RESUMO
Background: Dynamic, relational developmental systems-based models of development emphasize that developmentally-nurturant youth-adult relationships elicit in youth perceptions of being known and loved. Although such perceptions are foundations of positive youth development (PYD), such measures do not exist. Objective: We sought to create a theoretically-predicated measure of youth perceptions of being known and loved by capitalizing on data sets in two countries (Rwanda and El Salvador) wherein a multi-national study of PYD was being conducted by Compassion International (CI). Method: With Rwanda data (n = 1,204, M age = 11.84, 50% CI-supported), exploratory and confirmatory factor analyses enabled refining the measure for robustness and parsimony. Measures of intentional self-regulation, hopeful future expectations, transcendence, and contribution were used for validation of the known and loved measure within the nomological net of constructs proposed in the Lerner and Lerner PYD model. Confirmatory factor analyses supported the use of the model within the El Salvador data set (n = 1,205, M age = 13.03, 51% CI-supported). Results: Robust psychometric properties were established in both national settings. Measurement invariance was found across age, gender, urban-rural location, CI-enrollment status, and nations, and involved both mean differences and correlations among latent factors. Conclusions: The results provide evidence for a theory-predicated measure of youth perceptions of being known and loved and that scores for this construct covary within a nomological net specified in the Lerner and Lerner model of PYD. These findings serve international development organizations seeking theory-predicated measures for use in evaluating PYD programs in low- and middle-income countries. Supplementary Information: The online version contains supplementary material available at 10.1007/s10566-022-09725-6.
RESUMO
Mast cells play both effector and modulatory roles in a range of allergic and immune responses. The principal function of these cells is the release of inflammatory mediators from mast cells by degranulation, which involves a complex interplay of signalling molecules. Understanding the molecular architecture underlying mast cell signalling has attracted renewed interest as the capacity for therapeutic intervention through controlling mast cell degranulation is now accepted as a viable proposition. The dynamic regulation of signalling by protein phosphorylation is a well-established phenomenon and many of the early events involved in mast cell activation are well understood. Less well understood however are the events further downstream of receptor activation that allow movement of granules through the cytoskeletal barrier and docking and fusion of granules with the plasma membrane. Whilst a potential role for the protein phosphatase family of signalling enzymes in mast cell function has been accepted for some time, the evidence has largely been derived from the use of broad specificity pharmacological inhibitors and results often depend upon the experimental conditions, leading to conflicting views. In this review, we present and discuss the pharmacological and recent molecular evidence that protein phosphatases, and in particular the protein phosphatase serine/threonine phosphatase type 2A (PP2A), have major regulatory roles to play and may be potential targets for the design of new therapeutic agents.
Assuntos
Degranulação Celular , Mastócitos/fisiologia , Fosfoproteínas Fosfatases/metabolismo , Fosforilação , Asma/imunologia , Exocitose , Humanos , Transdução de SinaisRESUMO
Mast cells undergo cytoskeletal restructuring to allow secretory granules passage through the cortical actomyosin barrier to fuse with the plasma membrane and release inflammatory mediators. Protein phosphorylation is believed to regulate these rearrangements. Although some of the protein kinases implicated in this phosphorylation are known, the relevant protein phosphatases are not. At the peak rate of antigen-induced granule mediator release (2.5 min), protein phosphatases PP1 and PP2A, along with actin and myosin II, are transiently relocated to ruffles on the apical surface and a band at the peripheral edge of the cell. This leaves an area between the nucleus and the peripheral edge significantly depleted (3-5-fold) in these proteins. Phorbol 12-myristate 13-acetate (PMA) plus A23187 induces the same changes, at a time coincident with its slower rate of secretion. Coimmunoprecipitation experiments demonstrated a significantly increased association of myosin with PP1 and PP2A at the time of peak mediator release, with levels of association decreasing by 5 min. Jasplakinolide, an inhibitor of actin assembly, inhibits secretion and the cytoskeletal rearrangements. Surprisingly, jasplakinolide also affects myosin, inducing the formation of short rods throughout the cytoplasm. Inhibition of PP2A inhibited secretion, the cytoskeletal rearrangements, and led to increased phosphorylation of the myosin heavy and light chains at protein kinase C-specific sites. These findings indicate that a dynamic actomyosin cytoskeleton, partially regulated by both PP1 and PP2A, is required for mast cell secretion.
Assuntos
Depsipeptídeos , Mastócitos/enzimologia , Mastócitos/metabolismo , Miosinas/metabolismo , Fosfoproteínas Fosfatases/metabolismo , Actinas/metabolismo , Animais , Antineoplásicos/farmacologia , Calcimicina/farmacologia , Linhagem Celular , Membrana Celular/metabolismo , Proteínas do Citoesqueleto/metabolismo , Citoesqueleto/metabolismo , Inibidores Enzimáticos/farmacologia , Exocitose/fisiologia , Imunoglobulina E/farmacologia , Ionóforos/farmacologia , Mastócitos/citologia , Mastócitos/efeitos dos fármacos , Ácido Okadáico/farmacologia , Mapeamento de Peptídeos , Peptídeos Cíclicos/farmacologia , Ratos , Acetato de Tetradecanoilforbol/farmacologiaRESUMO
We have studied the role of src family tyrosine kinases in regulating synaptic transmitter release from rat brain synaptosomes by using two assays that measure different aspects of synaptic vesicle exocytosis: glutamate release (that directly measures exocytosis of vesicle contents) and release of FM 2-10 styryl dye (that is proportional to the time the synaptic vesicle is fused to the plasma membrane). Depolarisation was induced by KCl (30 mM) or 4-aminopyridine (4AP: 0.3mM) to induce release by full fusion (FF) exocytosis, or by 1 mM 4AP to induce release by both FF and kiss-and-run (KR)-like exocytosis. The src family selective inhibitor, PP1 (10 microM), increased KCl and 0.3 mM 4AP-evoked Ca2+ -dependent release of glutamate, but had little effect upon exocytosis evoked by 1mM 4AP. PP1 did not affect the release of FM 2-10 under any of the depolarisation conditions used. PP1 also had no effect on overall intracellular calcium levels, as measured by FURA2, suggesting that the effects of the inhibitor are downstream of calcium entry. At the same concentration the inactive analogue of this compound, PP3, had no effect on any measure. Immunoblotting with an antibody to phosphotyrosine revealed that phosphorylation of many synaptosomal proteins was reduced by PP1. The immunoreactivity of three protein bands increased upon depolarisation and this increase was blocked by PP1. Phosphorylation of src at tyrosine-416 was reduced by PP1 but changes in its phosphorylation did not correlate with the effects of PP1 on release. These results suggest one or more members of the src family of tyrosine kinases is a negative regulator of the KR mode of exocytosis in synaptosomes, perhaps by tonically inhibiting KR under normal stimulation conditions.
Assuntos
Encéfalo/enzimologia , Exocitose/fisiologia , Terminações Pré-Sinápticas/enzimologia , Transmissão Sináptica/fisiologia , Vesículas Sinápticas/enzimologia , Quinases da Família src/metabolismo , 4-Aminopiridina/farmacologia , Animais , Encéfalo/fisiopatologia , Sinalização do Cálcio/efeitos dos fármacos , Sinalização do Cálcio/fisiologia , Regulação para Baixo/efeitos dos fármacos , Regulação para Baixo/fisiologia , Inibidores Enzimáticos/farmacologia , Exocitose/efeitos dos fármacos , Retroalimentação Fisiológica/efeitos dos fármacos , Retroalimentação Fisiológica/fisiologia , Fura-2 , Ácido Glutâmico/metabolismo , Fusão de Membrana/efeitos dos fármacos , Fusão de Membrana/fisiologia , Proteínas do Tecido Nervoso/efeitos dos fármacos , Proteínas do Tecido Nervoso/metabolismo , Fosforilação/efeitos dos fármacos , Bloqueadores dos Canais de Potássio/farmacologia , Cloreto de Potássio/farmacologia , Terminações Pré-Sinápticas/efeitos dos fármacos , Terminações Pré-Sinápticas/metabolismo , Pirazóis/farmacologia , Compostos de Piridínio , Pirimidinas/farmacologia , Compostos de Amônio Quaternário , Ratos , Transmissão Sináptica/efeitos dos fármacos , Vesículas Sinápticas/efeitos dos fármacos , Sinaptossomos , Quinases da Família src/antagonistas & inibidoresRESUMO
Recent discoveries of different modes of exocytosis and a plethora of molecules involved in neurotransmitter release has resulted in demand for more rapid and efficient methods for monitoring endogenous glutamate release from various tissue sources. In this article, we describe a high throughput microplate version of the enzyme-linked fluorescence detection method for the measurement of released glutamate, which utilises glutamate dehydrogenase, and the reduction of NADP to NADPH. Previous versions of this method rely upon cuvette-based fluorimeters for detection that are limited by large sample volumes and small numbers of samples that can be measured simultaneously. Comparison between the two methods shows that the microplate assay has comparable performance to the cuvette-based assay but has the capacity to analyse many times more samples in a given run. This increased capacity provides improved experimental design opportunities, higher experimental throughput and better comparison between experimental conditions.
Assuntos
Técnicas Biossensoriais/métodos , Ensaio de Imunoadsorção Enzimática/métodos , Exocitose/fisiologia , Ácido Glutâmico/análise , Ácido Glutâmico/metabolismo , Espectrometria de Fluorescência/métodos , Sinaptossomos/metabolismo , Animais , Técnicas Biossensoriais/instrumentação , Encéfalo/metabolismo , Encéfalo/ultraestrutura , Células Cultivadas , Ensaio de Imunoadsorção Enzimática/instrumentação , Ratos , Espectrometria de Fluorescência/instrumentaçãoRESUMO
Asthma is characterised by antigen-mediated mast cell degranulation resulting in secretion of inflammatory mediators. Protein phosphatase 2A (PP2A) is a serine/threonine protein phosphatase composed of a catalytic (PP2A-C) subunit together with a core scaffold (PP2A-A) subunit and a variable, regulatory (PP2A-B) subunit. Previous studies utilising pharmacological inhibition of protein phosphatases have suggested a positive regulatory role for PP2A in mast cell degranulation. In support of this we find that a high okadaic acid concentration (1µM) inhibits mast cell degranulation. Strikingly, we now show that a low concentration of okadaic acid (0.1µM) has the opposite effect, resulting in enhanced degranulation. Selective downregulation of the PP2A-Cα subunit by short hairpin RNA also enhanced degranulation of RBL-2H3 mast cells, suggesting that the primary role of PP2A is to negatively regulate degranulation. PP2A-B subunits are responsible for substrate specificity, and carboxymethylation of the PP2A-C subunit alters B subunit binding. We show here that carboxymethylation of PP2A-C is dynamically altered during degranulation and inhibition of methylation decreases degranulation. Moreover downregulation of the PP2A-Bα subunit resulted in decreased MK2 phosphorylation and degranulation, whilst downregulation of the PP2A-B'δ subunit enhanced p38 MAPK phosphorylation and degranulation. Taken together these data show that PP2A is both a positive and negative regulator of mast cell degranulation, and this differential role is regulated by carboxymethylation and specific PP2A-B subunit binding.
Assuntos
Degranulação Celular/fisiologia , Mastócitos/fisiologia , Proteína Fosfatase 2/metabolismo , Subunidades Proteicas/metabolismo , Animais , Linhagem Celular Tumoral , Relação Dose-Resposta a Droga , Regulação para Baixo/efeitos dos fármacos , Metilação , Modelos Biológicos , Ácido Okadáico/farmacologia , Fosfoproteínas Fosfatases/genética , Fosfoproteínas Fosfatases/metabolismo , Fosfoproteínas Fosfatases/fisiologia , Fosforilação , RNA Interferente Pequeno/metabolismo , Ratos , Transfecção , Proteínas Quinases p38 Ativadas por Mitógeno/genética , Proteínas Quinases p38 Ativadas por Mitógeno/metabolismoRESUMO
Oncogenic mutations of the receptor tyrosine kinase c-KIT play an important role in the pathogenesis of gastrointestinal stromal tumors, systemic mastocytosis, and some acute myeloid leukemias (AML). Although juxtamembrane mutations commonly detected in gastrointestinal stromal tumor are sensitive to tyrosine kinase inhibitors, the kinase domain mutations frequently encountered in systemic mastocytosis and AML confer resistance and are largely unresponsive to targeted inhibition by the existing agent imatinib. In this study, we show that myeloid cells expressing activated c-KIT mutants that are imatinib sensitive (V560G) or imatinib resistant (D816V) can inhibit the tumor suppressor activity of protein phosphatase 2A (PP2A). This effect was associated with the reduced expression of PP2A structural (A) and regulatory subunits (B55alpha, B56alpha, B56gamma, and B56delta). Overexpression of PP2A-Aalpha in D816V c-KIT cells induced apoptosis and inhibited proliferation. In addition, pharmacologic activation of PP2A by FTY720 reduced proliferation, inhibited clonogenic potential, and induced apoptosis of mutant c-KIT(+) cells, while having no effect on wild-type c-KIT cells or empty vector controls. FTY720 treatment caused the dephosphorylation of the D816V c-KIT receptor and its downstream signaling targets pAkt, pSTAT5, and pERK1/2. Additionally, in vivo administration of FTY720 delayed the growth of V560G and D816V c-KIT tumors, inhibited splenic and bone marrow infiltration, and prolonged survival. Our findings show that PP2A inhibition is essential for c-KIT-mediated tumorigenesis, and that reactivating PP2A may offer an attractive strategy to treat drug-resistant c-KIT(+) cancers.
Assuntos
Leucemia Mieloide Aguda/enzimologia , Proteína Fosfatase 2/antagonistas & inibidores , Proteínas Proto-Oncogênicas c-kit/metabolismo , Idoso , Animais , Apoptose/efeitos dos fármacos , Processos de Crescimento Celular/fisiologia , Linhagem Celular Tumoral , Ativação Enzimática , Feminino , Cloridrato de Fingolimode , Humanos , Leucemia Mieloide Aguda/tratamento farmacológico , Masculino , Camundongos , Camundongos Endogâmicos DBA , Fosforilação , Propilenoglicóis/farmacologia , Proteína Fosfatase 2/biossíntese , Proteína Fosfatase 2/genética , Proteína Fosfatase 2/metabolismo , Subunidades Proteicas , Proteínas Proto-Oncogênicas c-kit/genética , Transdução de Sinais , Esfingosina/análogos & derivados , Esfingosina/farmacologiaAssuntos
Fosfoproteínas Fosfatases/metabolismo , Animais , Citoesqueleto/enzimologia , Inibidores Enzimáticos/farmacologia , Inflamação , Cinética , Leucemia Basofílica Aguda/enzimologia , Leucemia Basofílica Aguda/patologia , Microscopia de Fluorescência/métodos , Miosinas/isolamento & purificação , Fosfoproteínas Fosfatases/isolamento & purificação , Ratos , Células Tumorais Cultivadas , beta-N-Acetil-Hexosaminidases/metabolismoAssuntos
Inibidores Enzimáticos/farmacologia , Fosfoproteínas Fosfatases/antagonistas & inibidores , Piranos , Compostos de Espiro , Alcenos/química , Alcenos/farmacologia , Alcenos/uso terapêutico , Antibióticos Antineoplásicos/química , Antibióticos Antineoplásicos/farmacologia , Antibióticos Antineoplásicos/uso terapêutico , Antifúngicos/química , Antifúngicos/farmacologia , Antifúngicos/uso terapêutico , Cantaridina/química , Cantaridina/uso terapêutico , Cristalografia por Raios X , Ciclosporina/química , Ciclosporina/farmacologia , Ciclosporina/uso terapêutico , Inibidores Enzimáticos/química , Inibidores Enzimáticos/uso terapêutico , Humanos , Microcistinas , Modelos Moleculares , Ácido Okadáico/química , Ácido Okadáico/farmacologia , Ácido Okadáico/uso terapêutico , Peptídeos Cíclicos/química , Peptídeos Cíclicos/farmacologia , Peptídeos Cíclicos/uso terapêutico , Fosfoproteínas Fosfatases/metabolismo , Polienos , Pironas , Relação Estrutura-AtividadeRESUMO
Autophosphorylation of Ca(2+)-calmodulin stimulated protein kinase II (CaMKII) at two sites (Thr286 and Thr305/306) is known to regulate the subcellular location and activity of this enzyme in vivo. CaMKII is also known to be autophosphorylated at Thr253 in vitro but the functional effect of phosphorylation at this site and whether it occurs in vivo, is not known. Using antibodies that specifically recognize CaMKII phosphorylated at Thr253 together with FLAG-tagged wild type and phospho- and dephospho-mimic mutants of alpha-CaMKII, we have shown that Thr253 phosphorylation has no effect on either the Ca(2+)-calmodulin dependent or autonomous kinase activity of recombinant alpha-CaMKII in vitro. However, the Thr253Asp phosphomimic mutation increased alpha-CaMKII binding to subcellular fractions enriched in post-synaptic densities (PSDs). The increase in binding was similar in extent, and additive, to that produced by phosphorylation of Thr286. Thr253 phosphorylation was dynamically regulated in intact hippocampal slices. KCl induced depolarisation increased Thr253 phosphorylation and the phospho-Thr253-CaMKII was specifically recovered in the subcellular fraction enriched in PSDs. These results identify Thr253 as an additional site at which CaMKII is phosphorylated in vivo and suggest that this dynamic phosphorylation may regulate CaMKII function by altering its distribution within the cell.
Assuntos
Proteínas Quinases Dependentes de Cálcio-Calmodulina/metabolismo , Membranas Sinápticas/metabolismo , Treonina/metabolismo , Trifosfato de Adenosina/farmacologia , Animais , Western Blotting/métodos , Encéfalo/citologia , Proteína Quinase Tipo 2 Dependente de Cálcio-Calmodulina , Proteínas Quinases Dependentes de Cálcio-Calmodulina/química , Humanos , Proteínas Mutantes/metabolismo , Fosforilação , Mudanças Depois da Morte , Cloreto de Potássio/farmacologia , Ligação Proteica/efeitos dos fármacos , Ligação Proteica/fisiologia , Ensaio Radioligante/métodos , Ratos , Ratos Sprague-Dawley , Frações Subcelulares/metabolismo , Membranas Sinápticas/efeitos dos fármacos , Fatores de TempoRESUMO
Protein phosphatases are integrally associated with the regulation of cellular signaling. The mechanisms underlying the specific regulatory roles are likely to be unique to each cell system. Nevertheless, analysis of phosphatase regulation in a number of systems has identified phosphatase targeting through association with a wide range of binding partners to be a fundamental mechanism of regulation. Using protein phosphatase 2A (PP2A) as an example, this snapshot summarizes these fundamental mechanisms of protein phosphatase regulation.
Assuntos
Fosfoproteínas Fosfatases/metabolismo , Animais , Humanos , Modelos Moleculares , Fosfoproteínas Fosfatases/química , Ligação Proteica , Proteína Fosfatase 2 , Estrutura Quaternária de Proteína , Transdução de SinaisRESUMO
This study was undertaken to characterise the protein phosphatases in bovine adrenal chromaffin cells acting on tyrosine hydroxylase. Cells were pre-labelled with 32Pi and permeabilized with digitonin. The extent of dephosphorylation of Ser-8, Ser-19, Ser-31 and Ser-40 on tyrosine hydroxylase was found to be 30%, 38%, 37% and 71% respectively over 5 min. For Ser-19, Ser-31 and Ser-40 the dephosphorylation was entirely due to protein phosphatase 2A, as the dephosphorylation could be completely blocked by microcystin, but not by the protein phosphatase I inhibitory peptide. Permeabilization did not change the distribution of protein phosphatase 2A or tyrosine hydroxylase, or the activity of PP2A, from that occurring in intact cells. The dephosphorylation of Ser-8 was not altered by any inhibitor, suggesting the involvement of other protein phosphatases. The method developed here can be used to determine the protein phosphatases acting on substrates in conditions closely approximating those in situ, including the endogenous state of substrate phosphorylation and phosphatase location.
Assuntos
Células Cromafins/enzimologia , Fosfoproteínas Fosfatases/metabolismo , Tirosina 3-Mono-Oxigenase/metabolismo , Medula Suprarrenal/enzimologia , Animais , Bovinos , Membrana Celular/enzimologia , Permeabilidade da Membrana Celular , Células Cultivadas , Fosfatos/metabolismo , Fosfoproteínas/metabolismo , Proteína Fosfatase 2RESUMO
The inhibitors okadaic acid (OA), fostriecin (FOS) and cyclosporin A (CsA), were used to investigate the roles of protein phosphatases in regulating exocytosis in rat brain synaptosomes by measuring glutamate release and the release of the styryl dye FM 2-10. Depolarization was induced by 30 mM KCl, or 0.3 mM or 1 mM 4-aminopyridine (4AP). OA and FOS produced a similar partial inhibition of KCl- and 0.3 mM 4AP- evoked exocytosis in both assays, but had little effect upon exocytosis evoked by 1 mM 4AP. In contrast, CsA had no effect upon KCl- and 0.3 mM 4AP-evoked exocytosis, but significantly enhanced glutamate release but not FM 2-10 dye release evoked by 1 mM 4AP. None of the phosphatase inhibitors changed calcium signals from FURA-2-loaded synaptosomes either before or after depolarization. Pretreatment with 100 nM phorbol 12-myristate 13-acetate abolished the inhibitory effect of OA on exocytosis induced by 0.3 mM 4AP. Taken together, these results show that exocytosis from synaptosomes has a phosphatase-sensitive and phosphatase-insensitive component, and that there are two modes of phosphatase-sensitive exocytosis that can be elicited by different depolarization conditions. Moreover, these two modes are differentially sensitive to phosphatase 2A and 2B.
Assuntos
Calcineurina/química , Exocitose/fisiologia , Fosfoproteínas Fosfatases/química , Sinaptossomos/enzimologia , Animais , Química Encefálica , Calcineurina/metabolismo , Inibidores de Calcineurina , Cálcio/análise , Cálcio/metabolismo , Ciclosporina/farmacologia , Inibidores Enzimáticos/farmacologia , Exocitose/efeitos dos fármacos , Corantes Fluorescentes/química , Ácido Glutâmico/metabolismo , Fosfoproteínas Fosfatases/antagonistas & inibidores , Fosfoproteínas Fosfatases/metabolismo , Proteína Fosfatase 2 , Ratos , Sinaptossomos/química , Sinaptossomos/efeitos dos fármacosRESUMO
Tyrosine hydroxylase (TH) is the rate-limiting enzyme in the synthesis of catecholamines. It is dephosphorylated by protein phosphatase (PP) 2A and PP2C. In this study we used a fixed amount of bacterially expressed rat TH (5 microM), phosphorylated only at serine 40 (pSer40TH), to determine the PP activities against this site that are present in extracts from the bovine adrenal cortex, adrenal medulla, adrenal chromaffin cells and rat striatum. We found that PP2C was the main TH phosphatase activity in extracts from the adrenal medulla and adrenal chromaffin cells. In adrenal cortex extracts PP2C and PP2A activities toward pSer40TH did not differ significantly. PP2A was the main TH phosphatase activity in extracts from rat striatum. Kinetic studies with extracts from adrenal chromaffin cells showed that when higher concentrations of pSer40TH (> 5 microM) were used the activity of PP2C increased more than the activity of PP2A. PP2C was maximally activated by 1.25 mM Mn2+ and by 5 mM Mg2+ but was inhibited by calcium. Our data suggest a more important role for PP2C than was previously suggested in the dephosphorylation of serine 40 on TH.
Assuntos
Células Cromafins/metabolismo , Fosfoproteínas Fosfatases/metabolismo , Tirosina 3-Mono-Oxigenase/metabolismo , Córtex Suprarrenal/química , Córtex Suprarrenal/metabolismo , Medula Suprarrenal/química , Medula Suprarrenal/metabolismo , Animais , Cálcio/farmacologia , Bovinos , Extratos Celulares/química , Células Cultivadas , Células Cromafins/química , Células Cromafins/citologia , Corpo Estriado/química , Corpo Estriado/metabolismo , Ativação Enzimática/efeitos dos fármacos , Cinética , Magnésio/farmacologia , Manganês/farmacologia , Fosfatos/metabolismo , Fosforilação , Proteína Fosfatase 2C , Serina/metabolismo , Especificidade por SubstratoRESUMO
Modulation of exocytosis is integral to the regulation of cellular signalling, and a variety of disorders (such as epilepsy, hypertension, diabetes and asthma) are closely associated with pathological modulation of exocytosis. Emerging evidence points to protein phosphatases as key regulators of exocytosis in many cells and, therefore, as potential targets for the design of novel therapies to treat these diseases. Diverse yet exquisite regulatory mechanisms have evolved to direct the specificity of these enzymes in controlling particular cell processes, and functionally driven studies have demonstrated differential regulation of exocytosis by individual protein phosphatases. This Review discusses the evidence for the regulation of exocytosis by protein phosphatases in three major secretory systems, (1) mast cells, in which the regulation of exocytosis of inflammatory mediators plays a major role in the respiratory response to antigens, (2) insulin-secreting cells in which regulation of exocytosis is essential for metabolic control, and (3) neurons, in which regulation of exocytosis is perhaps the most complex and is essential for effective neurotransmission.
Assuntos
Exocitose/fisiologia , Fosfoproteínas Fosfatases/fisiologiaRESUMO
High pressure Diels-Alder reactions of furan and dimethylmaleate, and thiophene and maleimide resulted in two cantharidin analogues, 3 and 6 possessing PP1 selectivity (>40- and >30-fold selectivity) over PP2A. Both compounds exhibited moderate PP1 activity, 3 IC(50) 50 microM and 6 IC(50) 12.5 microM. Interestingly, the corresponding mono-ester derivatives of 3 showed no such selectivity.