核蛋白基本单元的合成－O－乙基－UMP－丙氨酸甲酯

在合成磷酰蛋白的模型化合物体Ｎ－（Ｏ,Ｏ－二烷基）磷酰化氨基酸（１）的基础上,首次合成了有机磷生命化学的模型化合物──核蛋白基本单元Ｎ－（Ｏ－烷基,Ｏ－核苷）磷酰化氨基酸（２）,并对上述物质进行了分离、鉴定、比较了两种模型的合成方法。这对在小分子水平上,深入研究磷酰基的参与作用和蛋白质与核酸之间的互相作用机理提供了较好的模型化合物。     

Mother-infant bonding

A study of the research on postpartum mother-infant bonding shows that results from poorly constructed research programs were published in major journals and became a part of hospital policy because the bonding concept was politically useful in the struggle between advocates of natural childbirth and managers of the medical model of birth. The concept was also uncritically accepted because it was consistent with a longstanding ideology of motherhood that sees women as the prime architects of their children’s personalities. Diane Eyer earned her Ph.D. in developmental psychology from the University of Pennsylvania. She is currently writing a book on the ways in which the concepts of bonding and attachment have affected our understanding of appropriate early childcare.     

Choline derivatives and sodium fluoride protect acetylcholinesterase against irreversible inhibition and aging by DFP and paraoxon

A light addressable potentiometric sensor was used to measure acetylcholinesterase (AChE) activity in order to evaluate the protective effects of quaternary compounds and NaF against enzyme phosphorylation and aging by two organophosphates. The use of the immobilized AChE made possible the quick removal of reagents (i.e., organophosphate, 2-pralidoxime, and protectant), thereby permitting accurate determination of AChE activity before and after phosphorylation and aging. Paraoxon was 15-fold more potent in inhibiting AChE than DFP, while the percent aging following phosphorylation by diiso-propylfluorophosphate (DFP) was much higher. Sodium fluoride (NaF), the most effective protectant against phosphorylation and aging, and the quaternary ammonium compounds reduced significantly AChE inhibition by DFP and paraoxon, to similar degrees. Even though the percent AChE activity that was lost to aging was reduced by these agents, aging as a percent of phosphorylated AChE was not reduced. Thus, their major effect was in reducing the percent AChE phosphorylation, which consequently resulted in reduction of total aged AChE. The finding that quaternary ammonium compounds protect against phosphorylation is consonant with the proposed presence of the active site of AChE in an aromatic gorge.     

Membrane-delimited cell signaling complexes: Direct ion channel regulation by G Proteins

Summary Ion channels are signaling molecules and by them-selves perform no work. In this regard they are un like the usual membrane enzyme effectors for G proteins. The pathways of G protein receptor, G protein and ion channels are, therefore, purely infor mational in function. Because a single G protein may have several ion channels as effectors, the effects should be coordinated and this seems to be the case. Inhibition of Ca²⁺ current and stimulation of K⁺ currents would have a greater impact than either alone. Additional flexibility is provided by spontane ous noise in the complexes of G protein receptor, G protein, and ion channel. By having a non-zero setpoint, the range of control is extended and the responses become bi-directional.     

Binding of sulfosuccinimidyl fatty acids to adipocyte membrane proteins: Isolation and ammo-terminal sequence of an 88-kD protein implicated in transport of long-chain fatty acids

Summary We recently reported (Harmon et al., J. Membrane Biol. 124:261–268, 1991) that sulfo-N-succinimidyl derivatives of long-chain fatty acids (SS-FA) specifically inhibited transport of oleate by rat adipocytes. These compounds bound to an 85–90 kD membrane protein which was also labeled by another inhibitor of FA transport [³H]DIDS (4,4-diisothiocyanostilbene-2-2-sulfonate). These results indicated that the protein was a strong candidate as the transporter for long-chain fatty acids. In this report we determined that the apparent size of the protein is 88 kD and its isoelectric point is 6.9. We used [³H]SS-oleate (SSO), which specifically labels the 88-kD protein, to isolate it from rat adipocyte plasma membranes. Identification of 15 amino acids at the N-terminus region revealed strong sequence homology with two previously described membrane glycoproteins: CD36, a ubiquitous protein originally identified in platelets and PAS IV, a protein that is enriched in the apical membranes of lipidsecreting mammary cells during lactation. Antibody against PAS IV cross-reacted with the adipocyte protein. This, together with the N-terminal sequence homology, suggested that the adipocyte protein belongs to a family of related intrinsic membrane proteins which include CD36 and PAS IV.     

Whole-cell recording of neuroblastoma x glioma cells during downregulation of a major substrate, 80K/MARCKS,of protein kinase C

Summary Differentiated neuroblastoma cells exhibit both the delayed rectifier potassium current (I _K) and the M-current (I _M). The present study was designed to determine the roles of protein kinase C (PKC) and of the calmodulin-binding protein 80K/MARCKS, a prominent substrate for PKC and possible regulator of these currents. Neuroblastoma x glioma (NG108-15) hybrid cells transfected with m1 muscarinic receptors were grown with 1% fetal bovine serum (FBS) without the prostaglandin E₁ (PGE₁) and isobutylmethylxanthine (IBMX) usually added in preparation for electrophysiological studies. Under these conditions, the usual pleomorphism was largely abolished, leaving two populations of small cells with stellate and spherically symmetrical geometries. Whole-cell patch clamping indicated that the two cell types had identical electrophysiological properties, displaying: I _k, a small current through a T-like Ca²⁺ channel, and no M-current.Stimulation with carbachol shifted the distribution of cells to a more stellate morphology within 24 hr and later (after 48 hr) reduced the PKC substrate 80K/MARCKS by 22±7%. In contrast to the stimulation of I _k observed with cardiac cells, PKC activation produced only a small inhibition of I _k, which was independent of carbachol pretreatment. Thus, PKC and 80K/MARCKS can be dissociated from the regulation of I _k in neuroblastoma cells.Supported in part by research grants from the National Institutes of Health (DK-40145 and EY-08343) and from the U.K. Medical Research Council.We thank Dr. Peter J. Parker for his generous gift of PKC, and Yvonne Vallis for her skillful assistance with the cultures and harvesting of the NG108-15 transfected cells.     

Agonist Regulation of Gene Expression of Adrenergic Receptors and G Proteins

Abstract: Study of transmembrane signaling via G proteins has focused to a large extent upon investigations of individual G protein-linked receptor-effector systems. Agonist-induced desensitization and down-regulation of β-adrenergic receptors, for example, have been studied extensively and adopted as a general model for G protein-linked receptor regulation. This review focuses not only on agonist regulation of adrenergic receptor gene expression, but also on how agonists regulate opposing adrenergic receptor-mediated pathways. This important feature of G protein-mediated pathways, i.e., cross-regulation and integration of information among several pathways, will be discussed in the context of what has been learned in the adrenergic receptor-coupled pathways.     

CBP-18, a Ca2+-Binding Protein in Rat Brain: Tissue Distribution and Localization

Abstract: The distribution of a novel calcium-binding protein with a molecular mass of 18 kDa (CBP-18) in the rat brain was studied by means of biochemical methods and immunohistochemistry on cryostat-sectioned tissue and compared with staining patterns of parvalbumin on adjacent sections. The biochemical analysis revealed high levels of CPB-18 in cortex and cerebellum, low levels in the lungs, and undetectable levels in all other tissues tested. Immunohistochemically, the polyclonal rabbit-derived antibody for CPB-18 showed selective affinity with periglomerular cells and dendrites in the olfactory bulb. Distinct immunostaining of scattered cells and their proximal dendrites was found in the anterior olfactory nuclei and in the perirhinal and entorhinal cortex. Strong staining of neuropil with recognizable but diffusely outlined cells was observed in the retrosplenial cortex, central amygdala, hippocampal rudiment, septum, area preoptica, hypothalamus, colliculus superior, and parabrachial nuclei. The cerebellum showed strong neuropil staining of both the molecular and the granule cell layer. Less intense neuropil staining and a few scattered cells were found in the neocortex, the remaining basal forebrain, and in the entire brainstem. Immunoreactivity was barely detectable or missing in the striatum, the hippocampus, the thalamus, and in the colliculus inferior. Thus, CPB-18 shows a unique staining pattern in the CNS, different from all other Ca²⁺-binding proteins studied so far.     

A τ Fragment Containing a Repetitive Sequence Induces Bundling of Actin Filaments

Abstract: Much indirect evidence suggests that the interconnections of actin microfilaments with the microtubule system are mediated by microtubule-associated proteins (MAPs). In this study we provide new data to support the interaction of a specific tubulin-binding domain on τ with actin in vitro. In actin polymerization assays, the synthetic peptide VRSKIGSTENLKHQPGGG, corresponding to the first repetitive sequence of τ protein, increased turbidity at 320 nm in a dose-dependent fashion. A salient feature of the τ peptide-induced assembly process is the formation of a large amount of actin filament bundles, as revealed by electron microscopic analysis. An increase in the τ peptide concentration resulted in a proportional increase in the bundling of actin filaments. It is interesting that a gradual decrease of pH within the range 7.6–4.7 resulted in a higher effect of τ peptide in promoting bundles of actin filaments. A similar pH-dependent effect was observed for τ protein-induced bundling. An analysis of the mechanisms that operate in the peptide induction of actin filament bundles suggests the involvement of electrostatic forces, because the neutralization of ɛ-aminolysyl residues by selective carbamoylation resulted in a complete loss of the peptide induction of actin bundles. The data suggest that a τ repetitive sequence (also found in MAP-2 and MAP-4) containing a common tubulin binding motif may constitute a functional domain on τ for the dynamics of the interconnections between actin filaments and microtu-bules.