The mitogen-activated protein kinase (MAPK) cascades, in which the major components are MAPK, MAPK kinase (MAPKK), and MAPKK kinase (MAPKKK), are conserved eukaryotic signaling pathways (2, 7, 14, 46). The general function of the MAPK cascades is to link a variety of extracellular stimuli to nuclear responses, i.e., the modulation of gene expression (45). MAPK is activated by dual phosphorylation on threonine and tyrosine residues catalyzed by MAPKK, and MAPKK is activated by serine/threonine phosphorylation catalyzed by MAPKKK. In mammals, at least three MAPK cascades have been identified. The MAPKs in each pathway are ERK (extracellular signal-regulated kinase), JNK/SAPK (cJun N-terminal kinase/stress-activated protein kinase), and p38. The ERK cascade is mostly responsive to mitogenic and differentiation stimuli, whereas the JNK and p38 cascades are strongly activated by proinflammatory cytokines, such as interleukin 1 (IL-1) and tumor necrosis factor alpha (TNF-␣), and extracellular stresses, such as UV irradiation and osmotic shock (4,23,29,36).In the ERK cascade, Raf (Raf-1, A-Raf, and B-Raf), MEK (MEK1 and MEK2), and ERK (ERK1 and ERK2) correspond to MAPKKK, MAPKK, and MAPK, respectively (36). The p38 cascade contains p38␣/CSBP/RK/Mxi2 (12,25,37,56) and p38␤ (18) as MAPKs and MKK3 (9) and MKK6 (6,13,32,35,42) as MAPKKs, while in the JNK cascade the MAPKs are JNK1, JNK2, and JNK3 (also known as SAPK␥, SAPK␣, and SAPK␤, respectively) (8,11,19,22,31), and the MAPKKs are SEK1/MKK4/JNKK1 (9,26, 38) and MKK7/JNKK2 (33,44,48). The specificity of the MAPKKKs involved in the JNK and p38 cascades is less clear. For instance, the TAK1 (52), ASK1 (16), and MLK3 (43) MAPKKKs can activate both the JNK and p38 cascades, while the MEKK1 (28, 50, 53) and MEKK4 (10) MAPKKKs selectively activate the JNK cascade.The identification of numerous components of the MAPK cascades as described above suggests that there are a number of these distinct signaling pathways in cells. Furthermore, studies of JNK3-deficient mice (54) indicate the existence of a JNK3-specific cascade that cannot be complemented by the other JNK family members, even though JNK1, JNK2, and JNK3 exhibit over 80% identity, and these JNKs seem to be

MiR-10b is a novel prognostic marker in colorectal cancer. Moreover, the expression of miR-10b is a potential indicator of chemosensitivity to the common 5-FU-based chemotherapy regimen.

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We report that a novel sulfonylamino compound, 4-[2-(phenylsulfonylamino)ethylthio]-2,6-difluoro-phenoxyacetamide (PEPA), selectively potentiates glutamate receptors of the AMPA subtype. PEPA (1-200 M) dose dependently potentiated glutamateevoked currents in Xenopus oocytes expressing AMPA (GluRAGluRD), but not kainate (GluR6 and GluR6ϩKA2) or NMDA (1 ϩ ⑀1-⑀4), receptor subunits. PEPA was effective at micromolar concentrations and, in contrast to the action of cyclothiazide, preferentially modulated AMPA receptor flop isoforms. At 200 M, PEPA potentiated glutamate responses by 50-fold in oocytes expressing GluRC flop (EC 50 ϳ50 M) versus only threefold for GluRC flip ; a similar preference for flop isoforms was observed for other AMPA receptor subunits. Dose-response analysis for GluRC flop revealed that 100 M PEPA produced a sevenfold increase in AMPA receptor affinity for glutamate. PEPA produced considerably weaker potentiation of kainate-evoked than glutamate-evoked currents, suggesting modulation of the process of receptor desensitization. In human embryonic kidney 293 cells transfected with AMPA receptor subunits, PEPA either abolished or markedly slowed the rate of onset of desensitization and potentiated steady-state equilibrium currents evoked by glutamate with subunit (GluRC Ն GluRD Ͼ GluRA) and splice-variant (flop Ͼ flip) selectivity similar to that observed in oocytes. Our results show that PEPA is a novel, flop-preferring allosteric modulator of AMPA receptor desensitization at least 100 times more potent than aniracetam. Key words: glutamate receptors; AMPA; desensitization; alternative splicing; flip and flop; allosteric modulationAllosteric modulation of the three subtypes of ionotropic glutamate receptors-AM PA, kainate, and NMDA receptors-is produced by a diverse spectrum of agents, including lectins, a variety of drugs, polyamines, and divalent cations. The unusually strong modulation of AM PA receptors by the benzothiadiazine and pyrrolidinone compounds cyclothiazide, aniracetam, and their derivatives (Ito et al

Androgens play an important role in male sexual differentiation and development. The activity of androgens is mediated by an androgen receptor (AR), which binds to specific DNA recognition sites and regulates transcription. We describe here the isolation of two distinct rainbow trout cDNA clones, designated rtAR-␣ and rtAR-␤, which contain the entire androgen receptor coding region. Comparison of the predicted amino acid sequence of rtAR-␣ to that of rtAR-␤ revealed 85% identity. Interestingly, despite this high homology, rtAR-␣ activated transcription of an androgen-responsive reporter gene in co-transfection assays, but rtAR-␤ did not. These results suggest that rainbow trout contains two distinct isoforms of androgen receptors whose functions differ. The region of rtAR-␤ responsible for its inactivity was mapped to its ligand binding domain by analyzing chimeras of the rtAR-␣, rtAR-␤, and rtGR-I (glucocorticoid) receptors. Alteration of any one of three out of four segments within this domain restored activity.Extracts made from COS-1 cells transfected with an rtAR-␣ expression plasmid produced a high level of [ 3 H]mibolerone binding, whereas no binding was observed by extracts of cells transfected with an rtAR-␤ expression plasmid. These data demonstrate that the lack of transactivation activity of rtAR-␤ is due to its inability to bind hormone.In contrast to mammals, fish can undergo gonadal sex inversion in either direction by treatment with exogenous sex steroid if it is applied early enough during development (1, 2). These observations led to the postulate that androgens and estrogens are the substances responsible for sex differentiation of male and female fish, respectively (3), and has resulted in the development of protocols for the masculinization and feminization of large numbers of fish for experimental or economic purposes (1, 4, 5). The androgen receptor (AR) 1 is a critical mediator of male sexual differentiation and development in both fish and mammals. Structurally and functionally, the AR belongs to the superfamily of ligand-responsive transcription modifiers, which encompasses the receptors for the steroid and thyroid hormones. Like other nuclear receptors, steroid receptors are composed of three major functional domains: an NH 2 -terminal hypervariable transcriptional activation domain (TAD), a central highly conserved DNA binding domain (DBD) consisting of two Cys-Cys zinc finger motifs, and a COOH-terminal ligand binding domain (LBD) (6 -9). It has been reported that the AR regulates androgen target genes by binding to a specific DNA sequence, the androgen-responsive element (ARE; consensus ϭ 5Ј-GGTACANNNTGTTCT), which is similar to the glucocorticoid response element (12)(13)(14). The AR can either up-or downregulate the expression of androgen target genes, the outcome probably depending on interactions with specific adapters or co-activators (10, 11).At present, complete AR cDNAs have been cloned only from mammalian species (human, rat, and mouse) (6, 15). We have undertaken the isola...