Synthesis of Perdeuterated Alkyl Amines/Amides with Pt/C as Catalyst under Mild Conditions.

A convenient method for the synthesis of perdeuterated alkyl amides/amines is disclosed. Perdeuterated acetyl amides can be achieved by a hydrogen-deuterium (H/D) exchange protocol with Pt/C as a catalyst and D2O as a deuterium source under mild conditions. After removal or reduction of the acetyl group, this protocol can provide perdeuterated primary, secondary, and tertiary amines, which are difficult to achieve via other methods.

Revealing the Marine Cycles of Volatile Sulfur Compounds and Their Biogeochemical Controls: A Case of the Western North Pacific.

Volatile sulfur compounds, such as dimethyl sulfide (DMS), carbonyl sulfide (OCS), and carbon disulfide (CS2), have significant implications for both atmospheric chemistry and climate change. Despite the crucial role of oceans in regulating their atmospheric budgets, our comprehension of their cycles in seawater remains insufficient. To address this gap, a field investigation was conducted in the western North Pacific to clarify the sources, sinks, and biogeochemical controls of these gases in two different marine environments, including relatively eutrophic Kuroshio-Oyashio extension (KOE) and oligotrophic North Pacific subtropical gyre. Our findings revealed higher concentrations of these gases in both seawater and the atmosphere in the KOE compared to the subtropical gyre. In the KOE, nutrient-rich upwelling stimulated rapid DMS biological production, while reduced seawater temperatures hindered the removal of OCS and CS2, leading to their accumulation. Furthermore, we have quantitatively evaluated the relative contribution of each pathway to the source and sink of DMS, OCS, and CS2 within the mixed layer and identified vertical exchange as a potential sink in most cases, transporting substantial amounts of these gases from the mixed layer to deeper waters. This research advances our understanding of sulfur gas source-sink dynamics in seawater, contributing to the assessment of their marine emissions and atmospheric budgets.

Important Roles and Formation of Atmospheric Organosulfates in Marine Organic Aerosols: Influence of Phytoplankton Emissions and Anthropogenic Pollutants.

Organosulfates (OSs) could be potentially important compounds in marine organic aerosols, while their formation in marine atmospheres is far from clear due to a lack of cruise observations. In this work, shipboard atmospheric observations were conducted over the Yellow Sea and Bohai Sea to investigate the abundance and formation of biogenic isoprene/monoterpene-OSs in marine aerosols. The quantified OSs and NOSs accounted for 0.04-6.9% of marine organic aerosols and were 0.07-2.2% of the non-sea-salt (nss) sulfate in terms of sulfur content. Isoprene-related (nitrooxy-)OSs occupied 27-87% of the total quantified OSs, following the abundance order of summer > autumn > spring or winter. This order was driven by the marine phytoplankton biomass and sea surface temperature (SST), which controlled the seawater and atmospheric isoprene concentration levels. Under the severe impacts of anthropogenic pollutants from the East Asia continent in winter, monoterpene nitrooxy-OSs, generated with NOx involved in, increased to 34.4 ± 35.5 ng/m3 and contributed 68% of the quantified (nitrooxy-)OSs. Our results highlight the notable roles of biogenic OSs in marine organic aerosols over regions with high biological activity and high SST. The formation of biogenic OSs and their roles in altering marine aerosol properties calls for elaboration through cruise observations in different marine environments.

Biogeochemical controls on climatically active gases and atmospheric sulfate aerosols in the western Pacific.

The Pacific Ocean plays an important role in regulating the budget of climatically active gases and the burden of sulfate aerosols. Here, a field investigation was conducted to clarify the key processes and factors controlling climatically active gases, including dimethyl sulfide (DMS), carbonyl sulfide (OCS), carbon disulfide (CS2), and carbon dioxide (CO2), in both surface seawater and the lower atmosphere of the western Pacific. In addition, the relative contributions of different sources to atmospheric sulfate aerosols were quantitatively estimated, and their causes were explored. The maximum concentrations of DMS, OCS and CS2 and the minimum partial pressure of CO2 (pCO2) were observed in the Kuroshio-Oyashio Extension. Kuroshio-induced mesoscale eddies brought abundant nutrients and organic matter from the subsurface layer of Oyashio into the euphotic layer, thus enhancing primary productivity and accelerating the photoreaction of organic matter. These processes led to higher concentrations of DMS, OCS and CS2 and lower pCO2. However, the oligotrophic subsurface layer in the subtropical gyre and the strong barrier layer in the equatorial waters suppressed the upward fluxes of nutrients and organic matter, resulting in lower surface concentrations of DMS, OCS, and CS2 in these areas. Being far from the continents, atmospheric concentrations of DMS, OCS and CS2 and pCO2 in the western Pacific generally were observed to depend on the local sea-to-air exchange and may be regulated by atmospheric oxidation and mixing of air masses. In general, oceanic DMS emissions played an important role in the formation of sulfate aerosols in the western Pacific (accounting for ∼19.5% of total sulfate aerosols), especially in the Kuroshio-Oyashio Extension (∼32.3%). These processes in seawater may also determine the variations and emissions of other climatically active gases from biogenic and photochemical sources.

Synthesis of ß-Deuterated Amino Acids via Palladium-Catalyzed H/D Exchange.

Despite several synthetic approaches that have been developed for α-deuterated amino acids, the synthesis of ß-deuterated amino acids has remained a challenge. Herein, we disclose a palladium catalyzed H/D exchange protocol for a ß-deuterated N-protected amino amide, which can be converted to a ß-deuterated amino acid simply by removal of protecting groups. This protocol is highly efficient, simply manipulated, and appliable for deuterium-labeling of many amino amides. In addition, deuterium labeling of phenylalanine derivatives was also successful when pivalic acid served as an additive to promote the H/D exchange process.

Silver salt enabled H/D exchange at the ß-position of thiophene rings: synthesis of fully deuterated thiophene derivatives.

We disclose a silver catalyzed H/D exchange reaction, which can introduce the deuterium atom at the ß position of thiophene rings without the assistance of any coordinating groups. The advantages of this reaction include operation in open air, usage of D2O as the deuterium source, good tolerance to a range of functional groups and obtaining high atom% deuterium incorporation. In addition, this H/D exchange reaction is employed for direct deuteration of a thiophene based monomer, which is usually prepared by multistep synthesis from expensive deuterated starting materials.

Ag(i)-Mediated hydrogen isotope exchange of mono-fluorinated (hetero)arenes.

An efficient approach to install deuterium into mono-fluorinated (hetero)arenes by a Ag2CO3/Sphos-mediated HIE protocol with D2O as the deuterium source has been disclosed. This method showed a specific site selectivity of deuteration at the α-position of the fluorine atom, which is complementary to the existing transition metal-catalyzed HIE process.

Molecular insight into bacterial cleavage of oceanic dimethylsulfoniopropionate into dimethyl sulfide.

The microbial cleavage of dimethylsulfoniopropionate (DMSP) generates volatile DMS through the action of DMSP lyases and is important in the global sulfur and carbon cycles. When released into the atmosphere from the oceans, DMS is oxidized, forming cloud condensation nuclei that may influence weather and climate. Six different DMSP lyase genes are found in taxonomically diverse microorganisms, and dddQ is among the most abundant in marine metagenomes. Here, we examine the molecular mechanism of DMSP cleavage by the DMSP lyase, DddQ, from Ruegeria lacuscaerulensis ITI_1157. The structures of DddQ bound to an inhibitory molecule 2-(N-morpholino)ethanesulfonic acid and of DddQ inactivated by a Tyr131Ala mutation and bound to DMSP were solved. DddQ adopts a ß-barrel fold structure and contains a Zn(2+) ion and six highly conserved hydrophilic residues (Tyr120, His123, His125, Glu129, Tyr131, and His163) in the active site. Mutational and biochemical analyses indicate that these hydrophilic residues are essential to catalysis. In particular, Tyr131 undergoes a conformational change during catalysis, acting as a base to initiate the ß-elimination reaction in DMSP lysis. Moreover, structural analyses and molecular dynamics simulations indicate that two loops over the substrate-binding pocket of DddQ can alternate between "open" and "closed" states, serving as a gate for DMSP entry. We also propose a molecular mechanism for DMS production through DMSP cleavage. Our study provides important insight into the mechanism involved in the conversion of DMSP into DMS, which should lead to a better understanding of this globally important biogeochemical reaction.

Quantitative Proteomics Analysis of VEGF-Responsive Endothelial Protein S-Nitrosylation Using Stable Isotope Labeling by Amino Acids in Cell Culture (SILAC) and LC-MS/MS.

Adduction of a nitric oxide moiety (NO•) to cysteine(s), termed S-nitrosylation (SNO), is a novel mechanism for NO to regulate protein function directly. However, the endothelial SNO-protein network that is affected by endogenous and exogenous NO is obscure. This study was designed to develop a quantitative proteomics approach using stable isotope labeling by amino acids in cell culture for comparing vascular endothelial growth factor (VEGFA)- and NO donor-responsive endothelial nitroso-proteomes. Primary placental endothelial cells were labeled with "light" (L-(12)C6 (14)N4-Arg and L-(12)C6 (14)N2-Lys) or "heavy" (L-(13)C6 (15)N4-Arg and L-(13)C6 (15)N2-Lys) amino acids. The light cells were treated with an NO donor nitrosoglutathione (GSNO, 1 mM) or VEGFA (10 ng/ml) for 30 min, while the heavy cells received vehicle as control. Equal amounts of cellular proteins from the light (GSNO or VEGFA treated) and heavy cells were mixed for labeling SNO-proteins by the biotin switch technique and then trypsin digested. Biotinylated SNO-peptides were purified for identifying SNO-proteins by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Ratios of light to heavy SNO-peptides were calculated for determining the changes of the VEGFA- and GSNO-responsive endothelial nitroso-proteomes. A total of 387 light/heavy pairs of SNO-peptides were identified, corresponding to 213 SNO-proteins that include 125 common and 27 VEGFA- and 61 GSNO-responsive SNO-proteins. The specific SNO-cysteine(s) in each SNO-protein were simultaneously identified. Pathway analysis revealed that SNO-proteins are involved in various endothelial functions, including proliferation, motility, metabolism, and protein synthesis. We collectively conclude that endogenous NO on VEGFA stimulation and exogenous NO from GSNO affect common and different SNO-protein networks, implicating SNO as a critical mechanism for VEGFA stimulation of angiogenesis.

S-nitrosylation of Cofilin-1 Serves as a Novel Pathway for VEGF-Stimulated Endothelial Cell Migration.

Nitric oxide (NO) derived from endothelial NO synthase (eNOS) mediates vascular endothelial growth factor (VEGF)-stimulated endothelial cytoskeleton remodeling and migration; however, the underlying mechanisms are elusive. Covalent adduction of a NO moiety (NO(•)) to cysteines called S-nitrosylation (SNO) is a key NO signaling pathway. The small actin-binding protein cofilin-1 (CFL1) is essential for actin cytoskeleton remodeling. We investigated whether S-nitrosylation regulates CFL1 function and endothelial cytoskeleton remodeling and migration upon VEGF stimulation. VEGF rapidly stimulated S-nitrosylation of CFL1, which was blocked by NO Synthase inhibition and eNOS knockdown by specific eNOS-siRNA. Cys80 and Cys139 were identified as the major SNO-sites in CFL1 by LC-MS/MS. The actin severing activity of recombinant SNO-mimetic CFL1 (C80/139A DMA-CFL1), but not SNO-deficient CFL1 (C80/139S DMS-CFL1), was significantly greater than that of wild-type CFL1 (wt-CFL1). When wt-CFL1 and its mutants were overexpressed in endothelial cells, basal actin bound wt-CFL1 was undetectable but significantly increased by VEGF; basal actin bound DMA-CFL1 was readily high and basal actin bound DMS-CFL1 was detectable but low, and both were unresponsive to VEGF. Treatment with VEGF significantly increased filamentous (F-) actin and filopodium formation and cell migration in endothelial cells. Overexpression of wt-CFL1 inhibited VEGF-induced F-actin formation. Overexpression of DMA but not DMS CFL1 decreased basal but not VEGF-stimulated F-actin formation. Overexpression of DMA but not DMS CFL1 suppressed VEGF-stimulated filopodium formation and migration in endothelial cells. Thus, S-nitrosylation of CFL1 provides a novel signaling pathway post-NO biosynthesis via eNOS-derived NO for endothelial cytoskeleton remodeling and migration upon VEGF stimulation.

Alpha 7 nicotinic acetylcholine receptor agonist GTS-21 mitigates isoflurane-induced cognitive impairment in aged rats.

BACKGROUND: Postoperative cognitive dysfunction is increasingly recognized as an important clinical syndrome. Inhalation anesthetics are commonly used during surgery, and it has been proposed that inhalation anesthetics impair cognitive function. However, there are few clinical interventions and treatments available to prevent this disorder. GTS-21, a selective agonist of alpha 7 nicotinic acetylcholine receptor, has been indicated to exert neuroprotective effects in the experimental animal models of neurodegenerative diseases. Therefore, we hypothesized that pretreatment with GTS-21 attenuates isoflurane-induced cognitive decline in aged rats. METHODS: In the present study, 20-mo-old rats were administered GTS-21 or an equal volume of saline by intraperitoneal injection 30 min before exposure to isoflurane. Then the rats were exposed to 1.3% isoflurane for 4 h. Spatial learning and memory of the rats were assessed at 2 wk after isoflurane exposure. The expression levels of interleukin (IL)-1ß, IL-6, and tumor necrosis factor-α in the hippocampus and cerebral cortex were determined by enzyme-linked immunosorbent assay. Simultaneously, neuronal apoptosis in the hippocampus was also observed by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) staining and Nissl staining. RESULTS: We found that exposure to isoflurane induces learning and memory deficits of old rats. IL-1ß in the hippocampus was increased at 4 h after isoflurane exposure. Isoflurane also increased neuroapoptosis in the hippocampus and decreased neuronal density in the CA1 region. And GTS-21 pretreatment effectively alleviated these changes. CONCLUSIONS: The study demonstrated that pretreatment with α7 nicotinic acetylcholine receptor agonist GTS-21 attenuates isoflurane-induced learning and memory impairment in aged rats.

tBu3P-Coordinated 2-Phenylaniline-Based Palladacycle Complex As Precatalyst for Pd-Catalyzed Coupling Reactions of Aryl Halides with Polyfluoroarenes via C-H Activation Strategy.

tBu3P-Coordinated 2-phenylaniline-based palladacycle complex was demonstrated to be an efficient precatalyst for Pd-catalyzed coupling reactions of aryl halides with polyfluoroarenes via C-H activation strategy. The readily accessibility and easy handling nature of tBu3P- coordinated 2-aminobiphenyl-based palladacycle complex and the high yields of the reaction makes tBu3P-coordinated 2-aminobiphenyl-based palladacycle complex an attractive precatalyst for the cross-coupling reaction of aryl halides with polyfluoroarenes.

Sorption characteristics of phosphorus on marine sediments in the presence of black carbon derived from fly ash.

The sorption behavior of phosphorus on marine sediments in the presence of black carbon derived from fly ash (FC) was studied. For both the FC and sediment samples, the kinetic curves could be described by a two-compartment first order equation, and the isotherms fit the Freundlich and Langmuir models well. The high specific surface area with abundant acidic functional groups of FC promoted the sorption and make this process more irreversible. The effects were more significant with higher amount of FC added. After sorption, more significant increase in Ex-P, Fe/Al-P and CaP was found in the sediment with FC added, while the organic groups in FC rarely react with phosphorus to form OP. The pH of medium influenced the sorption character, and FC promoted the process significantly at pH < pHPZNPC. The sorption was endothermic with an increase in randomness. The presence of FC had little effects on the thermodynamic parameters.

K2CO3/18-Crown-6-Catalyzed Selective H/D Exchange of Heteroarenes with Bromide as a Removable Directing Group.

The K2CO3/18-crown-6-catalyzed H/D exchange of heretoarenes in high atom % deuterium incorporation is disclosed. The use of a weak base as a catalyst leads to excellent site selectivity and broad functional group tolerance. Control experiments indicated that the use of bromide, which enhances the adjacent C-H bond reactivity, as a removable directing group is essential. Moreover, conversion of bromide to other functional groups is also performed to construct other useful deuterated compounds.

Characteristics and emissions of isoprene and other non-methane hydrocarbons in the Northwest Pacific Ocean and responses to atmospheric aerosol deposition.

Field investigations in the Northwest Pacific Ocean were carried out to determine the distributions of marine and atmospheric non-methane hydrocarbons (NMHCs), sources and environmental effects. We also conducted deck incubation experiments to investigate the effects of atmospheric aerosol deposition on NMHCs production. The marine NMHCs displayed an increasing trend from the South Equatorial Current to the Oyashio Current. The enhanced phytoplankton biomass and dissolved organic materials (DOM) content in the Kuroshio-Oyashio Extension contributed significantly to isoprene and NMHCs production compared with those in tropical waters and the North Pacific subtropical gyre. The Northwest Pacific Ocean was a significant source of atmospheric NMHCs, with average sea-to-air fluxes of 28.0 ± 38.9, 65.2 ± 73.3, 21.0 ± 26.7, 48.7 ± 62.6, 12.7 ± 15.9, 14.2 ± 16.8, and 41.7 ± 80.4 nmol m-2 d-1 for ethane, ethylene, propane, propylene, i-butane, n-butane, and isoprene, respectively. Influenced by seawater release and OH radical consumption, the atmospheric NMHCs apart from isoprene displayed upward trends with increasing latitude. The deck incubation showed that the addition of aerosols and acidic aerosols significantly boosted phytoplankton biomass, altered community structure, and accelerated the production of isoprene. However, the other six NMHCs showed no obvious responses to atmospheric aerosol deposition in the incubation experiments. In summary, ocean current movements and atmospheric deposition could influence the production and release of isoprene in the Northwest Pacific Ocean.

Contrasting effects of different light regimes on the photoreactivities of allochthonous and autochthonous chromophoric dissolved organic matter.

Chromophoric dissolved organic matter (CDOM) plays an important role in ultraviolet (UV) light absorption in the ocean. CDOM is known to originate from either an allochthonous or autochthonous source and has varying compositions and levels of reactivity; however, the effects of individual radiation treatments and the combined effects of UVA and UVB on allochthonous and autochthonous CDOM remain poorly understood. Thus, here, we measured changes in the common optical properties of CDOM collected from China's marginal seas and the Northwest Pacific, using full-spectrum, UVA (315-400 nm), and UVB (280-315 nm) irradiation to induce photodegradation over the same time period (60 h). Excitation-emission matrices (EEMs) combined with parallel factor analysis (PARAFAC) identified four components: marine humic-like C1, terrestrial humic-like C2, soil fulvic-like C3, and tryptophan-like C4. Although the behaviours of these components during full-spectrum irradiation exhibited similar decreasing tendencies, three components (C1, C3, and C4) underwent direct photodegradation under UVB exposure, whereas C2 was more susceptible to UVA degradation. The diverse photoreactivities of the source-dependent components to different light treatments led to differing photochemical behaviours of other optical indices [aCDOM(355), aCDOM(254), SR, HIX, and BIX]. The results indicate that irradiation preferentially reduced the high humification degree or humic substance content of allochthonous DOM, and promoted the transformation from the allochthonous humic DOM components to recently produced components. Although values for the samples from different sources overlapped frequently, principal component analysis (PCA) indicated that the overall optical signatures could be linked to the original CDOM source features. The degradation of CDOM humification, aromaticity, molecular weight, and autochthonous fractions under exposure can drive the CDOM biogeochemical cycle in marine environments. These findings can aid in a better understanding of the effects of different combinations of light treatments and CDOM characteristics on CDOM photochemical processes.

Estrogen-responsive nitroso-proteome in uterine artery endothelial cells: role of endothelial nitric oxide synthase and estrogen receptor-ß.

Covalent adduction of a NO moiety to cysteines (S-nitrosylation or SNO) is a major route for NO to directly regulate protein functions. In uterine artery endothelial cells (UAEC), estradiol-17ß (E2) rapidly stimulated protein SNO that maximized within 10-30 min post-E2 exposure. E2-bovine serum albumin stimulated protein SNO similarly. Stimulation of SNO by both was blocked by ICI 182, 780, implicating mechanisms linked to specific estrogen receptors (ERs) localized on the plasma membrane. E2-induced protein SNO was attenuated by selective ERß, but not ERα, antagonists. A specific ERß but not ERα agonist was able to induce protein SNO. Overexpression of ERß, but not ERα, significantly enhanced E2-induced SNO. Overexpression of both ERs increased basal SNO, but did not further enhance E2-stimulated SNO. E2-induced SNO was inhibited by N-nitro-L-arginine-methylester and specific endothelial NO synthase (eNOS) siRNA. Thus, estrogen-induced SNO is mediated by endogenous NO via eNOS and mainly ERß in UAEC. We further analyzed the nitroso-proteomes by CyDye switch technique combined with two-dimensional (2D) fluorescence difference gel electrophoresis. Numerous nitrosoprotein (spots) were visible on the 2D gel. Sixty spots were chosen and subjected to matrix-assisted laser desorption/ionization-time of flight mass spectrometry. Among the 54 identified, nine were novel SNO-proteins, 32 were increased, eight were decreased, and the rest were unchanged by E2. Tandom MS identified Cys139 as a specific site for SNO in GAPDH. Pathway analysis of basal and estrogen-responsive nitroso-proteomes suggested that SNO regulates diverse protein functions, directly implicating SNO as a novel mechanism for estrogen to regulate uterine endothelial function and thus uterine vasodilatation.

Caveolin-1 orchestrates fibroblast growth factor 2 signaling control of angiogenesis in placental artery endothelial cell caveolae.

Fibroblast growth factor (FGF) receptor 1 (FGFR1) protein was expressed as the long and short as well as some truncated forms in ovine fetoplacental artery ex vivo and in vitro. Upon FGF2 stimulation, both the long and short FGFR1s were tyrosine phosphorylated and the PI3K/AKT1 and ERK1/2 pathways were activated in a concentration- and time- dependent manner in ovine fetoplacental artery endothelial (oFPAE) cells. Blockade of the PI3K/AKT1 pathway attenuated FGF2-stimulated cell proliferation and migration as well as tube formation; blockade of the ERK1/2 pathway abolished FGF2-stimulated tube formation and partially inhibited cell proliferation and did not alter cell migration. Both AKT1 and ERK1/2 were co-fractionated with caveolin-1 and activated by FGF2 in the caveolae. Disruption of caveolae by methyl-ß-cyclodextrin inhibited FGF2 activation of AKT1 and ERK1/2. FGFR1 was found in the caveolae where it physically binds to caveolin-1. FGF2 stimulated dissociation of FGFR1 from caveolin-1. Downregulation of caveolin-1 significantly attenuated the FGF2-induced activation of AKT1 and ERK1/2 and inhibited FGF2-induced cell proliferation, migration and tube formation in oFPAE cells. Pretreatment with a caveolin-1 scaffolding domain peptide to mimic caveolin-1 overexpression also inhibited these FGF2-induced angiogenic responses. These data demonstrate that caveolae function as a platform for regulating FGF2-induced angiogenesis through spatiotemporally compartmentalizing FGFR1 and the AKT1 and ERK1/2 signaling modules; the major caveolar structural protein caveolin-1 interacts with FGFR1 and paradoxically regulates FGF2-induced activation of PI3K/AKT1 and ERK1/2 pathways that coordinately regulate placental angiogenesis.

Controlled Pd(0)/t-Bu3P-catalyzed Suzuki cross-coupling polymerization of AB-type monomers with PhPd(t-Bu3P)I or Pd2(dba)3/t-Bu3P/ArI as the initiator.

Controlled Pd(0)/t-Bu(3)P-catalyzed Suzuki cross-coupling polymerizations of AB-type monomers via the chain-growth mechanism with an ArPd(t-Bu(3)P)I complex as the initiator are described. ArPd(t-Bu(3)P)I complexes, either prepurified or generated in situ from Pd(2)(dba)(3)/t-Bu(3)P/ArI (dba = dibenzylideneacetone) without separation/purification, were found to be efficient initiators in general for the controlled Suzuki cross-coupling polymerization, with narrow polydispersity indexes (PDIs) of 1.13-1.35 being observed. The Pd(2)(dba)(3)/t-Bu(3)P/p-BrC(6)H(4)I combination was identified as a highly robust initiator system, with PDIs of ≤1.20 in general and as low as 1.13 being obtained. Higher number-average molecular weights (M(n)) were achieved without a significant increase in the PDI (from 1.14 for a polymer with a M(n) = 9500 to 1.20 for a polymer with M(n) = 31,400) by using a smaller amount of the Pd(2)(dba)(3)/t-Bu(3)P/p-BrC(6)H(4)I initiator in the polymerization.

Compartmentalizing proximal FGFR1 signaling in ovine placental artery endothelial cell caveolae.

Caveolae orchestrate the dominant placental angiogenic growth factor fibroblast growth factor 2 (FGF2) signaling primarily via FGF receptor 1 (FGFR1) in placental artery endothelial cells; however, how the proximal FGF2/FGFR1 signaling is organized in the caveolae is obscure. We have shown in the present study that the FGFR substrate 2alpha (FRS2alpha) is physically associated with FGFR1, and both are targeted to the caveolae via interaction with caveolin-1 in ovine fetoplacental artery endothelial cells. Treatment with FGF2 rapidly stimulated time- and concentration-dependent FRS2alpha tyrosine phosphorylation and recruited the cytosolic growth factor receptor-bound protein 2 (GRB2)-GRB2-associated binding protein 1 (GAB1) complex to the caveolae, where they formed a ternary complex with FRS2alpha. Disruption of caveolae by cholesterol depletion with methyl-beta-cyclodextrin inhibited FGF2-induced FRS2alpha tyrosine phosphorylation, and it blocked the FGF2-induced recruitment of GRB2 and GAB1 to the caveolae and formation of the FRS2alpha-GRB2-GAB1 complex in the caveolae, as well as activation of the PI3K/AKT1 and MAPK1/2 pathways. Thus, these findings have demonstrated that the proximal fibroblast growth factor (FGF2/FGFR1) signaling is compartmentalized in the placental endothelial caveolae via the FGFR substrate 2α that mediates formation of a FRS2α-GRB2-GAB1 complex.