Natural product extracts have proven to be a rich source of small molecules that potently inhibit the catalytic activity certain PPP-family ser/thr protein phosphatases. To date, list inhibitors includes okadaic acid (produced by marine dinoflagelates, Prorocentrum sp. and Dinophysis sp.), calyculin A, dragmacidins (isolated from sponges), microcystins, nodularins (cyanobacteria, Microcystis Nodularia tautomycin, tautomycetin, cytostatins, phospholine, leustroducsins, phoslactomycins,...

Cantharidin, a natural toxicant of blister beetles, is strong inhibitor protein phosphatases types 1(PP1) and 2A (PP2A). Like okadaic acid, cantharidin inhibits the activity purified catalytic subunit PP2A (IC 50 = 0.16 μM) at lower concentration than that PPI 1.7 only phosphatase type 2B (PP2B) high concentrations. Dose‐inhibition studies conducted with whole cell homogenates indicate also native forms these enzymes. Thus, cantharidin, which economical readily available, may be useful as an...

Fostriecin, an antitumor antibiotic produced by Streptomyces pulveraceus , is a strong inhibitor of type 2A (PP2A; IC 50 3.2 nM) and weak 1 (PP1; 131 μM) serine/threonine protein phosphatases. Fostriecin has no apparent effect on the activity PP2B, dose‐inhibition studies conducted with whole cell homogenates indicate that fostriecin also inhibits native forms PP1 PP2A. Studies recombinant PP1/PP2A chimeras okadaic acid have different binding sites.

Ligand-induced glucocorticoid receptor (GR) activation has recently been linked to the inhibition of cell proliferation via transcriptional induction p21WAF1/Cip1, which functions as a universal inhibitor cyclin-dependent protein kinases. Herein, we identify Ser/Thr phosphatase (PP5) that promotes cellular by inhibiting both and p53-mediated signaling pathways leading p21WAF1/Cip1-mediated growth arrest. The suppression PP5 expression (1) markedly increases association GR with its cognate...

Mitogen-activated protein kinase (MAPK) signaling cascades are multifunctional networks that influence cell growth, differentiation, apoptosis, and cellular responses to stress. Since the activation/propagation of MAPK requires sequential phosphorylation many downstream proteins, phosphatases dephosphorylate MAPKs represent critical elements in control MAPK-signaling networks. Here we show hypoxia induces a transient increase activity apoptosis signal-regulating 1 (ASK-1), MAPKKK responds...

A novel serine/threonine protein phosphatase (PPase) designated PP7 was identified from cDNA produced human retina RNA. has a molecular mass of ∼75 kDa, and the deduced amino acid sequence contains catalytic core domain that possesses all invariant motifs PP1, PP2A, PP2B, PP4, PP5, PP6 gene family. However, unique N- C-terminal regions shares <35% identity with other known PPases. The region multiple Ca2+ binding sites (i.e. EF-hand motifs). This is similar to Drosophila retinal degeneration...

Key derivatives and analogues of fostriecin were prepared examined that revealed a fundamental role for the unsaturated lactone confirmed essential nature phosphate monoester. Thus, an identical 200-fold reduction in protein phosphatase 2A (PP2A) inhibition is observed with either saturated (7) or analogue lacks entire (15). This increase PP2A attributable to potentially may be due reversible C269 alkylation within PP β12−β13 active site loop accounting PP2A/4 potency selectivity.

Serine/threonine protein phosphatase-5 (PP5) affects many signaling networks that regulate cell growth and cellular responses to stress. Here we report the crystal structure of PP5 catalytic domain (PP5c) at a resolution 1.6 A. From this propose mechanism for PP5-mediated hydrolysis phosphoprotein substrates, which requires precise positioning two metal ions within conserved Asp271-M1:M2-W1-His427-His304-Asp274 motif (where M1 M2 are metals W1 is water molecule). The PP5c provides structural...

A novel serinelthreonine protein phosphatase is identified, and the catalytic subunit, obtained from a detergent extraction of pellet generated by 100,000 % g centrifugation whole bovine brain homogenate, purified characterized.The phosphatase, designated as PP3, has M, 36,000, does not require divalent cations for activity, stimulated rather than inhibited inhibitor 2, both okadaic acid microcystin-LR with an intermediate ICeo compared to type 1 2A phosphatases, preferentially...

Affinity purification coupled to mass spectrometry (AP-MS) represents a powerful and proven approach for the analysis of protein-protein interactions. However, detection true interactions proteins that are commonly considered background contaminants is currently limitation AP-MS. Here using spectral counts new statistical tool, Significance Analysis INTeractome (SAINT), interaction between serine/threonine protein phosphatase 5 (PP5) chaperonin, heat shock 90 (Hsp90), discerned. Furthermore,...

Abstract Earlier we identified PPP2CA, which encodes for the α-isoform of protein phosphatase 2A (PP2A) catalytic subunit, as one downregulated genes in androgen-independent prostate cancer. PP2A is a serine/threonine and potent tumor suppressor involved broad cellular functions; however, its role cancer has not yet been determined. Here, have investigated effect activity modulation on growth cells. Our data show that PPP2CA expression (C4-2) cells compared with androgen-dependent (LNCaP)...

Selective inhibitors for each serine/threonine phosphatase (PPP) are essential to investigate the biological actions of PPPs and guide drug development. Biologically diverse organisms (e.g., cyanobacteria, dinoflagellates, beetles) produce structurally distinct toxins that catalytic PPPs. However, most exhibit little selectivity, typically inhibiting multiple family members with similar potencies. Thus, use these as chemical tools study relationship between individual their substrates, how...

Abstract LB-100 is an experimental cancer therapeutic with cytotoxic activity against cells in culture and antitumor animals. The first phase I trial (NCT01837667) evaluating recently concluded that safety efficacy parameters are favorable for further clinical testing. Although widely reported as a specific inhibitor of serine/threonine phosphatase 2A (PP2AC/PPP2CA:PPP2CB), we could find no evidence the published literature demonstrating engagement PP2A vitro, cultured cells, or Rather,...

Corticosteroid insensitivity (CSI) represents a profound challenge in managing patients with asthma. We recently demonstrated that short exposure of airway smooth muscle cells (ASMCs) to proasthmatic cytokines drastically reduced their responsiveness glucocorticoids (GCs), an effect was partially mediated via interferon regulatory factor-1, suggesting the involvement additional mechanisms (Am J Respir Cell Mol Biol 2008;38:463-472). Although GC receptor (GR) can be phosphorylated at multiple...

Functional genomic approaches have facilitated the discovery of rare genetic disorders and improved efforts to decipher their underlying etiology. PPP2R5D-related disorder is an early childhood onset condition characterized by intellectual disability, hypotonia, autism-spectrum disorder, macrocephaly, dysmorphic features. The caused de novo single nucleotide changes in PPP2R5D, which generate heterozygous dominant missense variants. PPP2R5D known encode a B'-type (B'56δ) regulatory subunit...

Type-1 protein serine/threonine phosphatases (PP1) are uniquely inhibited by the mammalian proteins, inhibitor-1 (I-1), inhibitor-2 (I-2), and nuclear inhibitor of PP1 (NIPP-1). In addition, several natural compounds inhibit both type-2 phosphatase, PP2A. Deletion C-terminal sequences that included β12-β13 loop attenuated inhibition resulting PP1α catalytic core I-1, I-2, NIPP-1, toxins, including tautomycin, microcystin-LR, calyculin A, okadaic acid. Substitution from PP2A subunit produced...

Background —The role of protein phosphatases (PPs) during ischemic preconditioning in the rabbit heart was examined. Methods and Results —Fostriecin, a potent inhibitor PP2A, administered to isolated hearts starting either 15 minutes before or 10 after onset 30-minute period regional ischemia continuing until reperfusion. After 2 hours reperfusion, infarct size measured with triphenyltetrazolium chloride. In second study cardiomyocytes, effect fostriecin pretreatment assessed by measuring...

In most cells glucocorticoid receptors (GR) reside predominately in the cytoplasm. Upon hormone binding, GR translocates into nucleus, where hormone-activated GR-complex regulates transcription of GR-responsive genes. Serine/threonine protein phosphatase type 5 (PP5) associates with GR-heat-shock protein-90 complex, and suppression PP5 expression ISIS 15534 stimulates activity reporter plasmids, without affecting binding to GR. To further characterize mechanism by which affects GR-induced...

The technique of freeze fracture was used to visualize triglyceride (TG) hydrolysis and the production lipolytic products (LPs) in vitro vivo presence bile salts (BS). Three systems were investigated: pure (oleic acid monoolein) a salt (taurodeoxycholate (TDC)), produced from TG by pancreatic lipase variety salts, intestine killifish, Fundulus heteroclitus, after fat feeding. In vitro, lamellae (4-5 nm thick with 0-8-nm water spacings) appeared on surface droplets all preparations LP/BS...