Graphene Oxide-Arginine Composites: Efficient Dual Function Materials for Integrated CO2 Capture and Conversion

The "on-demand" capture and utilization of CO2 is effectively realized with a readily accessible dual function organic composite. The covalent and controlled derivatization of graphene oxide (GO) surface with naturally occurring arginine led to a "smart" material capable of capturing (chemisorption) CO2 from high-purity flue-gas as well as low-concentration streams (i. e. direct air capture) and concomitant chemical activation toward the incorporation into cyclic carbonates. The overall integrated CO2 capture and conversion (ICCC) strategy has been fully elucidated mechanistically via dedicated computational, spectroscopic and thermal analyses.

Reductive cyclodimerization of chalcones: exploring the "self-adaptability" of galvanostatic electrosynthesis

The "self-adaptability" of galvanostatic electrolysis was shown to assist a multistage unprecedented chemo- and diastereoselective electrochemically promoted cyclodimerization of chalcones. The process, all involving the reductive events, delivered densely functionalized cyclopentanes featuring five contiguous stereocenters (25 examples, yields of up to 95%, dr values up to >20 : 1). Dedicated and combined experimental as well as electrochemical investigation revealed the key role of a dynamic kinetic resolution of the aldol intermediate for the reaction mechanism.

On the Number of π-Electrons Involved in Stepwise Cycloaddition Reactions

The development of higher-order cycloadditions has mainly been restricted by the requisite usage of highly conjugated and reactive π-systems. Recent years have witnessed organocatalysis as a potent mediator for several of the challenges associated herein, rendering higher-order cycloadditions a legitimate option for achieving the selective construction of specific molecular scaffolds. These developments reinvigorate the efforts to try to understand the underlying principles for cycloadditions involving a higher number of π-electrons than the "classical" cycloadditions; how do we properly address the impact which the addition of further π-electrons have on the reactivity of a system? Herein, computational investigations of two model higher-order cycloaddition systems have been performed to try to provide insights on changes in energetic barriers induced by the presence of benzofusions in a position which is unobstructive to the reactivity. With experimental substantiation as support, these studies might open up for a discussion on whether the π-electrons of benzofused systems simply act as spectator electrons, or play a tangible role on the observed reactivity to an extent where a distinct nomenclature is meritable.

Nickel Catalyzed Carbonylation/Carboxylation Sequence via Double CO2 Incorporation

A carbonylation-carboxylation synthetic sequence, via double CO2 fixation, is described. The productive merger of a Ni-catalyzed cross-electrophile coupling manifold, with the use of AlCl3, triggered a cascade reaction with the formation of three consecutive C-C bonds in a single operation. This strategy traces an unprecedented synthetic route to ketones under Lewis acid assisted carbon dioxide valorization. Computational insights revealed a unique double function of AlCl3, and labeling (13CO2) experiments validate the genuine incorporation of CO2 in both functional groups.

Electrochemical C(sp3)-H functionalization of ethers via hydrogen-atom transfer by means of cathodic reduction

The chemo- and stereoselective electrochemical allylation/alkylation of ethers is presented via a C(sp³)-H activation event. The electrosynthetic protocol enables the realization of a large library of functionalized ethers (35 examples) in high yields (up to 84%) via cathodic activation of a new type of redox-active carbonate (RAC), capable of triggering HAT (Hydrogen-Atom-Transfer) events through the generation of electrophilic oxy radicals. The process displayed high functional group tolerance and mild reaction conditions. A mechanistic elucidation via voltammetric analysis completes the study.

Catalyst and Additive-free Electrochemical CO2 Fixation into Morita-Baylis-Hillman Acetates

The electrochemical carboxylation of Morita-Baylis-Hillman (MBH) acetates with CO2 is presented. The process proceeds in the absence of transition metal catalysts and relies on the cathodic reduction of MBH acetates to generate nucleophilic anions able to trap low-pressure CO2. Valuable succinate derivatives are obtained (20 examples) in high yields (up to 90%) and high functional group tolerance. A remarkable substrate controlled (electronic nature) regioselectivity of the transformation was documented along with a mechanistic rationale based on control experiments.

Recyclable GO-Arginine Hybrids for CO2 Fixation into Cyclic Carbonates

New covalently modified GO-guanidine materials have been realized in a gram-scale synthesis and purified by an innovative microfiltration. The use of these composites in the fixation of CO₂ into cyclic carbonates is demonstrated. Mild operating conditions, high yields (up to 85 %), wide scope (15 examples) and recoverability/reusability (up to 5 cycles) of the material account for the efficiency of the protocol. Dedicated control experiments shed light on the activation modes exerted by GO-l-arginine during the ring-opening/closing synthetic sequence.

Direct Synthesis of α-Aryl-α-Trifluoromethyl Alcohols via Nickel Catalyzed Cross-Electrophile Coupling

A nickel-catalyzed reductive cross-electrophile coupling between the redox-active N-trifluoroethoxyphthalimide and iodoarenes is documented. The protocol reproduces a formal arylation of trifluoroacetaldehyde under mild conditions in high yields (up to 88 %) and with large functional group tolerance (30 examples). A combined computational and experimental investigation revealed a pivotal solvent assisted 1,2-Hydrogen Atom Transfer (HAT) process to generate a nucleophilic α-hydroxy-α-trifluoromethyl C-centered radical for the Csp² -Csp³ bond forming process.

Regio- and Stereoselective Electrochemical Alkylation of Morita-Baylis-Hillman Adducts

Electrosynthesis is effectively employed in a general regio- and stereoselective alkylation of Morita–Baylis–Hillman compounds. The exposition of N-acyloxyphthalimides (redox-active esters) to galvanostatic electroreductive conditions, following the sacrificial-anode strategy, is proved an efficient and practical method to access densely functionalized cinnamate and oxindole derivatives. High yields (up to 80%) and wide functional group tolerance characterized the methodology. A tentative mechanistic sketch is proposed based on dedicated control experiments.

Visible-Light Assisted Covalent Surface Functionalization of Reduced Graphene Oxide Nanosheets with Arylazo Sulfones

We present an environmentally benign methodology for the covalent functionalization (arylation) of reduced graphene oxide (rGO) nanosheets with arylazo sulfones. A variety of tagged aryl units were conveniently accommodated at the rGO surface via visible-light irradiation of suspensions of carbon nanostructured materials in aqueous media. Mild reaction conditions, absence of photosensitizers, functional group tolerance and high atomic fractions (XPS analysis) represent some of the salient features characterizing the present methodology. Control experiments for the mechanistic elucidation (Raman analysis) and chemical nanomanipulation of the tagged rGO surfaces are also reported.

Merging C-C σ-bond activation of cyclobutanones with CO2 fixation via Ni-catalysis

A carboxylative Ni-catalyzed tandem C-C σ-bond activation of cyclobutanones followed by CO₂-electrophilic trapping is documented as a direct route to synthetically valuable 3-indanone-1-acetic acids. The protocol shows an adequate functional group tolerance and useful chemical outcomes (yield up to 76%) when AlCl₃ is adopted as an additive. Manipulations of the targeted cyclic scaffolds and a mechanistic proposal based on experimental evidence complete the investigation.

Organocatalytic Enantioselective Construction of Conformationally Stable C(sp2)-C(sp3) Atropisomers

Nonbiaryl atropisomers are molecules defined by a stereogenic axis featuring at least one nonarene moiety. Among these, scaffolds bearing a conformationally stable C(sp²)-C(sp³) stereogenic axis have been observed in natural compounds; however, their enantioselective synthesis remains almost completely unexplored. Herein we disclose a new class of chiral C(sp²)-C(sp³) atropisomers obtained with high levels of stereoselectivity (up to 99% ee) by means of an organocatalytic asymmetric methodology. Multiple molecular motifs could be embedded in this class of C(sp²)-C(sp³) atropisomers, showing a broad and general protocol. Experimental data provide strong evidence of the conformational stability of the C(sp²)-C(sp³) stereogenic axis (up to t_1/2^25 °C >1000 y) in the obtained compounds and show kinetic control over this rare stereogenic element. This, coupled with density functional theory calculations, suggests that the observed stereoselectivity arises from a Curtin-Hammett scenario establishing an equilibrium of intermediates. Furthermore, the experimental investigation led to evidence of the operating principle of central-to-axial chirality conversions.

Convenient synthesis of tricyclic N(1)-C(2)-fused oxazino-indolones via [Au(I)] catalyzed hydrocarboxylation of allenes

A new [Au(I)] catalyzed intramolecular hydrocarboxylation of allenes is presented as a valuable synthetic route to oxazino-indolones. The employment of 3,5-(CF3)2-C6H3-ImPyAuSbF6 as the optimal catalyst (5 mol%) was necessary to...

NiNP@rGO Nanocomposites as Heterogeneous Catalysts for Thiocarboxylation Cross-Coupling Reactions

A new type of ligand-free Ni-nanoparticles supported on rGO (size distribution average d = 9 ± 3 nm) was prepared and fully characterized via morphological (Fe-SEM), structural (P-XRD, HR-TEM), and spectroscopic (ICP-EOS, XPS) analysis tools. The metal composite was effectively employed in the unprecedented heterogeneously Ni-assisted cross-coupling reaction of aryl/vinyl iodides and thiocarboxylates. A range of sulfur-containing aryl as well as vinyl derivatives (15 examples) was achieved in high yields (up to 82%), under mild reaction conditions, and with wide functional group tolerance.

Aminocatalytic [8+2] Cycloaddition Reactions toward Chiral Cyclazines

An efficient and exceptionally stereoselective synthesis of chiral cycl[3.2.2]azines has been realized by means of the rational design and utilization of novel (E)-3-benzylidene-3H-pyrrolizines in iminium-ion-catalyzed [8+2] cycloaddition reactions. The presented protocol allows for the incorporation of diverse enals, including cinnamaldehydes, enolizable aldehydes, and substrates of extended conjugation. The obtained products contain both an electron-rich alkenyl pyrrole moiety and an electron-deficient carbaldehyde substituent, and both moieties can undergo selective transformations with retention of the stereochemical information established in the [8+2] cycloaddition.

Enantioselective Construction of the Cycl[3.2.2]azine Core via Organocatalytic [12 + 2] Cycloadditions

The first enantioselective [12 + 2] cycloaddition has been developed for the construction of a chiral cycl[3.2.2]azine core, a tricyclic moiety with a central ring-junction nitrogen atom, by an operationally simple one-step organocatalytic process. The reaction concept builds upon aminocatalytically generated 12π-components derived from 5H-benzo[a]pyrrolizine-3-carbaldehydes reacting with different electron-deficient 2π-components and affording the complex scaffold of benzo[a]cycl[3.2.2]azine (indolizino[3,4,5-ab]isoindole) with excellent enantio- and diastereoselectivity in good yields. The developed reaction is robust toward diverse substituent patterns and has been extended to different classes of electron-deficient 2π-components by minor variations in reaction setup. The obtained [12 + 2] cycloadducts are electron-deficient in nature, and their reaction with nucleophiles have been demonstrated. The enantioselective [12 + 2] cycloaddition with α,β-unsaturated aldehydes as the electron-deficient 2π-components relies upon an unconventional, simple aminocatalyst. In order to understand the high stereoselectivity of the [12 + 2] cycloaddition for this simple catalyst, combined experimental and computational investigations were performed. The investigations point to activation of both the 5H-benzo[a]pyrrolizine-3-carbaldehyde and the α,β-unsaturated aldehyde by the aminocatalyst and that the reaction proceeds by a stepwise cycloaddition, where especially the ring-closure is crucial for the stereochemical outcome. For other electron-deficient 2π-components, such as α,β-unsaturated ketoesters and nitroolefins, a more sterically demanding aminocatalyst has been applied and the corresponding [12 + 2] cycloadducts are obtained with excellent stereoselectivity. The [12 + 2] cycloaddition with vinyl sulfones afforded fully unsaturated systems, which display photoluminescence properties and for which quantum yields have been evaluated.

Organocatalytic Enantioselective 1,3-Dipolar [6+4] Cycloadditions of Tropone

A highly stereoselective 1,3-dipolar [6+4] cycloaddition towards bridged azabicyclo[4.3.1]decane scaffolds has been developed, reacting aldehydes, 2-aminomalonates and tropone under mild conditions in the presence of a chiral phosphoric acid catalyst. The scope is demonstrated for a series of aldehydes and 2-aminomalonates, and the reaction proceeds in high yields, >95:5 d.r. and up to 99 % ee. A series of transformations, as well as a mechanistic proposal, are presented.

Organocatalytic Asymmetric Methodologies towards the Synthesis of Atropisomeric N-Heterocycles

A perspective on the literature dealing with the organocatalytic asymmetric preparation of axially chiral N-heterocycles is provided. A particular focus is devoted to rationalize the synthetic strategies employed in each case. Moreover, specific classes of organocatalysts are shown to stand out as privileged motives for the stereoselective preparation of such synthetically challenging molecular architectures. Finally, an overview of the main trends in the field is given.

1 Introduction

2 Five-Membered Rings

2.1 Arylation

2.2 Dynamic Kinetic Resolution

2.3 Ring Construction

2.4 Central-to-Axial Chirality Conversion and Chirality Transfer

2.5 Desymmetrization

3 Six-Membered Rings

3.1 Desymmetrization

3.2 (Dynamic) Kinetic Resolution

3.3 Ring Construction

3.4 Central-to-Axial Chirality Conversion

4 Conclusion

Quinone-Fused Pyrazoles through 1,3-Dipolar Cycloadditions: Synthesis of Tricyclic Scaffolds and in vitro Cytotoxic Activity Evaluation on Glioblastoma Cancer Cells

A novel and straightforward synthesis of highly substituted isoquinoline-5,8-dione fused tricyclic pyrazoles is reported. The key step of the synthetic sequence is a regioselective, Ag₂ CO₃ promoted, 1,3-dipolar cycloaddition of C-heteroaryl-N-aryl nitrilimines and substituted isoquinoline-5,8-diones. The broad functional group tolerability and mild reaction conditions were found to be suitable for the preparation of a small library of compounds. These scaffolds were designed to interact with multiple biological residues, and two of them, after brief synthetic elaborations, were analyzed by molecular docking studies as potential anticancer drugs. In vitro studies confirmed the potent anticancer effects, showing promising IC₅₀ values as low as 2.5 μm against three different glioblastoma cell lines. Their cytotoxic activity was finally positively correlated to their ability to inhibit PI3K/mTOR kinases, which are responsible for the regulation of diverse cellular processes in human cancer cells.

An organocatalytic enantioselective direct α-heteroarylation of aldehydes with isoquinoline N-oxides

A new protocol for the enantioselective direct α-heteroarylation of aldehydes with isoquinoline N-oxides, via chiral enamine catalysis, has been successfully developed. High enantiomeric excesses and moderate to good yields were achieved for a variety of α-heteroarylated aldehydes.

Nucleophilic Dearomatization of Pyridines under Enamine Catalysis: Regio-, Diastereo-, and Enantioselective Addition of Aldehydes to Activated N-Alkylpyridinium Salts

Catalytic addition of chiral enamines to azinium salts is a powerful tool for the synthesis of enantioenriched heterocycles. An unprecedented asymmetric dearomative addition of aldehydes to activated N-alkylpyridinium salts is presented. The process exhibits complete C-4 regioselectivity along with high levels of diastereo- and enantiocontrol, achieving a high-yielding synthesis of a broad range of optically active 1,4-dihydropyridines. Moreover, the presented methodology enables the synthesis of functionalized octahydropyrrolo[2,3-c]pyridines, the core structure of anticancer peptidomimetics.

Radiofrequency treatments: what can we expect?

Among non-ablative procedures in aesthetic medicine, the radiofrequency (RF) is one of the most popular for the treatment of face and body skin laxity. It can be classified as a physical bio-stimulation that produces a temperature increase on biological structures, using electromagnetic waves. The term encompasses devices having substantial differences in energy, wavelengths, handpieces dimension and structure. Moreover, for some of these, the protocols are only partially defined. The aim of this short review is to clarify some aspecst of the RF therapy starting from the physics, passing through the mechanism of action and finally, with the most suitable protocols. Contrary to mechanic waves, electromagnetic waves, physics are always transversal to the impulse and this leads to the different energy distribution in capacitive (monopolar) or resistive (bi- or multi-polar) applications. The thermal damage as therapeutic effect is a postulate that needs to be discussed and the same is true for the terms “non-surgical” and “non-ablative”, often recurrent in the scientific literature. Protocols must be optimized according to the machine and the patient, keeping in mind the possibilities of biostimulation in terms of immediate improvement and of long lasting investment in skin rejuvenation. It is mandatory to understand the possibilities and limitations of each device to perform useful, safe and correct medical treatments.

THE THEORIES OF AGING: REACTIVE OXYGEN SPECIES AND WHAT ELSE?

This manuscript is a short review on the theories of aging, focusing mainly on the balance between the nutrient and the oxygen intake necessary for energy metabolism and the processes for neutralizing the negative consequences of energy production. The first section entitled “Why” provides brief historical details regarding the main group of aging theories, firstly the evolutionary theories and secondly the theories of aging related to humans, cells and biomolecules are discussed. The second section entitled ‘Where’ includes brief summaries of the many cellular levels at which aging damage can occur: replicative senescence with its genetic and epigenetic implications, cytoplasmic accumulation, mitochondrial respiratory chain dysfunction, peroxisome and membrane activity. In the third section entitled ‘How’ the linking mechanisms between the caloric restriction and the antioxidant intake on lifespan and aging in experimental models are discussed. The role of ROS is evaluated in relation to the mitochondria, the AMPK activated sirtuins, the hormesis, the target of rapamicin and the balance autophagy/apoptosis.

HYALURONIC ACID: THE USE OF ITS PRECURSOR IN SKIN BIO-STIMULATION

Bio-stimulation is an injective therapy aimed to boost the anabolic functions of dermal fibroblasts to obtain skin improvement. It can be achieved with multiple intradermal injections (0.05–0.1 ml each) of a solution of 400 mg (3 ml) of injectable glucosamine sulphate, plus 5.623 mg (3 ml) of polideoxyribonucleotide, 1 ml of lidocaine and 0.5–1 ml of sodium bicarbonate, to repeat every 7, 14, 21, and 28 days. The administration of glucosamine sulphate to skin fibroblasts is believed to lead to its incorporation in glycosaminoglycans, and thereby to the stimulation of extracellular matrix synthesis, whereas polideoxyribonucleotide possesses anti-inflammatory and regenerative capability. This study aims to elucidate the in-vitro effects of this treatment by studying what happens to several genes related to connective tissue integrity. Human dermal fibroblasts were seeded in a culture medium enriched with either two drugs alone or combined: glucosamine sulphate and/or polideoxyribonucleotide. After the end of the exposure time of 24 h, 48 h, and 72 h, the cells were trypsinized and lysed for RNA extraction. Reverse transcription to cDNA was performed directly from cultured cell lysate. Finally, the cDNA was amplified by real-time PCR and a panel of genes involved in dermal integrity was tested. Gene expression of Hyaluronan synthase 1 (HAS1), Elastine (ELN), Insulin like growth factor 1 (IGF1), Growth differentiation factor 6 (GDF6) and of a series of catabolic enzymes, such as Metalloproteases (MMP) 2, 3 and 13, the neutrophyl expressed Elastase (ELANE) and the Hyaluronidase 1 (HYAL1) were tested after 24, 48 and 72 hours of exposure to glucosamine sulphate and polideoxyribonucleotide alone or combined. All the tested genes but one were up-regulated. A negative synergism on several enzymes (particularly appreciable for Insulin-like growth factor 1 and metalloprotease 13) was observed when the two drugs were delivered together. Glucosamine sulphate acts not only as building block in the biosynthesis of glycosaminoglycan chains, but also as a booster of hyaluronan synthase 1. The association of glucosamine sulphate and polideoxyribonucleotide, used in bio-stimulation therapy protocol, has a negative synergism on catabolic genes in dermal fibroblast cultures. The present observations produce further insight into the effects of glucosamine sulphate in the biosynthesis of glycosaminoglycan chains.

Role of antioxidants in dermal aging: an in vitro study by q-RT-PCR

BACKGROUND

Reactive oxygen species production is the final step in skin aging. These unstable molecules can damage and destroy DNA, proteins, and membrane phospholipids. The aim of this study was to test the in vitro effect of an antioxidant precursor, N-acetylcysteine (NAC), on human dermal fibroblasts. NAC alone and a solution of NAC and amino acids together, used in aesthetic medicine as intradermal injection treatment, were tested.

METHODS

The expression levels of some connective related genes (HAS1, HYAL1, ELN, ELANE, DSP, GDF6, and IGF1) were analyzed on cultures of dermal fibroblasts using real-time reverse-transcription polymerase chain reaction (real time RT-PCR).

RESULTS

All genes were upregulated after 24 h of treatment.

CONCLUSIONS

An interesting effect of gene induction by administration of NAC and amino acids in vitro was demonstrated. Upregulation of elastin-, hyaluronic acid-, and GDF6-encoding genes supports the evidence of clinical improvement induced by NAC biostimulation in the prevention and correction of skin aging.

Immunochemical localization of calcium/calmodulin-dependent protein kinase I

Ca2+/calmodulin-dependent protein kinase I (CaM kinase I) was originally identified in rat brain based on its ability to phosphorylate site 1 of synapsin I. Recently a cDNA for the rat brain enzyme has been cloned and the primary structure elucidated [Picciotto et al. (1993), J. Biol. Chem., 268:26512-26521]. The rat cDNA encoded a protein of 374 amino acids with a calculated M(r) of 41,636. Antibodies have now been raised against the recombinant kinase expressed in E. coli as a glutathione-S-transferase fusion protein. Immunoblot analysis of rat cortex lysates revealed two major immunoreactive bands of approximately M(r) 38,000 and 42,000. Minor immunoreactive species of slightly lower M(r) were also detected. Two distinct CaM kinase I activities were partially purified from rat brain and shown to correspond to the two major immunoreactive species. A variety of immunoreactive species of M(r) 35-43,000 were detected in "brain" tissue from cow, zebra finch, goldfish, Xenopus, lamprey, and Drosophila. In rat brain, immunocytochemistry revealed strong staining in cortex, hippocampus, amygdala, hypothalamus, brain stem, and choroid plexus. The labelling was mainly observed in neuropil but clusters of intensely labelled neuronal cell bodies were also detected all along the neuraxis. Neuronal nuclei and glial cells did not appear to be stained. Subcellular fractionation studies confirmed the cytosolic localization of the kinase in the brain. In various rat non-neuronal tissues and in a number of cell lines, immunoreactive species of approximately M(r) 38,000 and approximately 42,000 were detected at lower levels than that detected in brain. The M(r) 38,000 and 42,000 species were also found in different ratios and at different levels in the non-neuronal tissues. These results support a role for CaM kinase I in the regulation of multiple neuronal processes. Furthermore, the widespread cell and tissue distribution suggests that CaM kinase I may function as a ubiquitous multi-functional protein kinase. Finally, the multiple immunoreactive species may represent isoforms of CaM kinase I.

Distribution of protein phosphatase inhibitor-1 in brain and peripheral tissues of various species: comparison with DARPP-32

The distribution of inhibitor-1, a cyclic AMP-regulated inhibitor of protein phosphatase-1, was analyzed in various brain regions and peripheral tissues of various species by immunolabeling of sodium dodecyl sulfate-poly-acrylamide gel transfers using specific antibodies. The distribution of inhibitor-1 was directly compared to that of DARPP-32, a structurally related cyclic AMP-regulated inhibitor of protein phosphatase-1. In rat CNS, a single immunoreactive protein of M(r) 30,000, identified as inhibitor-1, was widely distributed. In contrast, DARPP-32 was highly concentrated in the basal ganglia. Inhibitor-1 was detected in brain tissue from frog (M(r) 27,000), turtle (M(r) 29,000/33,000), canary (M(r) 26,000), pigeon (M(r) 28,000), mouse (M(r) 30,500), rabbit (M(r) 26,500), cow (M(r) 27,000), and monkey (M(r) 27,500), but not from goldfish. Inhibitor-1 was detected at various levels in most peripheral tissues of the species studied; however, it was not detectable in certain tissues of particular species (e.g., rat and cow liver). DARPP-32 was detected in brain tissue of all the species tested except frog and goldfish, but was not detectable in most peripheral tissues. Both inhibitor-1 and DARPP-32 were concentrated in the cytosol and synaptosomal cytosol of rat striatum. The developmental expressions of inhibitor-1 and DARPP-32 in rat striatum differed: the level of inhibitor-1 peaked in the first postnatal week and then declined by the third postnatal week, whereas the level of DARPP-32 increased to a peak level by the third postnatal week and remained elevated thereafter.(ABSTRACT TRUNCATED AT 250 WORDS)

Phosphorylation of the cystic fibrosis transmembrane conductance regulator

Regulation of epithelial chloride flux, which is defective in patients with cystic fibrosis, may be mediated by phosphorylation of the cystic fibrosis transmembrane conductance regulator (CFTR) by cyclic AMP-dependent protein kinase (PKA) or protein kinase C (PKC). Part of the R-domain of CFTR (termed CF-2) was expressed in and purified from Escherichia coli. CF-2 was phosphorylated on seryl residues by PKA, PKC, cyclic GMP-dependent protein kinase (PKG), and calcium/calmodulin-dependent protein kinase I (CaM kinase I). Direct amino acid sequencing and peptide mapping of CF-2 revealed that serines 660, 700, 737, and 813 as well as serine 768, serine 795, or both were phosphorylated by PKA and PKG, and serines 686 and 790 were phosphorylated by PKC. CFTR was phosphorylated in vitro by PKA, PKC, or PKG on the same sites that were phosphorylated in CF-2. Kinetic analysis of phosphorylation of CF-2 and of synthetic peptides confirmed that these sites were excellent substrates for PKA, PKC, or PKG. CFTR was immunoprecipitated from T84 cells labeled with 32Pi. Its phosphorylation was stimulated in response to agents that activated either PKA or PKC. Peptide mapping confirmed that CFTR was phosphorylated at several sites identified in vitro. Thus, regulation of CFTR is likely to occur through direct phosphorylation of the R-domain by protein kinases stimulated by different second messenger pathways.

Protein phosphotyrosine in mouse brain: developmental changes and regulation by epidermal growth factor, type I insulin-like growth factor, and insulin

Using antiphosphotyrosine antibodies, we have investigated protein phosphorylation in mouse brain during development in intact animals and in reaggregated cerebral cultures. Under basal conditions, in vivo and in vitro, the levels of two main phosphoproteins, of Mr 120,000 and 180,000 (pp180), increased with development, reaching a maximum in the early postnatal period and decreasing thereafter. In adult forebrain, pp180 was still highly phosphorylated, but it was not detected in cerebellum or in peripheral tissues. In reaggregated cortical cultures, epidermal growth factor (EGF), type I insulin-like growth factor (IGF-I), and insulin enhanced protein tyrosine phosphorylation of several proteins, which were specific for EGF or IGF-I/insulin. In highly enriched neuronal or astrocytic monolayer cultures, some proteins phosphorylated in basal conditions, or in response to EGF and IGF-I, were found in both types of culture, whereas others appeared cell type specific. In addition, in each cell type, some proteins were phosphorylated under the action of both growth factors. These results indicate that tyrosine protein phosphorylation is maximal in mouse brain during development and is regulated by growth factors in neurons as well as in astrocytes.