentrations by native polyacrylamide gel electrophoresis and size exclusion chromatography. Whereas below 50 degreesC, the dimeric form is maintained over a large range of concentrations, at the critical temperature of 50 degreesC, a sharp transition from dimeric to higher order oligomeric species takes place within minutes, in a highly ordered process, suggesting that a conformational change, leading to the appearance of a new oligomerization site, occurs in Hsp90 dimer. Moreover, at and above the critical temperature, the extent of oligomerization increases with Hsp90 concentration. Formation of high order oligomers at high temperatures is sensitive to modulators of Hsp90 function. ATP and geldanamycin, both known to bind to the same pocket of Hsp90, are inhibitors of this process, whereas molybdate, vanadate, and Nonidet P-40, which are thought to increase surface hydrophobicity of the protein, are activators. Thus, oligomerization of Hsp90 at high temperatures may be mediated through hydrophobic interactions that are hindered by ligands and favored by transition metal oxyanions. The fact that the heat-induced oligomerization of Hsp90 is affected by specific ligands that modulate its properties also suggests that this process may be involved in cell protection during heat shock.

Presence of an aromatase inhibitor, possibly heat shock protein 90, in dominant follicles of cattle

In cattle, it has been suggested that follicular fluid has direct modulatory effects on follicular growth and maturation. In the first part of this study, an in vitro test using aromatase activity of follicular wall fragments as an end point was validated for cattle follicles and was used to test whether follicular fluid (from dominant or non-dominant follicles) modulates aromatase activity. Fluid from dominant follicles at a concentration of 24 or 12% (obtained during the luteal and follicular phases, respectively) significantly inhibited aromatase activity. Inhibitory activity was low or absent in fluid from non-dominant follicles. FSH-stimulated aromatase activity was also reduced by fluid from dominant follicles, but not to a greater extent than in basal conditions. Finally, charcoal-treated fluid from dominant follicles retained its inhibitory activity. In contrast, ovarian venous serum draining a dominant follicle had no activity at the three concentrations tested (6, 12 and 24%). In the second part of the study, identification of the compounds involved in this modulatory activity was attempted using SDS-PAGE. Comparison of the fluorographs from de novo synthesized proteins stored in follicular fluid (inhibitory medium) with those secreted in incubation medium (inactive medium) demonstrated that one protein (90 kDa, pI 5.8) was significantly (P < 0.05) more abundant in fluid from dominant follicles (2.0 +/- 0.09%) than in the culture medium (1.3 +/- 0.1% of the total proteins). This protein had characteristics similar to those of heat shock protein 90 (hsp 90). Therefore, in the final part of the study, the presence of hsp 90 in ovarian cells and follicular fluid was investigated using immunohistochemistry and western blot analysis. After immunohistochemistry, a positive signal was detected mainly in the granulosa cells of larger follicles and to a smaller extent in thecal cells and oocytes. Western blot analysis also demonstrated the presence of hsp 90 in follicular wall fragments and fluid. When blotting was achieved on a sample of follicular fluid resolved by two-dimensional PAGE, the spot detected had a similar location to that at 90 kDa and pI 5.8. Addition of purified hsp 90 to bovine follicles in vitro depressed aromatase activity by altering the K(m) value (and possibly the Vmax value) of the enzyme. It is proposed that hsp 90 is a functional regulator of follicular maturation through its action on aromatase.

Production and characterization of a monoclonal antibody able to discriminate galectin-1 from galectin-2 and galectin-3

Antisera raised against galectin-1 exhibit crossreactivities with other galectins or related molecules. In order to overcome this problem, a monoclonal antibody to human brain galectin-1 was obtained by selecting clones without reactivity toward galectin-3. This mAb specifically bound galectin-1 of various animal origins but neither galectin-2 nor galectin-3. Western-blotting analysis of soluble human brain extracts after 2D gel electrophoresis revealed only the two most acidic isoforms of galectin-1. The ability of this mAb to bind galectin-1/asialofetuin complexes indicates that its epitope is not localized in the carbohydrate recognition domain of galectin-1. This particularity induces with efficiency its monospecificity.

Purification and characterization of a human brain galectin-1 ligand

Our previous studies have characterized an endogenous lectin from human brain identified as galectin-1. A soluble ligand of galectin-1 was purified from human brain by affinity chromatography and preparative electrophoresis. The purified ligand (termed HBGp82, for human brain galectin-1-binding polypeptide of 82,000 daltons) has an apparent molecular mass of 82 kDa and is glycosylated by N-linked biantennary complex structures. HBGp82 was partially characterized by microsequencing of peptide fragments. Similar peptides were found in a heat shock of protein of 90,000 daltons, hsp90. However, comparison of apparent molecular weights and matrix-assisted laser desorption mass spectrometry clearly showed that HBGp82 differs to some degree from hsp90.

Oligoclonal beta-galactoside-binding immunoglobulins antigenically related to 14 kDa lectin in human serum and cerebrospinal fluid: purification and characterization

1. An antiserum raised against a 14 kDa beta-galactoside specific lectin from human brain (HBL14) was used to probe blots from samples of serum and cerebrospinal fluid. The only HBL14-immunoreactive material detected was heavy and light chains of a beta-galactoside-binding IgG fraction (lectin-like IgG). 2. Lectin-like IgG, as well as IgG Fab fragments, compete with HBL14 for binding either to anti-HBL14 antibody or to a lactosyl polyacrylamide-based copolymer. 3. Purification of lectin-like IgG was obtained by affinity chromatography on immobilized rabbit anti-lectin immunoglobulins. The carbohydrate-binding specificity of the purified molecules was restricted to beta-Gal-containing structures and close to the HBL14 one.

Study of lectin-ganglioside interactions by high-performance liquid affinity chromatography

A high-performance affinity column containing immobilized modified GM1 (lyso-GM1) was used to study the binding of an endogenous human brain lectin (HBL) in comparison with other carbohydrate-binding proteins. The proteins are previously converted into biotinylated derivatives. Detection of biotinylated proteins in the eluates by a microtitre plate assay ensures good sensitivity. The maximum binding capacity of the adsorbent for HBL is obtained in Tris buffer supplemented with beta-mercaptoethanol. The binding is inhibitable by specific sugar. It is concluded that the use of immobilized glycolipids in analytical high-performance liquid affinity chromatographic methods may serve as models in the study of interactions between gangliosides and carbohydrate-binding proteins.

Development of screening methods for detection of carbohydrate-binding proteins by use of soluble glycosylated polyacrylamide-based copolymers

Mammalian endogenous carbohydrate-binding proteins (lectins) play fundamental roles in a variety of mechanisms of interactions both at the molecular and cellular levels. We have investigated the binding of one of them (human brain lectin) to soluble acrylamide copolymerized with derivatives of either lactose (O-beta-lactosyloxyallylallylaminoacrylamide copolymer) or D-mannose (D-alpha-mannosyloxyallylallylaminoacrylamide copolymer) in direct enzyme affinoassays, in an attempt to develop simple procedures for detection and estimation of its carbohydrate-binding activity. Biotinylated plant lectins were utilized as reference standards. Affinoassays employed the polymer dotted on nitrocellulose and the polymer coated on microtiter plates as well as detection of bound biotinylated lectin by streptavidin/horseradish peroxidase reagent. Both assays provided reproducible binding, inhibitable by specific sugars. The microtiter plate assay is well suited to sensitive detection of the negative endogenous lectin by competition with biotinylated brain lectin. We conclude that the use of derivatized acrylamide in dotting and microtiter plate assays may prove practical for detection of endogenous lectins and that such polymers may serve as model substances in the study of biological partners of these carbohydrate-binding proteins.

[Malignant lymphoma on a gastric stump]

We report a case of lymphoplasmocytic and immunoblastic gastric remnant lymphoma occurring in a 51 year-old male. This patient had undergone subtotal gastrectomy for a gastric peptic ulcer at age 37. Histologic findings in the initial gastric specimen showed a dense lymphoid infiltrate surrounding the ulcer within the gastric mucosa. This proliferation was grouped into distinct follicles, and was compatible with pseudo-lymphoma. The progression of pseudo-lymphoma to malignant lymphoma is suggested.