Clustering of Shaker-type K+ channels by interaction with a family of membrane-associated guanylate kinases

ANCHORING of ion channels at specific subcellular sites is critical for neuronal signalling, but the mechanisms underlying channel localization and clustering are largely unknown (reviewed in ref. 1). Voltage-gated K+ channels are concentrated in various neuronal domains, including presynaptic terminals, nodes of Ranvier and dendrites, where they regulate local membrane excitability. Here we present functional and biochemical evidence that cell-surface clustering of Shaker-subfamily K+ channels is mediated by the PSD-95 family of membrane-associated putative guanylate kinases, as a result of direct binding of the carboxy-terminal cytoplasmic tails to the K+ channel subunits to two PDZ (also known as GLGF or DHR) domains in the PSD-95 protein. The ability of PDZ domains to function as independent modules for protein-protein interaction, and their presence in other junction-associated molecules (such as ZO-1 (ref. 3) and syntrophin), suggest that PDZ-domain-containing polypeptides may be widely involved in the organization of proteins at sites of membrane specialization.

Heteromultimerization and NMDA receptor-clustering activity of Chapsyn-110, a member of the PSD-95 family of proteins

Chapsyn-110, a novel membrane-associated putative guanylate kinase (MAGUK) that binds directly to N-methyl-D-aspartate (NMDA) receptor and Shaker K+ channel subunits, is 70%-80% identical to, and shares an identical domain organization with, PSD-95/SAP90 and SAP97. In rat brain, chapsyn-110 protein shows a somatodendritic expression pattern that overlaps partly with PSD-95 but that contrasts with the axonal distribution of SAP97. Chapsyn-110 associates tightly with the postsynaptic density in brain, and mediates the clustering of both NMDA receptors and K+ channels in heterologous cells. Indeed, chapsyn-110 and PSD-95 can heteromultimerize with each other and are recruited into the same NMDA receptor and K+ channel clusters. Thus, chapsyn-110 and PSD-95 may interact at postsynaptic sites to form a multimeric scaffold for the clustering of receptors, ion channels, and associated signalling proteins.

GKAP, a novel synaptic protein that interacts with the guanylate kinase-like domain of the PSD-95/SAP90 family of channel clustering molecules

The molecular mechanisms underlying the organization of ion channels and signaling molecules at the synaptic junction are largely unknown. Recently, members of the PSD-95/SAP90 family of synaptic MAGUK (membrane-associated guanylate kinase) proteins have been shown to interact, via their NH2-terminal PDZ domains, with certain ion channels (NMDA receptors and K+ channels), thereby promoting the clustering of these proteins. Although the function of the NH2-terminal PDZ domains is relatively well characterized, the function of the Src homology 3 (SH3) domain and the guanylate kinase-like (GK) domain in the COOH-terminal half of PSD-95 has remained obscure. We now report the isolation of a novel synaptic protein, termed GKAP for guanylate kinase-associated protein, that binds directly to the GK domain of the four known members of the mammalian PSD-95 family. GKAP shows a unique domain structure and appears to be a major constituent of the postsynaptic density. GKAP colocalizes and coimmunoprecipitates with PSD-95 in vivo, and coclusters with PSD-95 and K+ channels/NMDA receptors in heterologous cells. Given their apparent lack of guanylate kinase enzymatic activity, the fact that the GK domain can act as a site for protein-protein interaction has implications for the function of diverse GK-containing proteins (such as p55, ZO-1, and LIN-2/CASK).

Failure of early postnatal dexamethasone to prevent chronic lung disease in infants with respiratory distress syndrome

OBJECTIVE

To study the effect of early postnatal dexamethasone (days 1-3) on the incidence and severity of chronic lung disease in preterm infants with respiratory distress syndrome.

METHODS

A multicentre, randomised, placebo controlled, blinded study was carried out in 18 neonatal intensive care units in Israel. The primary outcome measure was survival to discharge without requirement for supplemental oxygen therapy beyond 28 days of life. The secondary outcome measures were requirement for mechanical ventilation at 3 and 7 days, duration of ventilation or oxygen therapy, need for subsequent steroids for established chronic lung disease and incidence of major morbidities.

RESULTS

The study consisted of 248 infants (dexamethasone n = 132; placebo n = 116). No differences were found in the outcome variables except for a reduction in requirement for mechanical ventilation at age 3 days in treated infants (dexamethasone 44%, placebo 67%; P = 0.001). Gastrointestinal haemorrhage, hypertension, and hyperglycaemia were more common in treated infants, but no life threatening complications, such as gastrointestinal perforation, were encountered.

CONCLUSIONS

These data do no support the routine use of early postnatal steroids, but may justify further study in a selected, high risk group of infants.

Clinical predictors of acute response with quetiapine in psychotic mood disorders

BACKGROUND

In controlled studies of patients with schizophrenia, the atypical antipsychotic quetiapine, 300 mg/day, has been shown to be as effective in the treatment of positive and negative symptoms as haloperidol. However, little is known about the efficacy of quetiapine in patients with psychotic mood disorders. The purpose of this study was to assess the efficacy of quetiapine in the treatment of psychotic mood disorders in comparison with nonaffective psychotic disorders and identify clinical factors associated with quetiapine response.

METHOD

In a naturalistic setting, by reviewing medical records, we assessed response to quetiapine and factors associated with response to quetiapine in 145 consecutive patients newly treated with the drug at a nonprofit academic psychiatric hospital. These patients had received a discharge diagnosis of bipolar disorder (manic, mixed, or depressive type), major depression with psychotic features, schizophrenia, schizoaffective disorder (bipolar or depressive type), delusional disorder, or psychosis not otherwise specified (NOS) according to DSM-IV criteria.

RESULTS

Patients with a diagnosis of bipolar disorder, manic, mixed, or depressed and schizoaffective disorder, bipolar type displayed higher response rates (> 74%) compared with patients with schizophrenia. However, this finding did not achieve statistical significance. A diagnosis of major depression with psychotic features (p = .02) and longer duration of illness (p = .03) were associated with less chance of responding.

CONCLUSION

Quetiapine may be a useful alternative or adjunctive treatment for patients with bipolar and schizoaffective disorders.

The nifedipine gastrointestinal therapeutic system in the treatment of hypertension

As the number of antihypertensive agents increases, the choice of optimal therapy becomes more difficult. Certainly, hemodynamic derangements caused by the disease state as well as therapy must be considered. Patient convenience and quality of life are also issues that must be addressed. Preliminary experience suggests that the gastrointestinal therapeutic system (GITS) push-pull osmotic pump formulation of nifedipine is safe and efficacious in the treatment of hypertension. In 1 study, nifedipine GITS was compared with sustained-release propranolol in patients with mild to moderate hypertension already receiving diuretics. Using a 2-week placebo run-in, double-blind study design, patients were randomly assigned to receive nifedipine GITS (n = 31) in doses of 30, 60 or 90 mg once daily, or sustained-release propranolol (n = 32) in doses of 80, 160 or 240 mg once daily. Previous diuretic therapy was continued. Sitting and 5-minute standing blood pressure and heart rate measurements were obtained 24 hours after dosing. At the end point of treatment, both nifedipine GITS and sustained-release propranolol reduced blood pressure compared with placebo (p less than 0.001) in the sitting and standing positions. Nifedipine GITS was more effective than sustained-release propranolol in reducing standing (p less than 0.005) and sitting (p less than 0.001) systolic blood pressure and sitting diastolic blood pressure (p less than 0.02). Sustained-release propranolol caused a greater reduction in standing (p less than 0.001) and sitting (p less than 0.0006) resting heart rate than nifedipine GITS. Both drugs were well tolerated.(ABSTRACT TRUNCATED AT 250 WORDS)

Multicenter comparison of the nifedipine gastrointestinal therapeutic system and long-acting propranolol in patients with mild to moderate systemic hypertension receiving diuretics. A preliminary experience

The efficacy and safety of nifedipine in a gastrointestinal therapeutic system (GITS) push-pull osmotic pump formulation was compared with long-acting propranolol in 49 patients with mild to moderate hypertension already receiving diuretics. Using a two-week placebo run-in, double-blind study design, patients were randomly assigned to receive nifedipine GITS (n = 24) in doses of 30 mg, 60 mg, or 90 mg once daily; or long-acting propranolol (n = 25) in doses of 80, 160, or 240 mg once daily. Previous diuretic therapy was continued. Sitting and five-minute standing blood pressure and heart rate measurements were made 24 hours after dosing. At the endpoint of treatment, both nifedipine GITS and sustained-release propranolol reduced blood pressure compared with placebo (p less than 0.001) in the sitting and standing positions. Nifedipine GITS was more effective in lowering standing systolic blood pressure than was propranolol (p less than 0.02). Propranolol caused a greater reduction in resting heart rate than did nifedipine GITS (p less than 0.003). Both drugs were well tolerated. Nifedipine GITS is an effective and safe once-daily drug for use in patients with hypertension who are already receiving diuretics, may be more effective than sustained-release propranolol, and may be better tolerated than conventional nifedipine capsules.

Experimental evidence of surface-plasmon coupling in anisotropic hollow nanoparticles

We report on the investigation of surface-plasmon excitation of anisotropic WS(2) hollow nanoparticles in a near-field geometry by means of a scanning transmission electron microscope. The shell thickness influence on the electron-energy-loss-spectroscopy spectra is experimentally observed and is analyzed within a classical dielectric formalism. As for the isotropic case, we evidence one symmetric (tangential) and one antisymmetric (radial) mode. We point out the intriguing fact that, for the anisotropic case, one can relate these modes to the interband transition of the in-plane component of the dielectric tensor and to the bulk-plasmon energy of the out-of-plane component.

[Causes of death of children at the Hôpital des Enfants-Malades. Statistical study of 1 098 pathologic and clinical records collected from 1966 to 1975 (author's transl)]

The clinical and histopathologic records of 1 098 children under 15 years of age, deceased at the hôpital des Enfants-Malades from 1966 to 1975 were studied. This material represents 44% of the total deaths of the same period. This study uses both the international classification of diseases and W.H.O.'s criteria, for distinguishing in causes of death between the principal cause, the immediate cause and associated causes. A higher mortality rate was observed in boys (58%), during the first year of life (80%), during the first 12 hours following admission (13%) and during the night. Causes of death are rarely isolated (10%), more often multiple: double (50%), or even triple or more (40%). Malformations represent 40% of the main causes of death, infections 14%, perinatal mortality 11%. Among immediate causes, infectious diseases are responsible for 23% of the deaths, respiratory disorders for 15%. Among associated causes are seen, in decreasing order of frequency: surgical procedures, prematurity, known or unrecognized associated malformations. Infections occurring during hospitalization represent the principal iatrogenic disorders. Anatomico-clinical examination failed to find an immediate cause of death in 25% of the cases and a principal cause in 7%.

Inhibition of UDP-glucose: protein transglucosylase by a maize endosperm protein factor

UDP-glucose: protein transglucosylase (UPTG, EC 2.4.1.112) catalyzes the first step of protein-bound alpha-glucan synthesis in potato tuber and developing maize endosperm. The presence of a non-dialyzable, heat labile protein responsible for low levels of UPTG activity in developing maize endosperm was investigated. UPTG activity in 5-day old maize seedlings and potato tuber solubilized preparations was also reduced by the endosperm preparation. FPLC-Mono Q column chromatography of developing maize endosperm was effective in separating the inhibitor protein (IP) from UPTG. After gel filtration on Superose 12, IP yielded a major polypeptide of about 80 kDa on SDS-PAGE. IP was purified by gel filtration on Superose 12 and preparative SDS-PAGE, and specific antibodies were prepared. Polyclonal antibodies reacted specifically with an 80 kDa polypeptide of developing maize endosperm on Western blot. They also recognized a similar band in 5-day old maize seedlings, but not in potato tubers. The identification of a factor that regulates the level of UPTG activity in developing maize endosperm may help to elucidate the functional role of the enzyme in the initiation of starch synthesis during seed development.

Identification of a UPTG inhibitor protein from maize endosperm: high homology with sucrose synthase protein

A thermolabile UPTG inhibitor protein (IP) was isolated and purified from a developing maize endosperm preparation. High homology of two internal peptides of IP with known plant sucrose synthase (SS) sequences suggested that IP might be related somehow with SS. IP and SS activities were found in the same preparation and showed thermolability between 60-65 degrees C. IP and SS activities presented the same ionic charge and molecular mass in native conditions (Mono Q and Superose-12 columns chromatographies). Western blot experiments with an anti-SS antibody as well as with an anti-IP antibody showed a single 80 kDa polypeptide band where IP and SS activities were present. Anti-SS antibody can neutralize SS as well as IP activities in a neutralization assay. It was found that in the maize mutant shrunken-1, lacking SS1 protein, the UPTG activity was not inhibited. Furthermore, the solubilized preparation of the sh1 endosperm is unable of inhibiting UPTG activity from potato tuber. The high correlation between IP and SS properties suggests that IP might be in fact a form of SS. Moreover, the relation between IP and the SS1 isoform is discussed. So, a new biological activity of SS is suggested.